Consumer Products – Thieo Hogen-Esch, Massoud Pirbazari, Varadarajan Ravindran, Hayriye Merve Yurdacan, Woonhoe Kim, University of Southern California USC
Abstract for “High-performance membranes for water reclamation with polymeric and nanomaterials.”
“Water permeable membrane is available for water purification applications, including ultrafiltration, nanofiltration, and reverse osmosis. The water permeable membrane comprises a porous support, and a composite layer that is disposed over it. The composite layer contains graphene oxide, which is dispersed in a polymer matrix.
Background for “High-performance membranes for water reclamation with polymeric and nanomaterials.”
“Conventional separations process recover, isolate and purify products from virtually all manufacturing spheres. This includes chemicals, pharmaceuticals and petroleum as well as electronics, automobiles, and aerospace. These processes are energy-intensive and costly and account for between 40 and 70 percent of capital and operational costs. They also account for 45 percent to 45 percent of the energy costs in the petroleum and chemical industries, excluding any pollution control costs. Industries have been shifting their attention from treatment and pollution to water recovery, reuse, and recycling in recent years. This is mainly due to severe water shortages and droughts as well as stricter environmental regulations, rising treatment cost, and spatial constraints. Membrane technology offers a viable, more efficient alternative to traditional separations that also has significant economic and environmental benefits. Due to their many applications in commercial, industrial, and environmental settings, processes such as reverse osmosis, microfiltration, ultrafiltration and nanofiltration have received significant attention.
“Membrane technologies have to overcome many technological hurdles before widespread implementation. These include membrane fouling and permeate flux decline. They also need to be able to separate (reject) well and are not durable. These issues require innovations and development in membrane production that is more resistant to fouling, has higher permeate flux, and displays better selectivity.
“Semipermeable RO membrane mediated processes are one of the most efficient methods to remove salts (Na, monovalent and divalentions ions), and other aqueous contaminants. Because of their high salt rejection and pH tolerance, thin-film composite polyamide membranes (PA) dominate the market. These membranes have low water permeabilities due to their rigid, cross-linked structure. These membranes are also susceptible to temperature changes, low durability and sensitivity to microbial attack (biodegradation), as well as a lack of resistance against different types of fouling. Due to the high pressures needed for sustained and enhanced water flux, energy demands are high.
“The incorporation of nano-sized objects, such as carbon nanotubes or zeolites, into RO membranes has been attempted to improve their performance, but the results have been limited (Li L. et al. J. Membr. Sci., 2004, 243, 401-404; Li L et al., Desalination, 2008, 228, 217-225; Fornasiero F et al., Proc. Natl Acad. Sci. USA, 2008, 105, 17250-17255; Holt J K et al., Science, 2006, 312, 1034-1037).”
“There is a need to improve RO membrane structures and methods of making them.”
The infusion of nanoobjects (NOs), into polymeric matrixes to create nanocomposites is a promising frontier in membrane technology. This could lead to significant improvements in aqueous transport as well as fouling resistance. Examples include the use of carbon nanotubes (CNTs), which facilitate micro-transport of water. CNTs can be used to increase polymer hydrophilicities by incorporating polar functional groups. This reduces their potential for organic, inorganic, and particulate fouling. CNTs have antibacterial properties, which can significantly reduce biofilm formation and biological fouling. Their use can also lead to stronger membranes that are less susceptible to mechanical failures (Xie et. al., Materials Science and Engineering 49, 89-112, 2005). Infusion of nanomaterials in polymeric materials can lead to significant energy savings as well as lower operation and maintenance costs. Zeolite nanocrystals (ZNCs), for instance, have been shown to increase membrane hydrophilicity as well as aqueous non viscous micro-transport characteristics (Lind and al., Langmuir 25 (17), 10139-10145 2009). A combination of nanomaterials could have a synergistic effect on water transport.
“The embedded materials described herein target new types of polymeric and nanomaterial-based membranes for use in integrated membrane systems, such as the membrane bioreactor process (MBR), for water purification, groundwater recharge, and water reuse.
“Integrated systems like MBR have demonstrated excellent potential for water reclamation and reuse, groundwater replenishment, and other similar applications. The technology can be made more economical and efficient by using superior membranes that have better anti-fouling and aqueous transport. They can reduce operating costs by a significant amount, and even lower energy costs. Continuous flow hybrid MB R systems offer several technical advantages over traditional biological processes in environmental applications. They are small and footprint-friendly, require very long solids retention times and efficiently retain particulates, colloids and contaminants. To meet groundwater recharge requirements, the treated effluent must be low in suspended solids and chemical oxygen demand (COD), biochemical oxygen demand(BOD), total organic carbon, (TOC), and most pathogens. Modern, computerized and programmable control systems can make the MBR process more compact, efficient, and economically feasible. An adsorbent like powder activated carbon will be used to defoul membranes and maintain high permeate flows (Pirbazari and Pirbazari in Water Research, 30, 11), 2691-2706, 1996. Williams and Pirbazari in Water Research 41 (17), 3880-3893, 2007; Williams et.al., Chemical Engineering Science 84, 494-511 (2012). The adsorbent will also be able to remove trace levels or residual micro-pollutants, including those that disrupt hormones (EDCs), such as pesticides, pharmaceuticals, and solvents, during water reclamation (Snyder and al., Desalination), 202(1-3), 152-181, 2007).
“Nanofiltration is a widely-used technology in wastewater treatment and water reclamation. Ultrafiltration and microfiltration are used to pre-treat nanofiltration membranes against biological and organic fouling. However, nanofiltration membranes or reverse osmosis membranes can be prone to inorganic fouling and inorganic scaling. This is due to the deposition of inorganic precipitates such as calcium carbonate, magnesium sulfurate, and many others. The membrane must be capable to repel cations like calcium and magnesium ions, as well as anions like sulfates or carbonates. This will reduce the possibility of membrane scaling from precipitation. The present invention employs nanomaterial and membrane polymer formulations in some embodiments to reduce organic scaling. This is done by using surface charge mechanisms.
“Reduction of all inorganic fouling is an important consideration when preparing nanofiltration membranes or reverse osmosis membranes using polymer blends that include the infusion of nanomaterials. The rejection and organic fouling potential of nanofiltration membranes for wastewater treatment and water reclamation are determined by the molecular sizes and weights of organic constituents. Imai et. al. (2002) extensively discussed this topic. These six main components of dissolved organic matter are: (1) Aquatic Humic substances (AHS), (2) Hydrphobic bases [HOB], (3) Hydrophobic neutrals (?HON?), (4) Hydrophilic acid (HIA), five Hydrophilic basess (HIB), and six Hydrophilic neutrals (?HIN?). HON and HIN, while not acidic or basic, are neutral in nature. These aspects should be considered carefully from the perspective of organic fouling membranes, especially nanofiltration membranes that can best remove them.
“The most widely used polymeric membrane materials in conventional applications are the following: cellulose acetate, nitrocellulose, and cellulose esters (CA, CN, and CE), polytetra-fluoro-ethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyacrylonitrile (PAN), polyamides, polyimides, polyvinyl chloride (PVC), polysulfone (PS), polyether sulfone (PES) polyether sulfone (PES), polyethylene and polypropylene (PE and PP).”
“Several studies have been done to improve the hydrophilic properties of polymers, especially in the case PS and PES membranes. (Richards, et al. 2012). This has been done by: (1) mixing polymers such as PS with hydrophilic nanoparticles like SiO2, ZnO2, or TiO2; (2) grafting polymers such as PS and PES with more waterphilic or monomers; (3) coating the polymer in more hydrophilic materials. The advantages of blending polymers include excellent separation performance, chemical resistance, thermal resistance, pH tolerance and general adaptability to harsh environments such as wastewater treatment and water reclamation (Richards and al., 2012).
“An important aspect of membrane development is the consideration and application of new polymer formulations. For example, variations of this invention contemplate the use of polyvinylidene dimeride (PVDF), and polystyrene sulfuric acid (PSSA), with or without graphene, or graphene oxide. These copolymer and polymer blends are hydrophilic and hydrophobic functional groups. The latter is found on the outer surfaces. These types of polymer blends are used to achieve the desirable micro-structural and mechanical transportive, as well as fouling resistance properties of the polymer components. Use of polymer mixtures like those of PVDF or polystyrene sulfuric acid (PSSA), increases the mechanical strength, durability and robustness of the fabricated membranes. Variation in composition and blending will also allow for flexibility and tuneability of membrane pore sizes. This can enhance water molecules’ transport properties and reduce fouling potential. Fouling can be reduced on both the surface and inside of the membranes. Polymer formulations should improve the membrane’s mechanical strength, durability, longevity, chemical tolerance, pH tolerance, cleanability, and micro-structural integrity.
