Year Coating agent Purpose Performance Ref 1998 PEO with octylphenol or polypropylene oxide head group cost savings by surface modification Decline in flux relative to untreated membrane, only T-X 100 improved rejection significantly, P-F87 was the only treatment that resulted decline in rejection after fouling, surfactant cause decrease in roughness without a large change in zeta potential after fouling. 29 2006 Polyether-polyamide block copolymer (PEBAX) To see effect on membrane fouling and performance Coating reduced surface roughness without significant change in CA, enhanced fouling resistance against a model oil/surfactant/water emulsion feed, the coating reduced water flux whithout change salt rejection, coating remained on the surface of the membranes after 106 days of filtration. 30 2009 Polyethyleneimine (PEI) To improve antifouling properties Coating reduced pure water permeability by 37%, by increase in the PEI concentration, flux decreased (from 23.

5 L/m2 h to 15 L/m2 h), salt rejection improved from 77.9% to 82.2% for NaCl and from 72.2% to 91.2% for MgCl2, improved fouling resistance and the increased surface hydrophilicity. 31 2009 PEG based coating (poly ethylene glycol diacrylate + poly ethylene glycol acrylate, 2-hydroxyethyl acrylate, or acrylic acid) To increase fouling resistance. Coating reduced the water flux of membrane, salt rejection of both coated and uncoated membranes is 99.0% or higher, coating caused small reduction in the negative charge of membranes, negatively charged membranes fouled extensively in the presence of positively foulant and minimal fouling in the presence of negatively foulant, more resistant of coated membranes to fouling in surfactant feed solutions and in an oil/ water emulsion made with DTAB 32 2010 Polyethylene glycol acrylate (PEGA) followed by Glutaraldehyde (GA) crosslinking To increase fouling resistance.

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Reduction in Contact Angle (from 49.2 for bare membrane to 45.6) and surface roughness by coating, The pure water flux decreased with increasing the PEGA concentration and increasing GA concentration, exhibited better antifouling properties, recovered 100% of their initial water flux after physical cleaning. 33 2010 poly(N-isopropylacrylamide- co-acrylamide) P(NIPAM-co-Am) To check performance of modified membrane roughness by coating (from 87 nm to 106), decrease in CA from about> 55 for the unmodified membrane, increase in CA by increasing environmental temperature, little influence of coating on salt rejection (between 97% and 98% as that of the original membranes), decreases of water flux by increasing coating concentration, good durability and high performance stability of coating layer. 34 2010 Polydopamine (PDA) deposition followed by PEG-NH2 grafting Effect on flux and foulant adhesion resistance. coating exhibited a small decrease in flux with increasing PDA deposition, PEG grafting reduced RO flux, PDA deposition reduced BSA adhesion and more BSA adhesion reduction was observed when PEG grafting. 35 2010 Polyamidoamine (PAMAM) and PAMAM– polyethylene glycol (PAMAM–PEG) Reduce contact angle and increase biofoulants and organic pollutants resistance. Coated membranes had reduced flux (from 0.

11 mL/cm2 min for uncoated membranes to 0.08 mL/cm2 min for coated membranes) without salt rejection (about 99%), reduction in CA (from 60° to 15°). 36 2011 polyether-polyamide block copolymer (PEBAX): 1 wt% in n-butanol or 1:1 ethanol: water (mass ratio) To enhance water flux Ethanol re-soaking of PEBAX-coated membranes increased the water flux of membranes by almost 70%, from 2.6 L/(m2 h) to 4.5 L/(m2 h) and decrease salt rejection from 96.8% to 95.

