Abstract:Graphene oxide (GO) nanosheets were attached to the polyamide selective layer of thin film composite (TFC) forward osmosis (FO) membranes through a poly L-Lysine (PLL) intermediary using either layer-by-layer or hybrid (H) grafting strategies. Fourier transform infrared spectroscopy, zeta potential, and thermogravimetric analysis confirmed the successful attachment of GO/PLL, the surface modification enhancing both the hydrophilicity and smoothness of the membrane's surface demonstrated by water contact angle,… Show more
“…GO coatings can also work as a surface modifier to increase water permeability, suppress salt reverse flow, and improve antifouling ability of FO membranes. Ginic‐Markovic et al developed two methods, LbL strategy and hybrid (H)‐grafting strategy, to attach GO on the surface of TFC PA FO membrane via poly L‐lysine (PLL). After GO/PLL surface modification, water permeability maintained almost the same as the neat PA membrane, whereas the reverse flow (2 m NaCl draw solution) of GO/PLL‐H membrane dramatically decreased 63% and that of GO/PLL‐LBL membrane increased 78%.…”
Section: Go Functional Coatings On Membranesmentioning
a significant advantage, greatly facilitates GO deposition from solution using water as a low cost and environment-friendly solvent. [3] Recently, GO has attracted great attention as a novel 2-D membrane material in water purification application because of its excellent mechanical property, atomically thin thickness, excellent dispersion in water, and ease to form compact membrane structure or to be added into polymer matrix. [3,4] Concept demonstration/preliminary studies on using graphene-based membranes for water purification were focused on simulations for single layer graphene/ GO/reduced GO (rGO) with structural defects. Cohen-Tanugi et al., [5] using molecular dynamics (MD) simulation, found that hydrogenated and hydroxylated defects with appropriate sizes on graphene could have 2-3 orders of magnitude higher water permeability than commercial reverse osmosis (RO) membranes but similarly high salt rejection, suggesting great potential of single-layered graphene membranes for desalination. Lin et al. [6] showed by MD simulations that thermally reducing GO with different initial epoxy to hydroxyl ratios and different oxygen concentrations may generate selective defects on rGO for high water permeability and high salt rejection desalination. Figure 2a shows representative structures of rGO after reduction at 2,500 K, when GO flakes with different starting oxygen concentrations and epoxy concentrations or epoxy/hydroxyl ratios are used. With the increase of oxygen concentration and epoxy concentration, rGO becomes more defective and has bigger nanopores because of more carbon removal from the GO matrix. This suggests pores on rGO may be controlled by controlling starting GO composition and reduction conditions. Further, they studied desalination performance of defects on rGO after reduction at different temperatures and using GO with different oxygen concentrations and epoxy concentrations (Figure 2b). Too low oxygen concentration (17%) leads to complete water blocking irrespective of reduction temperature and initial epoxy concentration or epoxy/hydroxyl ratio. At higher initial oxygen concentration (25% and 33%), high water flux and 99% salt rejection can be obtained depending on reduction temperature epoxy/hydroxyl ratio. These promising simulation results, therefore, suggest appropriately reducing GO with desired starting composition As a newly emerging 2-dimensional (2-D) material with sub-nanometer thickness, graphene oxide (GO) has been widely studied either as a pure/skeleton membrane material or as an additive in and a functional coating on matrix membranes for water purification because of its unique physico-chemicomechanical properties. Manipulating or incorporating this novel 2-D material effectively into a membrane structure has been shown to significantly improve membrane performance, including increased water permeability, alleviated fouling, improved antibacterial properties, etc., which will eventually lead to lower energy consumption, longer lifetime, and lower maintenance cost. As the pure/...