“In recent years, many nanoparticles were incorporated into membranes, such as those of metals, metal oxides, or non-metal oxygens, including SiO2, Al2O3, ZeO2, ZnO2, ZrO2, and Ag, as well as zeolites and single and multiwalled carbotubes (CNTs), for various purposes, including wastewater treatment. Richards et. al (2012) have reviewed these issues extensively. They can treat two types of fouling: organic fouling from natural organic matter and synthetic material, and biological fouling caused by microorganisms, including their exudates. These nanoparticles can also improve the aqueous transport properties. Li et al. (2006) found that the PES-TiO2 membrane’s water flux was significantly increased by the addition of titanium dioxide nanoparticles. However, the flux was dependent upon the concentration of nanoparticles. The researchers also found that nanoparticles are very volatile and can be easily agglomerated due to their high diffusivity. Because of their biocidal and bactericidal properties, these nanoparticles can be used to control biological fouling (Zodrow and Richards, 2009; Richards and Al, 2012). Maximous et al. Maximous et al. Bae and Tak (2005) found that titanium dioxide (TiO2) was not only attracted to the membrane’s surface, but also to the membrane pores. This led to decreased membrane permeability and higher filtration resistance. This is a significant factor in membrane synthesis. These studies revealed that metal and metal oxide nanoparticles were more attracted to water molecules than plain polymeric membranes. Therefore, their immunization in polymer matrixes was beneficial for water flux and fouling control. Use of carbon-based nanomaterials like graphene (G), CNTs (CNT), and grapheneoxide (GO) may have a greater impact on the performance of polymeric membranes in terms of aqueous transportation and fouling control. Because of the inherent characteristics of GO, it is expected to have a greater impact on impregnation polymeric matrices. Use of nanomaterials like G or GO in polymer formulations at different concentrations is intended to promote ant-friction microflow water transport, biocidal characteristics (regarding the resistance to biological fouling, destruction of pathogenic organisms), chemical stability, as well as irreversible reduction or oxidation of certain contaminants in water.
“Engineered graphene (G) and graphene (GO) have shown significant potential for ultrathin and ultrafast separations of gas molecules (Jiang and al., 2015). The intrinsic anti-microbial properties of graphene-based carbon materials are a further indication of their potential for water treatment membranes with antimicrobial and fouling resistance properties (Perrault, Jiang, and Al., 2013). Flat GO membranes, which use GO without any matrix, have shown a 4-10x increase in water flux compared to commercial nanofiltration membranes. The present invention uses crumpled or particulate GOP. It is structurally three-dimensional in comparison to GO sheets and intrinsically porous within the polymer matrix. Crumpled GO structures can have physical defects such as vacancies or holes with high ridges or low valleys. These channels and pathways are capable of allowing for rapid water transport and permeation. Cross-linking crumpled GO with polysulfone or polyamide, or any other polymeric material used for membrane fabrication gives rise to hydrophilic properties. This is due to the high number of hydrophilic functional group such as hydroxyl and carboxyl (?OH) and?COOH. The GO-polymer membranes are less than 10 nm in effective pore size. This makes them suitable for removing colloidal, biological, macro-molecular organics and ions through a combination?size, exclusion and depth filtration. These membranes are suitable for many applications, including water treatment, wastewater treatment and industrial separations. The modification of hydrophilic group such as the sulfuric groups will allow for fine tuning of membrane properties like pore-size and molecular weight cutoff, hydration ability, fouling resistance, and aqueous transport speeds.
Reverse osmosis (and nanofiltration membranes) are the main processes used for water applications, including water reclamation and desalination. These membranes usually contain an active polymer and an ultrathin (0.2?m), but high-cross-linked layer. This layer is dense, amorphous, and has very small interstitial gaps (?0.5nm) (Kong and al., New Journal of Chemistry 34, 2101-2104 2010, 2010; Maruf and al. Journal of Membrane Science 405-406, 175, 2012). Most reverse osmosis membranes contain either cellulose (CA) and aromatic polyamides. Desalination has been a major application of the older CA membranes. CA membranes can only be used in desalination at pH 4.5-7.9. They are susceptible to biological fouling and easily compact at high pressures. PA membranes, on the other hand, are more compatible with higher temperatures and a wider pH range. They are also more resistant to pressure compaction and biological attack. The thin, but effective sieving layer on the PA membranes makes them highly water-permeabile and salt-rejecting. The PA membranes can be damaged by the addition of hypochlorous acid to municipal water to prevent biological fouling and exposure to low or high pH conditions. Other limitations include the inability to make polymers with uniform and manageable pore sizes below 1 nm. This is due to a lack of suitable building blocks and/or methods to control pore architecture in this small-sized regime. The control of pore size is critical to finding the optimal balance between high water permeability, effective molecular and ionic rejection, and low water permeability. The primary membranes used for water desalination are thin-film composite (TFC), reverse osmosis membranes. These membranes typically consist of two layers: one dense layer and one porous sub-layer (Matsuura and Synthetic Membranes, Membranes Separation processes). CRC press, Boca Raton, Fla., 1994). It is typically an aromatic polyamide PA that forms the dense layer. This is what does the actual desalination. It is made on a porous layer of polysulfone which provides mechanical support and reduces pressure drop. (Fritzmann, Desalination. 216 (1): 1-76, 2007). These membranes usually have an ultrathin, but high-density amorphous polymer layer. They also have very small interstitial gaps (?0.5 nm). Because they can be used as high flux molecular sieving membranes, such as those made of zeolite nanocrystals and carbon nanotubes, nanostructured materials, including nano-objects like zeolite nanocrystals, have attracted attention (Li et.al., Journal of Membrane Science 243 (1) 401-404, 2004; Li. et.al., Water Research 42, 4923-4928 2008). They are not perfect for salt rejection due to their residual ionpermeability around the zeolite crystals. CNT pores are too small to be used as molecular sieves to exclude small ions. Graphene is also worth attention for its unique properties. It consists of a single, hexagonally arranged sp2-hybrized-carbon atoms. It is cheap and has excellent mechanical characteristics (Holt et.al., Science 312, 1034-1037; Fornasiero et.al. Proceedings of the National Academy of Sciences 105(45), 17250-17255 2008; Booth et.al., 2008, 2008, Li et.al., Journal of Macromolecular Science Part A Pure and 111 a Polymer Science, 0243060946, 2009, Rajbartoreh et14306, 014306-01430611, 109 (1), 113061306130006 a 2011 These properties indicate graphene’s potential to make thin, high-flux membranes. However, graphene is inert to molecules as small and small as helium, so it is necessary to create sub-nano pores that allow water to pass through the membrane. (Nair et.al., Science 335 (6067), 442-444 (2012)
Recent simulations and experiments suggest that sub-nanometer pores may be controlled using methods like oxidation, electron beam radiation, or deposing. Theoretical studies have been done on water transport and the rejection of graphene sheets by ions. Molecular dynamics simulations have been used to study the transport of water and ions through graphene pores at?0.5 nm and CNTs. Graphene is highly hydrophobic, so it should be expected that graphene will cause major membrane fouling (Wang and al., Langmuir 25(18), 11078-11811, 2009).
“Graphene oxide (GO) is a partially oxidized, hydrophilic, form of graphene. It has been found to increase water flux (details are below). However, GO can be leached from membranes over long periods of times because it is partially hydrophilic (Hu and Mi in ACS Nano, 4(7): 4317-4323; Perreault et. al., Environmental Science and Technology Letters 1(1): 71-76, 2013, 2013). Studies have also shown that GO’s pores are of the order 1 nm, which makes it less suitable for reverse osmosis. However, it is capable of acting as a nano-level filtration layer. It was used as a membrane coating to enhance antifouling properties but had a limited impact on water flux (Choi et.al., ACS Applied Materials and Interfaces 5(23), 12510-1219, 2013; Perreault et.al., 2013).
“Most polymeric materials are good at chemical, mechanical and thermal properties. However, they can be more hydrophobic than desired. Their susceptibility for membrane fouling makes them unsuitable for long-term water-based separations. There are many ways to make these membrane surfaces more hydrophilic, including polymer grafting and polymer mixing, ion beam radiation and plasma treatment. Polysulfone membranes have a wide range of applications in the medical, pharmaceutical, sterilization, and environmental industries. They are known for their high mechanical toughness, higher hydrophilic character and chemical inertness (pH & oxidation tolerance), low costs, and long durability (Kull and colleagues, Journal of Membrane Science 246, 203-215 2005). Polymer structure modifications such as those described above can result in membranes that have higher permeate fluxes and lower trans-membrane pressures. They also offer greater fouling resistance. This would improve the economic and technological value of long-term applications as well as their efficiency. Combining nanomaterial infusion and polymer formulation seems to be a promising method for improving membranes.
“As mentioned above, the idea of a single polymer that can perform multiple functions in water purification membranes is challenging. A number of properties are needed, including (a) minimal membrane fouling (b), high permeate flux (c), good separation (rejection), characteristics, (d), excellent or acceptable mechanical property and (e) long endurance. These properties cannot be found in one polymer. It is impossible. Multiple research groups have shown that chemical modification of the bulk or surface of the membrane is possible. Surface treatment has been used to modify ultrafiltration, nanofiltration and reverse-osmosis membranes. Modification of the membrane, however, seems to be very limited. The bulk material. These embodiments are intended for this purpose. The first (A), aims to modify commercially available membrane polymers, particularly polysulfones, and aromatic polyamides, as illustrated in FIG. 3. Modifications can be made at the membrane surface, or in bulk material. The second approach (B) proposes a polymer composition that includes a polymer substrate and nano objects (NOs), in the following forms: (1) graphene derivatives like graphene oxides (GO) or (2) Zeolite nanocrystalss (ZNCs).