4%. 37 2011 Triethylene glycol dimethyl ether (Triglyme) To improve anti-fouling performance. By increasing the time of plasma polymerization, CA reduced and surface roughness increased, lower organic fouling, a little reduction of salt rejection (97.9–98.1%), more reversibility of the fouling 38           2011 P(NIPAM-co-Am) – N-isopropylacrylamide -co-acrylamide To improve acid stability and chlorine resistance By increasing copolymer from 0 to 200 ppm, the CA decreased from 62.5° to 36.6°, and then leveled off, both the water flux and salt rejection of membrane slightly increased at lower coating concentration and then gradually decreased, both of the acid stability and chlorine resistance of the modified membrane increased with increasing the coating concentration. 40 2011 P(NIPAm-co-AAc) – N-isopropylacrylamide-co-acrylic acid To increase NaCl and Na2SO4 rejection and fouling resistance.

Coating increased membrane surface hydrophilicity and surface charge at neutral pH, decreased the salt permeability of NaCl and Na2SO4, improved the fouling resistance to BSA, enhanced cleaning efficiency. 41 2011 P(NIPAM-co-Am) – poly(N-isopropylacrylamide-co-acrylamide) To improve fouling resistance and cleaning efficiency Reduction of CA from about 58.6° to 40.5°with increasing the coating concentration, the pure water permeability slightly increased and then gradually decreased by increasing deposition time, increase in water permeability by 12% and the salt rejection slightly (from 98.5% to 98.9%), improved fouling resistance of membrane to BSA, enhanced cleaning efficiency.

42 2011 HEMA-co-PFDA For antifouling coating. Slight increase in the surface roughness and increase in CA with increasing PFDA content, flux decline (13%) for 20 nm coatings with 40% PFA content for short term permeation tests with DI water. 43 2012 Methyl methacrylate- hydroxyl poly (oxyethylene) methacrylate (MMA-HPOEM) To introduce hydrophilicity and fouling resistance. Slower flux decline of modified membrane than the virgin membrane for BSA (37% and 44%) and seawater, antifouling property against reversible and irreversible fouling of E. coli, durability of coating layer to chemical cleaning. 44 2012 Ring-opening by DMAP followed by SPGE and glycerol coating To improve chlorine resistance.

SPGE membranes were more hydrophilic and smoother, improved chlorine stability, with increasing DMAP concentration, water flux increased and salt rejection decreased, by increasing SPGE concentration water flux decreased and salt rejection increased. 45 2012 PDA deposition followed by PEG-NH2 grafting To improve bioinspired fouling resistance. PDA increased 30–50% water flux and improve the oil/water fouling resistance, the PD-g-PEG coating exhibited no flux decline and no fouling, modified membranes exhibited an increase in irreversible fouling resistance. 46 2012 3-(3,4-dihydroxyphenyl)- L alanine (L-DOPA) To increase flux and fouling resistance. No change in zeta potential after modification, reduction of CA from 55 to 15, intact salt rejection intact (about 97%), increased water flux with increasing the coating duration (1.

27 times of original membrane), improved the BSA adhesion resistance, enhanced the organic and surfactant fouling resistance, high water flux recovery ratio (98%). 47 2012 PEG acrylate multilayers (containing PAA-Alk, PEG-Az or PEG-Alk) To make high flux and fouling resistant membrane. fouling resistance and CA reduction for coated membranes, for seawater membranes, the flux decline 9–17% and salt rejection increase small and for brackish water, no reduction in the flux and slight increase in salt rejection relative of the uncoated value 48 2013 Coating with sericin followed by GA crosslinking To improve fouling resistance. Sericin coating improved surface hydrophilicity, smoothed surface morphology, enhanced negative charge, lower pure water permeability, enhanced salt rejection, improved fouling resistance 49 2013 Polyvinylalcohol (PVA) polyhexamethylene guanidine hydrochloride (PHMG) To enhance anti-biofouling performance Smoothening the membrane surface with all coatings (67.

8 nm for uncoated and lowest RMS for PVA by the value42.5 nm), reduction in CA (from 53.2 for uncoated to15.