“…GO coatings can also work as a surface modifier to increase water permeability, suppress salt reverse flow, and improve antifouling ability of FO membranes. Ginic‐Markovic et al developed two methods, LbL strategy and hybrid (H)‐grafting strategy, to attach GO on the surface of TFC PA FO membrane via poly L‐lysine (PLL). After GO/PLL surface modification, water permeability maintained almost the same as the neat PA membrane, whereas the reverse flow (2 m NaCl draw solution) of GO/PLL‐H membrane dramatically decreased 63% and that of GO/PLL‐LBL membrane increased 78%.…”
Section: Go Functional Coatings On Membranesmentioning
a significant advantage, greatly facilitates GO deposition from solution using water as a low cost and environment-friendly solvent. [3] Recently, GO has attracted great attention as a novel 2-D membrane material in water purification application because of its excellent mechanical property, atomically thin thickness, excellent dispersion in water, and ease to form compact membrane structure or to be added into polymer matrix. [3,4] Concept demonstration/preliminary studies on using graphene-based membranes for water purification were focused on simulations for single layer graphene/ GO/reduced GO (rGO) with structural defects. Cohen-Tanugi et al., [5] using molecular dynamics (MD) simulation, found that hydrogenated and hydroxylated defects with appropriate sizes on graphene could have 2-3 orders of magnitude higher water permeability than commercial reverse osmosis (RO) membranes but similarly high salt rejection, suggesting great potential of single-layered graphene membranes for desalination. Lin et al. [6] showed by MD simulations that thermally reducing GO with different initial epoxy to hydroxyl ratios and different oxygen concentrations may generate selective defects on rGO for high water permeability and high salt rejection desalination. Figure 2a shows representative structures of rGO after reduction at 2,500 K, when GO flakes with different starting oxygen concentrations and epoxy concentrations or epoxy/hydroxyl ratios are used. With the increase of oxygen concentration and epoxy concentration, rGO becomes more defective and has bigger nanopores because of more carbon removal from the GO matrix. This suggests pores on rGO may be controlled by controlling starting GO composition and reduction conditions. Further, they studied desalination performance of defects on rGO after reduction at different temperatures and using GO with different oxygen concentrations and epoxy concentrations (Figure 2b). Too low oxygen concentration (17%) leads to complete water blocking irrespective of reduction temperature and initial epoxy concentration or epoxy/hydroxyl ratio. At higher initial oxygen concentration (25% and 33%), high water flux and 99% salt rejection can be obtained depending on reduction temperature epoxy/hydroxyl ratio. These promising simulation results, therefore, suggest appropriately reducing GO with desired starting composition As a newly emerging 2-dimensional (2-D) material with sub-nanometer thickness, graphene oxide (GO) has been widely studied either as a pure/skeleton membrane material or as an additive in and a functional coating on matrix membranes for water purification because of its unique physico-chemicomechanical properties. Manipulating or incorporating this novel 2-D material effectively into a membrane structure has been shown to significantly improve membrane performance, including increased water permeability, alleviated fouling, improved antibacterial properties, etc., which will eventually lead to lower energy consumption, longer lifetime, and lower maintenance cost. As the pure/...
“…The bacterial strain grew well on the pristine membrane at zero time and its growth was further enhanced after 24 h. Generally, all the pTA-f-GO membrane samples displayed a high bactericidal activity of at least 82% reduction in the bacterial colonies of E. coli compared to the pristine membrane, with the pTA-f-GOH membrane showing the highest antibacterial ability (83.8%). This can be attributed to the presence of f-GO that inhibits bacterial growth due to the presence of reactive oxygen species (ROS) along with its sharp edges 24, 39 . In addition, previously there has been shown to be a synergetic effect when combining pTA-pEI and GO, providing the fabricated pTA-f-GO membranes with their high biocidal effect following the capturing and killing mechanism 18 .Figure 6The biocidal activity of the pristine and pTA-f-GO TFNC fabricated membranes as a function of GO concentration.