“A water permeable membrane is provided in at least one embodiment for water purifications applications, including ultrafiltration, nanofiltration, and/or reverse-osmosis. The water permeable membrane comprises a porous support, and a composite layer that is disposed over it. The composite layer contains graphene oxide, which is dispersed in a polymer matrix.
“A water purification system is also provided in another embodiment. It includes the water permeable membrane described above. The water purification system comprises a chamber with a first water hold section to store impure water and second water hold section to hold purified water. Between the first and second water holding sections is a water permeable layer. A pressure applicator is included in the water purification system. This applies pressure to impure the first section of water holding. Water permeates through this membrane and into the second section.
“As necessary, detailed embodiments for the present invention have been disclosed. However, it is to understand that these embodiments are only exemplary and that other forms of the invention may also be possible. Figures are not necessarily scaled; certain features may be magnified or reduced to highlight particular components. Specific structural and functional details herein should not be taken as restrictive, but rather as a basis for teaching others how to use the invention in various ways.
“All numerical quantities in this description that indicate amounts of material, conditions of reaction, or use must be taken as modified by the expression ‘about’. when describing the invention’s broadest scope. It is preferable to practice within the stated numerical limits. Except where stated otherwise, percent (%), is referred to as?parts from? The ratio values and weights are determined by the weight of the material; the term “polymer” is used. Includes?oligomer? ?copolymer,? ?terpolymer,? ?terpolymer,?
It is important to understand that the invention is not limited by the particular embodiments and methods listed below. Specific components and/or conditions could, however, differ. The terminology used in this document is intended only to describe particular embodiments. It is not meant to be restrictive.
“It is important to note that the singular forms?a? and?an? as well as?the are plural. Unless the context indicates otherwise, plural referents will be used. Referring to a single component is an example of a plural referent.
“Where publications are referenced in this application, the disclosures from these publications are hereby incorporated into this application by reference in their entirety to better describe the state-of-the art to which this invention applies.”
“ABBREVIATIONS”
“?AHS? “?AHS?” means aquatic humic substances.
“?BOD? means biochemical oxygen demand;”
“?CA? means cellulose acetate;”
“?CE? means cellulose esters;”
“?CN? means nitrocellulose;”
“?CNT? means carbon nanotube;”
“?COD? means chemical oxygen demand;”
“?CSA? “?CSA” means camphor sulfonic acids;
“?DI? “?DI?” means distilled water.
“?DMF? means N,N-Dimethylformamide;”
“?DOC? “DOC” means dissolved organic carbon.
“?EDC? means endocrine disrupting chemicals;”
“?EDS? “?EDS?” means X-ray dispersion spectrumcopy;
“?EPS? “?EPS?” means exopolymeric substances.
“?G? “?G??” means graphene.
“?GO? means graphene oxide;”
“?HOB? “?HOB?” means hydrophobic bases.
“?HON? means hydrophobic neutrals;”
“?HIA? “?HIA?” means hydrophilic acid;
“?HIB? “?HIB?” means hydrophilic bases.
“?MBR? means membrane bioreactor;”
“?MCL? means maximum contaminant levels;”
“?MD? means molecular dynamics;”
“?MPD? means m-phenylene diamine;”
“?MWCO? “?MWCO?” means molecular weight cutoff;
“?NO? means nano-object;”
“?P(BASS-S-CMS)? means poly (tetrabutyl ammonium styrene sulfonate-co-styrene-co-4-chloromethyl styrene);”
“?PA? means polyamide;”
“?PAC? “?PAC?” means powder activated carbon;
“?PAN? means polyacrylonitrile;”
“?PDA? means phenylene diamine;”
“?PES? “?PES?” means polyethersulfone.
“?PP? means polypropylene;”
“?PPCP? “?PPCP?” means personal care product.
“?PS? means polysulfone;”
“?PSSA? “?PSSA” means polystyrene-sulfonic acid.
“?PTFE? means polytetra-fluoro-ethylene;”
“?PVC? means polyvinyl chloride;”
“?PVDF? means polyvinylidene fluoride;”
“?r-GO? “?r-GO?” means reduced graphene dioxide;
“?RO? means reverse osmosis;”
“?SEM? “?SEM?” means scanning electron microscopy.
“?TEA? “?TEA?” means triethanolamine;
“?TEM? means transmission electron microscopy;”
“?TFC? “?TFC?” means thin-film composite.
“?TMC? means trimesoylchloride;”
“?TOC? “?TOC?” means total organic carbon.
“?UF? “?UF?” means ultrafiltration.
“?ZNC? means nanocrystals.”
“Refer to FIG. “With reference to FIG. 1, a schematic illustration is provided of a water permeable water membrane for water purification system. Water permeable membrane 10 comprises porous support 12, and a composite layer 14, which is disposed on top of the porous support. Composite layer 14 contains graphene oxide, which is dispersed in a polymer matrix. Composite layer 14 has a thickness of approximately 10 nm. Some variations of composite layer 14’s thickness are greater than others in increasing order, such as 5 nm or 10 nm. 50, nm and 100 nm. 50 nm. Other variations of composite layer 14 have a thickness that is lower than in increasing order. These include 1 mm or 0.1 mm. 1000, 500, nm and 200 nm. Porous support 12 can also include an optional fabric layer 18, which is typically disposed over the polymeric layer 16.
“With reference to FIG. “With reference to FIG. 2, a schematic illustration is provided of a water purification device using the water permeable material set forth above. This water purification system works in reverse osmosis. Water purification system 20 comprises chamber 22. It has a first water storage section 24 that holds impure water, and a second water storage section 26 that holds purified water. The water permeable membrane 10, which is water, is placed between the first and second water holding sections 24 and 26. Water purification system 20 can also include a pressure applicator 28, which is a pump that applies pressure to impurify water in the first section 24. This allows water to permeate through the water permeable membrane 10 and into the second section 26. The pressure regulator 30 maintains the water holding section 24 at a constant level. Through inlet 32, impure water can be introduced to water purifications systems 20 during operation. Under pressure, the water enters first section 24 through pressure applicator 30, One refinement shows that first water holding section 24 can be operated at pressures ranging from 20 to 1500 PSI. Another refinement calls for first water holding section 24 to be operated at a pressure of between 30 and 250 psi. Another refinement is that first water holding section 24 can be operated at 600 to 1200 PSI. Water moves across a water permeable membrane 10 when it is held at a higher pressure. Water section 10 contains water that is purer than the original water. Purified water exits via outlet 34, while water with concentrated impurities exits via outlet 36.”
“The water permeable membrane according to the invention of the present invention, includes graphene dioxide and graphene nanostructures. While the exact structure is not known, it seems to contain sections of graphene that have been?oxidized?. Areas that are water-permeable indicate a chemical modification to graphene. The graphene oxide nanostructures can be varied in size and shape. The thickness of the membrane is not limiting. It can be as thin as a few nanometers to several microns or even several millimeters.
“Graphene oxide” is partially oxidized graphene with carboxyl,hydroxyl and epoxide functional group that makes it water-soluble. The graphene dioxide is a reduced grapheneoxide. GO’s nano-sized structures will typically have a spatial dimension of less than a micron. Other refinements may result in nano-sized structures having a smaller spatial dimension than 500 nm or 100 nm. Or on the order of several nanometers. Other refinements may have a larger spatial dimension than 3 angstroms or more than 5 angstroms. Another refinement shows that graphene oxide can have a spatial dimension of 10 nn to 500 nm. The graphene dioxide is typically present in an amount of between 0.05 and 20 weight percent of total weight of grapheneoxide and polymer matrix. Some refinements may result in graphene dioxide being present in an amount higher than 0.01 weight percent. 0.05 weight percentage, 1.0 weight%, 2.0 weight%, or three weight percent of the total weight of the grapheneoxide and polymer matrix. Some refinements may have the graphene dioxide present in a lower amount than 50, 30, 40, 20, 20 and 10 weight percent respectively.
“The water permeable membrane according to the invention comprises a polymer matrix in which graphene oxide is dispersed. Examples of suitable polymeric matrixes include, but are not limited to, cellulose acetate, nitrocellulose, and cellulose esters (CA, CN, and CE), polytetra-fluoro-ethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyacrylonitrile (PAN), polyamides, polyimides, polyvinyl chloride (PVC), polysulfone (PS), polyether sulfone (PES) polyether sulfone (PES), polyethylene and polypropylene (PE and PP). This is especially true for polyamide and a cross-linked matrix of polyamide. Polyamide can be sulfonated or not. The polyamide can be an aromatic polyamide with C6-12 aromatic groups. Another useful polymer matrix is a sulfonated or non-sulfonated poly (tetrabutyl ammonium styrene sulfonate-co-styrene-co-4-chloromethyl styrene)-polyvinylidene fluoride blend.”
“A. “A.
“Materials that include polymers with different molecular masses and distributions, as well as degree of branching, can be synthesized and characterized using solid and solution state characterization methods. Changes in polymer polarity induced by systematic changes in polymer composition may be carried out by copolymerization and/or chemical-functionalization. Copolymerization has many advantages, including the ability to produce consistent chemical compositions. These examples have been shown above. The most promising for performance are aromatic polyamides. There are several possible routes, including: (a) Chain topology, i.e. Increases in chain branching through the addition of branching unit in the diamine For instance, small variable fractions of 1,3,5-triaminobenzene may be added in order to increase segments densities. (b) A second and promising approach is chemical modification of the polyamide (PA) through chemical modification of the polyamide backbone through changes in the copolymerization of trimesoyl chloride with 2,4-diamino-N,N-dimethylaniline, 1, along with 1,3-phenylenediamine (PDA) (also known as m-phenylenediamine or MPD) as illustrated in FIG. 3. The chemical structure can be further modified by the transformation of 1 into copolymers 3, and 4, where 3 has a anionic character, while 4 is a neutral copolymer with a zwitterionic secondary ammonium sulfurate copolymer (FIG. 3). These structures are those of a copolymer in which the molar ratio [phenylene dimamine]/[1] equals 2. You can easily adjust the ratio to alter the ionic characteristics and degree of functionalization. It should be kept to a minimum as too much ionic functionalization could lead to a decrease in salt rejection, organic rejection, or filtration selectivity.
“B. Polyamide-Nanomaterial Composites.”
“The addition nano-objects into the polymer matrixes will affect the surface and bulk properties. This can be controlled through modular membrane synthesis protocols. The dramatic effects of adding GO to water flow are evident in the following studies. It is possible to synthesize GO from graphene (Suk et. al. ACS Nano, 4(1), 6557-6564 2010, 2010; Zhu et. al. Advanced Materials 22 (35) 3906-3924 2011, 2011). This will allow for greater control over reproducibility and the effects oxidation conditions have on chemical structure. Further chemical functionalization will be possible (see below).
“Various embodiments may include the incorporation of hydrophilicNOs to an aromatic polyamide matrix (PA) (FIG. 4) by interfacial polymerization (MPD, trimesoyl chlorineide (TMC), precursors with MPD containing different amounts of NOs. These nanocomposites can be functionalized with carbon-based nanomaterials like CNTs or GOs. Two-dimensional capillaries made of closely spaced graphene sheets have been suggested to allow water to flow with low friction (Nair and al., 2012). Suk et. al. (2010) also found that GO has strong chemical and mechanical stability. GO has antibacterial properties which would reduce the microbial attack of membranes (Hu et. al., ACS Nano 4(7), 4317-4323 in 2010; Liu et. al., ACS Nano 5(9), 6971?6980 in 2011). The GO particles may be added to various phenylene diamines in variable quantities so that the scalability as reverse osmosis/nanofiltration membrane material and the effects on aqueous flow properties can be evaluated. This allows membrane selectivity to be maintained while optimizing water flux and antifouling properties. This can be done with any of the four main polymer matrix types: (a) neutral PA; (b) PA copolymer modified using varying fractions quaternary ammonium haides; (c) PA functionalized by sulfonated zwitterions and (d) partially-sulfonated anions PA (FIG). 5).”
“This chemical modification of copolymers 3 & 4 can be compared to the sulfonic Acid copolymer product, 5 Both cases show that the hydrophilicities are controlled by the PAs.
“Functionalization Of Graphene Oxide.”
To reduce biological fouling, a surface functionalization using nano-objects (NOs), could be performed. This could include the carbodiimide-mediated functionalization carboxylic groups into anamide that carries at least a tertiary amino (FIG). 6). This will then be alkylated to produce a Tertiary Ammonium Halide (structures unknown) and the introduction a Zwitterionic Ammonium Sulfonate by reaction of an amine with a sulfurone (FIG. 6). The first case introduces a cationic charged, while the second is electrostatically neutral. These changes will allow us to better understand the issue and help to define its scope. These variations can all be tracked and evaluated through intra-campus collaboration between members of both research teams.
“Membrane Characterization.”
“Surface characterization can be done using scanning electron microscopy and transmission electron microscopy. Monitoring changes in the surface energies can help determine the structural and physicochemical impacts on the surface, for example by atomic force microscopy, surface energies and altered morphologies of inner (bulk), membranes. These are then studied using transmission and surface electron microscopes (SEM/TEM respectively). Materials made up of polymers with different molecular masses and distributions, as well as branching degrees, can be synthesized and characterized using both solid-state and solution characterization methods (see below). Changes in membrane hydrophobicity induced by systematical changes in polymer compositions may be carried out by copolymerization or end-functionalization that has potential for considerable structural control. Nano-objects can be added to polymer matrices. This will have an impact on the surface and bulk properties. Modular membrane synthesis will allow for considerable control. This will also affect the pore sizes and shapes.
“Membrane Fouling Control & Cleaning Strategies”
“In the contexts of membrane synthesis, development, and membrane fouling in integrated processes are important. These factors include colloids, extracellular polymers, inorganic precipitates, scalants and biomass. They are affected by process operating conditions. These factors are responsible for membrane fouling in these systems: (i. macromolecular and collloid sorption; (ii. biofilm growth and attachment); and (iii. inorganic precipitation and scaling. (Tsai and Pirbazari in Journal of Environmental Engineering and Science 3(6), 507-521 in 2004; Williams and Pirbazari in Water Research 41 (17), 3880-3893, 2007; Ravindran and colleagues in Journal of Membrane Science. 344(1-2), 39-54, 2009). Fouling can be caused by the absorption of hydrophobic substances onto and within membrane pores and the deposition of a cake or gel layer on membrane surface. Extracellular polymeric substances (EPS), which mainly contain carbohydrates, proteins and nucleic acid, are the main causes of biological fouling (Williams et al. 2007; Ravindran, et al. 2009). Powder activated carbon (PAC), an adsorbent, and fluid management can reduce permeate flux and prevent membrane fouling (Williams, Pirbazari and Ravindran, 2009; Williams and et. al. Chemical Engineering Science, 84,511, 2012). The PAC removes dissolved biological and other matter from the water and re-entrains colloids, suspended solids and liquids from the viscous layer. It absorbs all organic and bio-organic pollutants in wastewaters and reclaimed water, including proteins, carbohydrates, and fats (Kilduff andWeber, Environmental Science and Technology 26 (3), 569-577 1992). PAC reduces the thicknesses of hydrodynamic and mass-transfer boundary layers, lowers concentration polarization and controls gel deposition on membrane surface or pores (Pirbazari et. al. Water Research, 30(11), 2691-2706, 1996; Tsai et. al. Journal of Environmental Engineering and Science 3(6), 507-521 2004, Ravindran et. al. 2009).
Concentration polarization suppression, optimization of chemical and physical cleaning protocols and pre-treatment of feed can all be used to control membrane fouling (Tu et.al., Journal of Membrane Science 265 (1-2), 29-50; Williams and Pirbazari 2007, 2007). For flux recovery and maintenance of rejection, fouling control, flux recovery and rejection maintenance are all important aspects of membrane cleaning strategies. For removing hydrophobic substances and other major contributors to organic, biological, or organic fouling, the efficacy of different cleaning agents, such as acids, surfactants and enzymes, may be evaluated. It may also be possible to determine the chemical tolerance of these cleaning agents.
“The synthesis of new RO membranes can be achieved using the materials described in this document. They have enhanced water flux, improved resistance to organic, biochemical fouling, scaling, and other degradation processes.”
“Graphene oxide, a nano-sized material that is synthesized through controlled oxidation graphite, can be found in a variety of commercially affordable materials. GO, a nano-sized structure, will typically have a size range of less than 0.1 micron. Other refinements may result in nano-sized structures having sizes ranges less than 500 nm or 100 nm. Or on the order of several nanometers. Other refinements may allow for sizes that are greater than 3 angstroms or 5 angstroms. Partially oxidized graphene (GO) contains carboxyl, hydrol, and/or epoxide functional group that make it water-soluble. GO can also be dissolved in organic solvents. It is well-known for its strong chemical and mechanical stability (Suk et.al., ACS Nano 2010, 4(11), 6557-66564; Dmitriy et.al. Nature 2007, 448-457-460). GO also has antibacterial properties (Liu et al., ACS Nano, 2011, 5(9), 6971-6980; Hu et al., ACS Nano, 2010, 4(7), 4317-4323). When GO is used as an active layer, or mixed with a polysulfone membrane (PS), it has been shown that it can only be used as a microfiltration and nanofiltration membrane because there are no blocking monovalent ions. Sci. Sci.
“Embodiments described herein incorporate GO in aromatic PA matrices via interfacial Polymerization of trimesoyl chloride and phenylene diamines (PDA), which both contain varying amounts of Go’s. The high salt rejection of PA membranes means that they can also be used as ultrafiltration membranes (UF). The incorporation of GO to PA could promote UF or desalination processes. This is done by putting GO’s onto the PA surface in the final stages of polymerization, or in the bulk through the dissolution of GO?s into the PDA solution.
“Initial work consisted of the development of polymer-synthesis protocols that included appropriate reaction schemes, free radical processes, syntheses conditions like reaction times, curing methods, and quantitatively controlled infusion of graphene oxide. These conditions were modified to produce superior membranes. These membranes were prepared using interfacial polymerization with sequential addition of MPD, TMC on a commercially available polyether sulfone ultrafiltration membrane base. It has a nominal pore diameter of 0.08 microns and a molecular weight cutoff (MWCO), of 10,000 Daltons. This ultrafiltration membrane is the most effective commercially available for water reclamation and other related applications. Monomers used to prepare polyamide membranes were m-phenylene dimamine (MPD), 1,3,5-benzene trimesoyl chloride (TMC) and 1,3,5 benzene tricarbonyl chloride (TMC). These monomers MPD, TMC were used to create another set of membranes. However, camphor sulfonic (CSA) was added to the mix to increase the solvophilicity of the membranes and observe their rejection, aqueous transport, and hydrophilicity.