…”
A practical fabrication technique is presented to tackle the trade-off between the water flux and salt rejection of thin film composite (TFC) reverse osmosis (RO) membranes through controlled creation of a thinner active selective polyamide (PA) layer. The new thin film nano-composite (TFNC) RO membranes were synthesized with multifunctional poly tannic acid-functionalized graphene oxide nanosheets (pTA-f-GO) embedded in its PA thin active layer, which is produced through interfacial polymerization. The incorporation of pTA-f-GOL into the fabricated TFNC membranes resulted in a thinner PA layer with lower roughness and higher hydrophilicity compared to pristine membrane. These properties enhanced both the membrane water flux (improved by 40%) and salt rejection (increased by 8%) of the TFNC membrane. Furthermore, the incorporation of biocidal pTA-f-GO nanosheets into the PA active layer contributed to improving the antibacterial properties by 80%, compared to pristine membrane. The fabrication of the pTA-f-GO nanosheets embedded in the PA layer presented in this study is a very practical, scalable and generic process that can potentially be applied in different types of separation membranes resulting in less energy consumption, increased cost-efficiency and improved performance.
“…The first approach enables the good dispersion and strong attachment of the nanomaterial on the membrane surface and enhances the long‐term stability of the nanomaterial. Functionalized graphene has been reported to modify a wide range of membrane types, including MF, UF, NF, RO, and FO membranes, via this approach. For instance, Wang et al modified a PSf membrane surface by cross‐linking GO/epichlorohydrin (ECH) with O‐(carboxymethyl)‐chitosan (OCMC), where GO bound covalently to the amino groups of OCMC.…”
Section: Preparation Of Functionalized Graphene–polymer Membranesmentioning
their energy consumption is much lower than that of thermal approaches. [3] Therefore, membrane technologies are regarded as cost-effective candidates and play an increasingly important role in the treatment of natural waters and wastewaters. [4] Membrane processes for water purification and desalination can be generally classified into microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), and emerging forward osmosis (FO) according to the pore size of the membrane and the respective rejection mechanism. The materials used to fabricate the membranes cover a wide range of polymers and inorganic materials. By far, polymeric membranes are the most widespread type due to their high processability, high flexibility, and low cost. [5][6][7] Traditional asymmetric membranes that contain only one type of polymer are mainly used for UF and a few NF applications. These membranes exhibit an asymmetric porous structure that consists of a thin nano porous active layer and a microporous underlying layer. MF membranes, however, possess a relatively symmetric micro porous structure. These porous membranes are mainly fabricated by phase inversion. For RO, FO, and most NF membranes that reject nanoscale solutes, an individual nonporous, dense, and thin polyamide (PA) active layer is normally required and is deposited onto a porous support layer to ensure a high selectivity. The active layer is prepared via interfacial polymerization (IP), while the support layer can be fabricated by phase inversion. These membranes are known as thin film composite (TFC) membranes, and the layers are comprised of different polymers. TFC membranes possess superior permeability over that of first-generation cellulose acetate membranes. [8,9] Although polymeric membranes have been widely reported in scientific studies and utilized for industrial applications, they are restricted by the inherent limitations of the material, such as a permeability/selectivity trade-off and a low fouling resistance. The current ability to control the membrane structure in both molecular-level design and fabrication process is not satisfactory. [10] In the last decade, the incorporation of nanomaterials into polymeric membranes has gained considerable attention owing to the potential of the resulting materials for overcoming the above limitations. [11,12] These advanced composite membranes have shown enhanced performance with a low loading of nanoparticles (NPs), including zeolites, [13][14][15] silica, [16][17][18][19][20][21][22] Membrane technologies for water treatment and desalination are increasingly developed and utilized to address the global challenges of water security and supply. Membrane-based separations can produce water with desirable qualities from a wide range of water sources, such as groundwater, seawater, brackish water, and wastewater. However, the membranes, which are typically made from polymers, are still restricted by their inherent limitations, including a permeability/selectivity trade-off and a high fouling prop...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