Summary for “High-performance membranes for water reclamation with polymeric and nanomaterials.”
“Conventional separations process recover, isolate and purify products from virtually all manufacturing spheres. This includes chemicals, pharmaceuticals and petroleum as well as electronics, automobiles, and aerospace. These processes are energy-intensive and costly and account for between 40 and 70 percent of capital and operational costs. They also account for 45 percent to 45 percent of the energy costs in the petroleum and chemical industries, excluding any pollution control costs. Industries have been shifting their attention from treatment and pollution to water recovery, reuse, and recycling in recent years. This is mainly due to severe water shortages and droughts as well as stricter environmental regulations, rising treatment cost, and spatial constraints. Membrane technology offers a viable, more efficient alternative to traditional separations that also has significant economic and environmental benefits. Due to their many applications in commercial, industrial, and environmental settings, processes such as reverse osmosis, microfiltration, ultrafiltration and nanofiltration have received significant attention.
“Membrane technologies have to overcome many technological hurdles before widespread implementation. These include membrane fouling and permeate flux decline. They also need to be able to separate (reject) well and are not durable. These issues require innovations and development in membrane production that is more resistant to fouling, has higher permeate flux, and displays better selectivity.
“Semipermeable RO membrane mediated processes are one of the most efficient methods to remove salts (Na, monovalent and divalentions ions), and other aqueous contaminants. Because of their high salt rejection and pH tolerance, thin-film composite polyamide membranes (PA) dominate the market. These membranes have low water permeabilities due to their rigid, cross-linked structure. These membranes are also susceptible to temperature changes, low durability and sensitivity to microbial attack (biodegradation), as well as a lack of resistance against different types of fouling. Due to the high pressures needed for sustained and enhanced water flux, energy demands are high.
“The incorporation of nano-sized objects, such as carbon nanotubes or zeolites, into RO membranes has been attempted to improve their performance, but the results have been limited (Li L. et al. J. Membr. Sci., 2004, 243, 401-404; Li L et al., Desalination, 2008, 228, 217-225; Fornasiero F et al., Proc. Natl Acad. Sci. USA, 2008, 105, 17250-17255; Holt J K et al., Science, 2006, 312, 1034-1037).”
“There is a need to improve RO membrane structures and methods of making them.”
The infusion of nanoobjects (NOs), into polymeric matrixes to create nanocomposites is a promising frontier in membrane technology. This could lead to significant improvements in aqueous transport as well as fouling resistance. Examples include the use of carbon nanotubes (CNTs), which facilitate micro-transport of water. CNTs can be used to increase polymer hydrophilicities by incorporating polar functional groups. This reduces their potential for organic, inorganic, and particulate fouling. CNTs have antibacterial properties, which can significantly reduce biofilm formation and biological fouling. Their use can also lead to stronger membranes that are less susceptible to mechanical failures (Xie et. al., Materials Science and Engineering 49, 89-112, 2005). Infusion of nanomaterials in polymeric materials can lead to significant energy savings as well as lower operation and maintenance costs. Zeolite nanocrystals (ZNCs), for instance, have been shown to increase membrane hydrophilicity as well as aqueous non viscous micro-transport characteristics (Lind and al., Langmuir 25 (17), 10139-10145 2009). A combination of nanomaterials could have a synergistic effect on water transport.
“The embedded materials described herein target new types of polymeric and nanomaterial-based membranes for use in integrated membrane systems, such as the membrane bioreactor process (MBR), for water purification, groundwater recharge, and water reuse.
“Integrated systems like MBR have demonstrated excellent potential for water reclamation and reuse, groundwater replenishment, and other similar applications. The technology can be made more economical and efficient by using superior membranes that have better anti-fouling and aqueous transport. They can reduce operating costs by a significant amount, and even lower energy costs. Continuous flow hybrid MB R systems offer several technical advantages over traditional biological processes in environmental applications. They are small and footprint-friendly, require very long solids retention times and efficiently retain particulates, colloids and contaminants. To meet groundwater recharge requirements, the treated effluent must be low in suspended solids and chemical oxygen demand (COD), biochemical oxygen demand(BOD), total organic carbon, (TOC), and most pathogens. Modern, computerized and programmable control systems can make the MBR process more compact, efficient, and economically feasible. An adsorbent like powder activated carbon will be used to defoul membranes and maintain high permeate flows (Pirbazari and Pirbazari in Water Research, 30, 11), 2691-2706, 1996. Williams and Pirbazari in Water Research 41 (17), 3880-3893, 2007; Williams et.al., Chemical Engineering Science 84, 494-511 (2012). The adsorbent will also be able to remove trace levels or residual micro-pollutants, including those that disrupt hormones (EDCs), such as pesticides, pharmaceuticals, and solvents, during water reclamation (Snyder and al., Desalination), 202(1-3), 152-181, 2007).
“Nanofiltration is a widely-used technology in wastewater treatment and water reclamation. Ultrafiltration and microfiltration are used to pre-treat nanofiltration membranes against biological and organic fouling. However, nanofiltration membranes or reverse osmosis membranes can be prone to inorganic fouling and inorganic scaling. This is due to the deposition of inorganic precipitates such as calcium carbonate, magnesium sulfurate, and many others. The membrane must be capable to repel cations like calcium and magnesium ions, as well as anions like sulfates or carbonates. This will reduce the possibility of membrane scaling from precipitation. The present invention employs nanomaterial and membrane polymer formulations in some embodiments to reduce organic scaling. This is done by using surface charge mechanisms.
“Reduction of all inorganic fouling is an important consideration when preparing nanofiltration membranes or reverse osmosis membranes using polymer blends that include the infusion of nanomaterials. The rejection and organic fouling potential of nanofiltration membranes for wastewater treatment and water reclamation are determined by the molecular sizes and weights of organic constituents. Imai et. al. (2002) extensively discussed this topic. These six main components of dissolved organic matter are: (1) Aquatic Humic substances (AHS), (2) Hydrphobic bases [HOB], (3) Hydrophobic neutrals (?HON?), (4) Hydrophilic acid (HIA), five Hydrophilic basess (HIB), and six Hydrophilic neutrals (?HIN?). HON and HIN, while not acidic or basic, are neutral in nature. These aspects should be considered carefully from the perspective of organic fouling membranes, especially nanofiltration membranes that can best remove them.
“The most widely used polymeric membrane materials in conventional applications are the following: cellulose acetate, nitrocellulose, and cellulose esters (CA, CN, and CE), polytetra-fluoro-ethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyacrylonitrile (PAN), polyamides, polyimides, polyvinyl chloride (PVC), polysulfone (PS), polyether sulfone (PES) polyether sulfone (PES), polyethylene and polypropylene (PE and PP).”
“Several studies have been done to improve the hydrophilic properties of polymers, especially in the case PS and PES membranes. (Richards, et al. 2012). This has been done by: (1) mixing polymers such as PS with hydrophilic nanoparticles like SiO2, ZnO2, or TiO2; (2) grafting polymers such as PS and PES with more waterphilic or monomers; (3) coating the polymer in more hydrophilic materials. The advantages of blending polymers include excellent separation performance, chemical resistance, thermal resistance, pH tolerance and general adaptability to harsh environments such as wastewater treatment and water reclamation (Richards and al., 2012).
“An important aspect of membrane development is the consideration and application of new polymer formulations. For example, variations of this invention contemplate the use of polyvinylidene dimeride (PVDF), and polystyrene sulfuric acid (PSSA), with or without graphene, or graphene oxide. These copolymer and polymer blends are hydrophilic and hydrophobic functional groups. The latter is found on the outer surfaces. These types of polymer blends are used to achieve the desirable micro-structural and mechanical transportive, as well as fouling resistance properties of the polymer components. Use of polymer mixtures like those of PVDF or polystyrene sulfuric acid (PSSA), increases the mechanical strength, durability and robustness of the fabricated membranes. Variation in composition and blending will also allow for flexibility and tuneability of membrane pore sizes. This can enhance water molecules’ transport properties and reduce fouling potential. Fouling can be reduced on both the surface and inside of the membranes. Polymer formulations should improve the membrane’s mechanical strength, durability, longevity, chemical tolerance, pH tolerance, cleanability, and micro-structural integrity.
“In recent years, many nanoparticles were incorporated into membranes, such as those of metals, metal oxides, or non-metal oxygens, including SiO2, Al2O3, ZeO2, ZnO2, ZrO2, and Ag, as well as zeolites and single and multiwalled carbotubes (CNTs), for various purposes, including wastewater treatment. Richards et. al (2012) have reviewed these issues extensively. They can treat two types of fouling: organic fouling from natural organic matter and synthetic material, and biological fouling caused by microorganisms, including their exudates. These nanoparticles can also improve the aqueous transport properties. Li et al. (2006) found that the PES-TiO2 membrane’s water flux was significantly increased by the addition of titanium dioxide nanoparticles. However, the flux was dependent upon the concentration of nanoparticles. The researchers also found that nanoparticles are very volatile and can be easily agglomerated due to their high diffusivity. Because of their biocidal and bactericidal properties, these nanoparticles can be used to control biological fouling (Zodrow and Richards, 2009; Richards and Al, 2012). Maximous et al. Maximous et al. Bae and Tak (2005) found that titanium dioxide (TiO2) was not only attracted to the membrane’s surface, but also to the membrane pores. This led to decreased membrane permeability and higher filtration resistance. This is a significant factor in membrane synthesis. These studies revealed that metal and metal oxide nanoparticles were more attracted to water molecules than plain polymeric membranes. Therefore, their immunization in polymer matrixes was beneficial for water flux and fouling control. Use of carbon-based nanomaterials like graphene (G), CNTs (CNT), and grapheneoxide (GO) may have a greater impact on the performance of polymeric membranes in terms of aqueous transportation and fouling control. Because of the inherent characteristics of GO, it is expected to have a greater impact on impregnation polymeric matrices. Use of nanomaterials like G or GO in polymer formulations at different concentrations is intended to promote ant-friction microflow water transport, biocidal characteristics (regarding the resistance to biological fouling, destruction of pathogenic organisms), chemical stability, as well as irreversible reduction or oxidation of certain contaminants in water.
“Engineered graphene (G) and graphene (GO) have shown significant potential for ultrathin and ultrafast separations of gas molecules (Jiang and al., 2015). The intrinsic anti-microbial properties of graphene-based carbon materials are a further indication of their potential for water treatment membranes with antimicrobial and fouling resistance properties (Perrault, Jiang, and Al., 2013). Flat GO membranes, which use GO without any matrix, have shown a 4-10x increase in water flux compared to commercial nanofiltration membranes. The present invention uses crumpled or particulate GOP. It is structurally three-dimensional in comparison to GO sheets and intrinsically porous within the polymer matrix. Crumpled GO structures can have physical defects such as vacancies or holes with high ridges or low valleys. These channels and pathways are capable of allowing for rapid water transport and permeation. Cross-linking crumpled GO with polysulfone or polyamide, or any other polymeric material used for membrane fabrication gives rise to hydrophilic properties. This is due to the high number of hydrophilic functional group such as hydroxyl and carboxyl (?OH) and?COOH. The GO-polymer membranes are less than 10 nm in effective pore size. This makes them suitable for removing colloidal, biological, macro-molecular organics and ions through a combination?size, exclusion and depth filtration. These membranes are suitable for many applications, including water treatment, wastewater treatment and industrial separations. The modification of hydrophilic group such as the sulfuric groups will allow for fine tuning of membrane properties like pore-size and molecular weight cutoff, hydration ability, fouling resistance, and aqueous transport speeds.
Reverse osmosis (and nanofiltration membranes) are the main processes used for water applications, including water reclamation and desalination. These membranes usually contain an active polymer and an ultrathin (0.2?m), but high-cross-linked layer. This layer is dense, amorphous, and has very small interstitial gaps (?0.5nm) (Kong and al., New Journal of Chemistry 34, 2101-2104 2010, 2010; Maruf and al. Journal of Membrane Science 405-406, 175, 2012). Most reverse osmosis membranes contain either cellulose (CA) and aromatic polyamides. Desalination has been a major application of the older CA membranes. CA membranes can only be used in desalination at pH 4.5-7.9. They are susceptible to biological fouling and easily compact at high pressures. PA membranes, on the other hand, are more compatible with higher temperatures and a wider pH range. They are also more resistant to pressure compaction and biological attack. The thin, but effective sieving layer on the PA membranes makes them highly water-permeabile and salt-rejecting. The PA membranes can be damaged by the addition of hypochlorous acid to municipal water to prevent biological fouling and exposure to low or high pH conditions. Other limitations include the inability to make polymers with uniform and manageable pore sizes below 1 nm. This is due to a lack of suitable building blocks and/or methods to control pore architecture in this small-sized regime. The control of pore size is critical to finding the optimal balance between high water permeability, effective molecular and ionic rejection, and low water permeability. The primary membranes used for water desalination are thin-film composite (TFC), reverse osmosis membranes. These membranes typically consist of two layers: one dense layer and one porous sub-layer (Matsuura and Synthetic Membranes, Membranes Separation processes). CRC press, Boca Raton, Fla., 1994). It is typically an aromatic polyamide PA that forms the dense layer. This is what does the actual desalination. It is made on a porous layer of polysulfone which provides mechanical support and reduces pressure drop. (Fritzmann, Desalination. 216 (1): 1-76, 2007). These membranes usually have an ultrathin, but high-density amorphous polymer layer. They also have very small interstitial gaps (?0.5 nm). Because they can be used as high flux molecular sieving membranes, such as those made of zeolite nanocrystals and carbon nanotubes, nanostructured materials, including nano-objects like zeolite nanocrystals, have attracted attention (Li et.al., Journal of Membrane Science 243 (1) 401-404, 2004; Li. et.al., Water Research 42, 4923-4928 2008). They are not perfect for salt rejection due to their residual ionpermeability around the zeolite crystals. CNT pores are too small to be used as molecular sieves to exclude small ions. Graphene is also worth attention for its unique properties. It consists of a single, hexagonally arranged sp2-hybrized-carbon atoms. It is cheap and has excellent mechanical characteristics (Holt et.al., Science 312, 1034-1037; Fornasiero et.al. Proceedings of the National Academy of Sciences 105(45), 17250-17255 2008; Booth et.al., 2008, 2008, Li et.al., Journal of Macromolecular Science Part A Pure and 111 a Polymer Science, 0243060946, 2009, Rajbartoreh et14306, 014306-01430611, 109 (1), 113061306130006 a 2011 These properties indicate graphene’s potential to make thin, high-flux membranes. However, graphene is inert to molecules as small and small as helium, so it is necessary to create sub-nano pores that allow water to pass through the membrane. (Nair et.al., Science 335 (6067), 442-444 (2012)
Recent simulations and experiments suggest that sub-nanometer pores may be controlled using methods like oxidation, electron beam radiation, or deposing. Theoretical studies have been done on water transport and the rejection of graphene sheets by ions. Molecular dynamics simulations have been used to study the transport of water and ions through graphene pores at?0.5 nm and CNTs. Graphene is highly hydrophobic, so it should be expected that graphene will cause major membrane fouling (Wang and al., Langmuir 25(18), 11078-11811, 2009).
“Graphene oxide (GO) is a partially oxidized, hydrophilic, form of graphene. It has been found to increase water flux (details are below). However, GO can be leached from membranes over long periods of times because it is partially hydrophilic (Hu and Mi in ACS Nano, 4(7): 4317-4323; Perreault et. al., Environmental Science and Technology Letters 1(1): 71-76, 2013, 2013). Studies have also shown that GO’s pores are of the order 1 nm, which makes it less suitable for reverse osmosis. However, it is capable of acting as a nano-level filtration layer. It was used as a membrane coating to enhance antifouling properties but had a limited impact on water flux (Choi et.al., ACS Applied Materials and Interfaces 5(23), 12510-1219, 2013; Perreault et.al., 2013).
“Most polymeric materials are good at chemical, mechanical and thermal properties. However, they can be more hydrophobic than desired. Their susceptibility for membrane fouling makes them unsuitable for long-term water-based separations. There are many ways to make these membrane surfaces more hydrophilic, including polymer grafting and polymer mixing, ion beam radiation and plasma treatment. Polysulfone membranes have a wide range of applications in the medical, pharmaceutical, sterilization, and environmental industries. They are known for their high mechanical toughness, higher hydrophilic character and chemical inertness (pH & oxidation tolerance), low costs, and long durability (Kull and colleagues, Journal of Membrane Science 246, 203-215 2005). Polymer structure modifications such as those described above can result in membranes that have higher permeate fluxes and lower trans-membrane pressures. They also offer greater fouling resistance. This would improve the economic and technological value of long-term applications as well as their efficiency. Combining nanomaterial infusion and polymer formulation seems to be a promising method for improving membranes.
“As mentioned above, the idea of a single polymer that can perform multiple functions in water purification membranes is challenging. A number of properties are needed, including (a) minimal membrane fouling (b), high permeate flux (c), good separation (rejection), characteristics, (d), excellent or acceptable mechanical property and (e) long endurance. These properties cannot be found in one polymer. It is impossible. Multiple research groups have shown that chemical modification of the bulk or surface of the membrane is possible. Surface treatment has been used to modify ultrafiltration, nanofiltration and reverse-osmosis membranes. Modification of the membrane, however, seems to be very limited. The bulk material. These embodiments are intended for this purpose. The first (A), aims to modify commercially available membrane polymers, particularly polysulfones, and aromatic polyamides, as illustrated in FIG. 3. Modifications can be made at the membrane surface, or in bulk material. The second approach (B) proposes a polymer composition that includes a polymer substrate and nano objects (NOs), in the following forms: (1) graphene derivatives like graphene oxides (GO) or (2) Zeolite nanocrystalss (ZNCs).
“A water permeable membrane is provided in at least one embodiment for water purifications applications, including ultrafiltration, nanofiltration, and/or reverse-osmosis. The water permeable membrane comprises a porous support, and a composite layer that is disposed over it. The composite layer contains graphene oxide, which is dispersed in a polymer matrix.
“A water purification system is also provided in another embodiment. It includes the water permeable membrane described above. The water purification system comprises a chamber with a first water hold section to store impure water and second water hold section to hold purified water. Between the first and second water holding sections is a water permeable layer. A pressure applicator is included in the water purification system. This applies pressure to impure the first section of water holding. Water permeates through this membrane and into the second section.
“As necessary, detailed embodiments for the present invention have been disclosed. However, it is to understand that these embodiments are only exemplary and that other forms of the invention may also be possible. Figures are not necessarily scaled; certain features may be magnified or reduced to highlight particular components. Specific structural and functional details herein should not be taken as restrictive, but rather as a basis for teaching others how to use the invention in various ways.
“All numerical quantities in this description that indicate amounts of material, conditions of reaction, or use must be taken as modified by the expression ‘about’. when describing the invention’s broadest scope. It is preferable to practice within the stated numerical limits. Except where stated otherwise, percent (%), is referred to as?parts from? The ratio values and weights are determined by the weight of the material; the term “polymer” is used. Includes?oligomer? ?copolymer,? ?terpolymer,? ?terpolymer,?
It is important to understand that the invention is not limited by the particular embodiments and methods listed below. Specific components and/or conditions could, however, differ. The terminology used in this document is intended only to describe particular embodiments. It is not meant to be restrictive.
“It is important to note that the singular forms?a? and?an? as well as?the are plural. Unless the context indicates otherwise, plural referents will be used. Referring to a single component is an example of a plural referent.
“Where publications are referenced in this application, the disclosures from these publications are hereby incorporated into this application by reference in their entirety to better describe the state-of-the art to which this invention applies.”
“ABBREVIATIONS”
“?AHS? “?AHS?” means aquatic humic substances.
“?BOD? means biochemical oxygen demand;”
“?CA? means cellulose acetate;”
“?CE? means cellulose esters;”
“?CN? means nitrocellulose;”
“?CNT? means carbon nanotube;”
“?COD? means chemical oxygen demand;”
“?CSA? “?CSA” means camphor sulfonic acids;
“?DI? “?DI?” means distilled water.
“?DMF? means N,N-Dimethylformamide;”
“?DOC? “DOC” means dissolved organic carbon.
“?EDC? means endocrine disrupting chemicals;”
“?EDS? “?EDS?” means X-ray dispersion spectrumcopy;
“?EPS? “?EPS?” means exopolymeric substances.
“?G? “?G??” means graphene.
“?GO? means graphene oxide;”
“?HOB? “?HOB?” means hydrophobic bases.
“?HON? means hydrophobic neutrals;”
“?HIA? “?HIA?” means hydrophilic acid;
“?HIB? “?HIB?” means hydrophilic bases.
“?MBR? means membrane bioreactor;”
“?MCL? means maximum contaminant levels;”
“?MD? means molecular dynamics;”
“?MPD? means m-phenylene diamine;”
“?MWCO? “?MWCO?” means molecular weight cutoff;
“?NO? means nano-object;”
“?P(BASS-S-CMS)? means poly (tetrabutyl ammonium styrene sulfonate-co-styrene-co-4-chloromethyl styrene);”
“?PA? means polyamide;”
“?PAC? “?PAC?” means powder activated carbon;
“?PAN? means polyacrylonitrile;”
“?PDA? means phenylene diamine;”
“?PES? “?PES?” means polyethersulfone.
“?PP? means polypropylene;”
“?PPCP? “?PPCP?” means personal care product.
“?PS? means polysulfone;”
“?PSSA? “?PSSA” means polystyrene-sulfonic acid.
“?PTFE? means polytetra-fluoro-ethylene;”
“?PVC? means polyvinyl chloride;”
“?PVDF? means polyvinylidene fluoride;”
“?r-GO? “?r-GO?” means reduced graphene dioxide;
“?RO? means reverse osmosis;”
“?SEM? “?SEM?” means scanning electron microscopy.
“?TEA? “?TEA?” means triethanolamine;
“?TEM? means transmission electron microscopy;”
“?TFC? “?TFC?” means thin-film composite.
“?TMC? means trimesoylchloride;”
“?TOC? “?TOC?” means total organic carbon.
“?UF? “?UF?” means ultrafiltration.
“?ZNC? means nanocrystals.”
“Refer to FIG. “With reference to FIG. 1, a schematic illustration is provided of a water permeable water membrane for water purification system. Water permeable membrane 10 comprises porous support 12, and a composite layer 14, which is disposed on top of the porous support. Composite layer 14 contains graphene oxide, which is dispersed in a polymer matrix. Composite layer 14 has a thickness of approximately 10 nm. Some variations of composite layer 14’s thickness are greater than others in increasing order, such as 5 nm or 10 nm. 50, nm and 100 nm. 50 nm. Other variations of composite layer 14 have a thickness that is lower than in increasing order. These include 1 mm or 0.1 mm. 1000, 500, nm and 200 nm. Porous support 12 can also include an optional fabric layer 18, which is typically disposed over the polymeric layer 16.
“With reference to FIG. “With reference to FIG. 2, a schematic illustration is provided of a water purification device using the water permeable material set forth above. This water purification system works in reverse osmosis. Water purification system 20 comprises chamber 22. It has a first water storage section 24 that holds impure water, and a second water storage section 26 that holds purified water. The water permeable membrane 10, which is water, is placed between the first and second water holding sections 24 and 26. Water purification system 20 can also include a pressure applicator 28, which is a pump that applies pressure to impurify water in the first section 24. This allows water to permeate through the water permeable membrane 10 and into the second section 26. The pressure regulator 30 maintains the water holding section 24 at a constant level. Through inlet 32, impure water can be introduced to water purifications systems 20 during operation. Under pressure, the water enters first section 24 through pressure applicator 30, One refinement shows that first water holding section 24 can be operated at pressures ranging from 20 to 1500 PSI. Another refinement calls for first water holding section 24 to be operated at a pressure of between 30 and 250 psi. Another refinement is that first water holding section 24 can be operated at 600 to 1200 PSI. Water moves across a water permeable membrane 10 when it is held at a higher pressure. Water section 10 contains water that is purer than the original water. Purified water exits via outlet 34, while water with concentrated impurities exits via outlet 36.”
“The water permeable membrane according to the invention of the present invention, includes graphene dioxide and graphene nanostructures. While the exact structure is not known, it seems to contain sections of graphene that have been?oxidized?. Areas that are water-permeable indicate a chemical modification to graphene. The graphene oxide nanostructures can be varied in size and shape. The thickness of the membrane is not limiting. It can be as thin as a few nanometers to several microns or even several millimeters.
“Graphene oxide” is partially oxidized graphene with carboxyl,hydroxyl and epoxide functional group that makes it water-soluble. The graphene dioxide is a reduced grapheneoxide. GO’s nano-sized structures will typically have a spatial dimension of less than a micron. Other refinements may result in nano-sized structures having a smaller spatial dimension than 500 nm or 100 nm. Or on the order of several nanometers. Other refinements may have a larger spatial dimension than 3 angstroms or more than 5 angstroms. Another refinement shows that graphene oxide can have a spatial dimension of 10 nn to 500 nm. The graphene dioxide is typically present in an amount of between 0.05 and 20 weight percent of total weight of grapheneoxide and polymer matrix. Some refinements may result in graphene dioxide being present in an amount higher than 0.01 weight percent. 0.05 weight percentage, 1.0 weight%, 2.0 weight%, or three weight percent of the total weight of the grapheneoxide and polymer matrix. Some refinements may have the graphene dioxide present in a lower amount than 50, 30, 40, 20, 20 and 10 weight percent respectively.
“The water permeable membrane according to the invention comprises a polymer matrix in which graphene oxide is dispersed. Examples of suitable polymeric matrixes include, but are not limited to, cellulose acetate, nitrocellulose, and cellulose esters (CA, CN, and CE), polytetra-fluoro-ethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyacrylonitrile (PAN), polyamides, polyimides, polyvinyl chloride (PVC), polysulfone (PS), polyether sulfone (PES) polyether sulfone (PES), polyethylene and polypropylene (PE and PP). This is especially true for polyamide and a cross-linked matrix of polyamide. Polyamide can be sulfonated or not. The polyamide can be an aromatic polyamide with C6-12 aromatic groups. Another useful polymer matrix is a sulfonated or non-sulfonated poly (tetrabutyl ammonium styrene sulfonate-co-styrene-co-4-chloromethyl styrene)-polyvinylidene fluoride blend.”
“A. “A.
“Materials that include polymers with different molecular masses and distributions, as well as degree of branching, can be synthesized and characterized using solid and solution state characterization methods. Changes in polymer polarity induced by systematic changes in polymer composition may be carried out by copolymerization and/or chemical-functionalization. Copolymerization has many advantages, including the ability to produce consistent chemical compositions. These examples have been shown above. The most promising for performance are aromatic polyamides. There are several possible routes, including: (a) Chain topology, i.e. Increases in chain branching through the addition of branching unit in the diamine For instance, small variable fractions of 1,3,5-triaminobenzene may be added in order to increase segments densities. (b) A second and promising approach is chemical modification of the polyamide (PA) through chemical modification of the polyamide backbone through changes in the copolymerization of trimesoyl chloride with 2,4-diamino-N,N-dimethylaniline, 1, along with 1,3-phenylenediamine (PDA) (also known as m-phenylenediamine or MPD) as illustrated in FIG. 3. The chemical structure can be further modified by the transformation of 1 into copolymers 3, and 4, where 3 has a anionic character, while 4 is a neutral copolymer with a zwitterionic secondary ammonium sulfurate copolymer (FIG. 3). These structures are those of a copolymer in which the molar ratio [phenylene dimamine]/[1] equals 2. You can easily adjust the ratio to alter the ionic characteristics and degree of functionalization. It should be kept to a minimum as too much ionic functionalization could lead to a decrease in salt rejection, organic rejection, or filtration selectivity.
“B. Polyamide-Nanomaterial Composites.”
“The addition nano-objects into the polymer matrixes will affect the surface and bulk properties. This can be controlled through modular membrane synthesis protocols. The dramatic effects of adding GO to water flow are evident in the following studies. It is possible to synthesize GO from graphene (Suk et. al. ACS Nano, 4(1), 6557-6564 2010, 2010; Zhu et. al. Advanced Materials 22 (35) 3906-3924 2011, 2011). This will allow for greater control over reproducibility and the effects oxidation conditions have on chemical structure. Further chemical functionalization will be possible (see below).
“Various embodiments may include the incorporation of hydrophilicNOs to an aromatic polyamide matrix (PA) (FIG. 4) by interfacial polymerization (MPD, trimesoyl chlorineide (TMC), precursors with MPD containing different amounts of NOs. These nanocomposites can be functionalized with carbon-based nanomaterials like CNTs or GOs. Two-dimensional capillaries made of closely spaced graphene sheets have been suggested to allow water to flow with low friction (Nair and al., 2012). Suk et. al. (2010) also found that GO has strong chemical and mechanical stability. GO has antibacterial properties which would reduce the microbial attack of membranes (Hu et. al., ACS Nano 4(7), 4317-4323 in 2010; Liu et. al., ACS Nano 5(9), 6971?6980 in 2011). The GO particles may be added to various phenylene diamines in variable quantities so that the scalability as reverse osmosis/nanofiltration membrane material and the effects on aqueous flow properties can be evaluated. This allows membrane selectivity to be maintained while optimizing water flux and antifouling properties. This can be done with any of the four main polymer matrix types: (a) neutral PA; (b) PA copolymer modified using varying fractions quaternary ammonium haides; (c) PA functionalized by sulfonated zwitterions and (d) partially-sulfonated anions PA (FIG). 5).”
“This chemical modification of copolymers 3 & 4 can be compared to the sulfonic Acid copolymer product, 5 Both cases show that the hydrophilicities are controlled by the PAs.
“Functionalization Of Graphene Oxide.”
To reduce biological fouling, a surface functionalization using nano-objects (NOs), could be performed. This could include the carbodiimide-mediated functionalization carboxylic groups into anamide that carries at least a tertiary amino (FIG). 6). This will then be alkylated to produce a Tertiary Ammonium Halide (structures unknown) and the introduction a Zwitterionic Ammonium Sulfonate by reaction of an amine with a sulfurone (FIG. 6). The first case introduces a cationic charged, while the second is electrostatically neutral. These changes will allow us to better understand the issue and help to define its scope. These variations can all be tracked and evaluated through intra-campus collaboration between members of both research teams.
“Membrane Characterization.”
“Surface characterization can be done using scanning electron microscopy and transmission electron microscopy. Monitoring changes in the surface energies can help determine the structural and physicochemical impacts on the surface, for example by atomic force microscopy, surface energies and altered morphologies of inner (bulk), membranes. These are then studied using transmission and surface electron microscopes (SEM/TEM respectively). Materials made up of polymers with different molecular masses and distributions, as well as branching degrees, can be synthesized and characterized using both solid-state and solution characterization methods (see below). Changes in membrane hydrophobicity induced by systematical changes in polymer compositions may be carried out by copolymerization or end-functionalization that has potential for considerable structural control. Nano-objects can be added to polymer matrices. This will have an impact on the surface and bulk properties. Modular membrane synthesis will allow for considerable control. This will also affect the pore sizes and shapes.
“Membrane Fouling Control & Cleaning Strategies”
“In the contexts of membrane synthesis, development, and membrane fouling in integrated processes are important. These factors include colloids, extracellular polymers, inorganic precipitates, scalants and biomass. They are affected by process operating conditions. These factors are responsible for membrane fouling in these systems: (i. macromolecular and collloid sorption; (ii. biofilm growth and attachment); and (iii. inorganic precipitation and scaling. (Tsai and Pirbazari in Journal of Environmental Engineering and Science 3(6), 507-521 in 2004; Williams and Pirbazari in Water Research 41 (17), 3880-3893, 2007; Ravindran and colleagues in Journal of Membrane Science. 344(1-2), 39-54, 2009). Fouling can be caused by the absorption of hydrophobic substances onto and within membrane pores and the deposition of a cake or gel layer on membrane surface. Extracellular polymeric substances (EPS), which mainly contain carbohydrates, proteins and nucleic acid, are the main causes of biological fouling (Williams et al. 2007; Ravindran, et al. 2009). Powder activated carbon (PAC), an adsorbent, and fluid management can reduce permeate flux and prevent membrane fouling (Williams, Pirbazari and Ravindran, 2009; Williams and et. al. Chemical Engineering Science, 84,511, 2012). The PAC removes dissolved biological and other matter from the water and re-entrains colloids, suspended solids and liquids from the viscous layer. It absorbs all organic and bio-organic pollutants in wastewaters and reclaimed water, including proteins, carbohydrates, and fats (Kilduff andWeber, Environmental Science and Technology 26 (3), 569-577 1992). PAC reduces the thicknesses of hydrodynamic and mass-transfer boundary layers, lowers concentration polarization and controls gel deposition on membrane surface or pores (Pirbazari et. al. Water Research, 30(11), 2691-2706, 1996; Tsai et. al. Journal of Environmental Engineering and Science 3(6), 507-521 2004, Ravindran et. al. 2009).
Concentration polarization suppression, optimization of chemical and physical cleaning protocols and pre-treatment of feed can all be used to control membrane fouling (Tu et.al., Journal of Membrane Science 265 (1-2), 29-50; Williams and Pirbazari 2007, 2007). For flux recovery and maintenance of rejection, fouling control, flux recovery and rejection maintenance are all important aspects of membrane cleaning strategies. For removing hydrophobic substances and other major contributors to organic, biological, or organic fouling, the efficacy of different cleaning agents, such as acids, surfactants and enzymes, may be evaluated. It may also be possible to determine the chemical tolerance of these cleaning agents.
“The synthesis of new RO membranes can be achieved using the materials described in this document. They have enhanced water flux, improved resistance to organic, biochemical fouling, scaling, and other degradation processes.”
“Graphene oxide, a nano-sized material that is synthesized through controlled oxidation graphite, can be found in a variety of commercially affordable materials. GO, a nano-sized structure, will typically have a size range of less than 0.1 micron. Other refinements may result in nano-sized structures having sizes ranges less than 500 nm or 100 nm. Or on the order of several nanometers. Other refinements may allow for sizes that are greater than 3 angstroms or 5 angstroms. Partially oxidized graphene (GO) contains carboxyl, hydrol, and/or epoxide functional group that make it water-soluble. GO can also be dissolved in organic solvents. It is well-known for its strong chemical and mechanical stability (Suk et.al., ACS Nano 2010, 4(11), 6557-66564; Dmitriy et.al. Nature 2007, 448-457-460). GO also has antibacterial properties (Liu et al., ACS Nano, 2011, 5(9), 6971-6980; Hu et al., ACS Nano, 2010, 4(7), 4317-4323). When GO is used as an active layer, or mixed with a polysulfone membrane (PS), it has been shown that it can only be used as a microfiltration and nanofiltration membrane because there are no blocking monovalent ions. Sci. Sci.
“Embodiments described herein incorporate GO in aromatic PA matrices via interfacial Polymerization of trimesoyl chloride and phenylene diamines (PDA), which both contain varying amounts of Go’s. The high salt rejection of PA membranes means that they can also be used as ultrafiltration membranes (UF). The incorporation of GO to PA could promote UF or desalination processes. This is done by putting GO’s onto the PA surface in the final stages of polymerization, or in the bulk through the dissolution of GO?s into the PDA solution.
“Initial work consisted of the development of polymer-synthesis protocols that included appropriate reaction schemes, free radical processes, syntheses conditions like reaction times, curing methods, and quantitatively controlled infusion of graphene oxide. These conditions were modified to produce superior membranes. These membranes were prepared using interfacial polymerization with sequential addition of MPD, TMC on a commercially available polyether sulfone ultrafiltration membrane base. It has a nominal pore diameter of 0.08 microns and a molecular weight cutoff (MWCO), of 10,000 Daltons. This ultrafiltration membrane is the most effective commercially available for water reclamation and other related applications. Monomers used to prepare polyamide membranes were m-phenylene dimamine (MPD), 1,3,5-benzene trimesoyl chloride (TMC) and 1,3,5 benzene tricarbonyl chloride (TMC). These monomers MPD, TMC were used to create another set of membranes. However, camphor sulfonic (CSA) was added to the mix to increase the solvophilicity of the membranes and observe their rejection, aqueous transport, and hydrophilicity.
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