9 for PHMG), Lower number of adhered bacteria on all coated membranes, membranes with higher PHMG percentage had higher antimicrobial performance, reduced water permeability and salt rejection after modification. 50 2013 Polydopamine (PDA) To increase flux and fouling resistance. No change in CA with modification of membranes (about 19), decreasing pure water flux and salt rejection with increasing dopamine concentration and deposition time, more resistant of modified membranes to in oil/water emulsion fouling (as judged by higher permeate flux), little effect of variations in dopamine concentration, deposition times, and alkaline pH on the fouling resistance of coated membranes. 51 2013 Polydopamine (PDA) and polydopamine-g-PEG To increase fouling resistance. The PDA-coated RO membranes did not enhance water flux or depress transmembrane pressure difference relative to the unmodified module due to the cleanliness of the RO feed after UF pretreatment, salt rejection was higher and more stable in the modified membrane. 52 2013 Hydroxyethyl methacrylate and perfluoro decylacrylate (PFA) To reduce attachment of bacterial cells. Increasing the PFDA content in the films leaded to increase the CA (from 38 for bare membrane to 64) and surface roughness, increasing the thickness of the coatings increased the surface roughness and decreased the permeation rates (from 170 L/m2 h for bare membrane to 80 L/m2 h for 100 nm coating thickness), by increase the PDFA content the permeation rates of the coated membranes decrease, reduction in cell attachment on the coated surface. 53 2014 P(MDBAC-r-Am-r-HEMA) coating followed by GA crosslinking To improve chlorine resistance and antifouling performance.

Coating decreased flux, increased salt rejection, more tolerance chlorine exposure (7–10 times the pristine membrane), better wettability, fouling resistance, antimicrobial properties. 54 2014 poly2-methacryloyloxyethyl phosphorylcholine (MPC)-co-2-amino ethylmethacrylate (AEMA) (p(MPC-co-AEMA)). For high resistance to bacterial adhesion The coating reduced CA (from 36 of bare membrane to 18.6) and change the surface charge from a negative to a neutral value, decline in water permeability about 20% an increase in salt rejection (from 94.

7 to 96.9), high resistance to bacterial adhesion 55 2014 polydopamine (PDA) To improve antibiofouling potential PDA did not affect the hydrophilicity, surface charge and salt rejection, PDA enhanced the biofouling resistance of membranes, improvement in the bacterial adhesion resistance 56 2014 PDA coating followed by covalently immobilization (MPC-co- AEMA) as the PZ To improve antibiofouling potential No change of hydrophilicity with PDA and/or PZ modification, changing surface charge from negative to neutral by PZ immobilization, permeability and rejection were not affected by modification, enhanced biofouling resistance and lower bacterial attachment of with PZ modification. 57 2014 P(4-VP-co-DVB) deposition followed by reaction with PS to obtain pyridine-based sulfobetaine For prevention of biofouling. Coating decreased surface roughness (from 1.3 nm to 0.8 nm), with the 30-nm coating thickness, the water flux is reduced only by ~14% compared to untreated membranes whiteout changing the salt rejection, the addition of 4% DVB produces a major increase in the resistance to chlorine, whereas additions beyond 4% result in minor additional resistance, good fouling resistance against BSA and bacterial attachment.

58 2014 Hydroxyethyl methacrylate (HEMA) and the hydrophobic perfluoro decylacrylate (PFDA) To reduce attachment of bacteria. By increasing PFDA content, the roughness of surface (< 5 nm) and static contact angle increased, coatings was very smooth and conformal, the intermediate chemistry (40% PFDA) showed less alginate adsorption and highest resistance to bacterial adhesion (2 orders of magnitude). 59 2014 Hydroxyethyl methacrylate (HEMA) and the hydrophobic perfluoro decylacrylate (PFDA) To enhance the biofouling resistance without much affecting permeate flux and salt rejection Deposited film were smooth and conformal, modified surface were initially very hydrophobic but quickly assumed a hydrophilic character within few minutes, modification caused flux decline about 10% of the original value and negligible change in rejection. 60 2014 Atomic layer deposition trimethylaluminium (AlMe3) – (ALD-Al2O3) To reduce Pseudomonas aeruginosa bacterial cells and to optimize process parameter of coating. Coating caused membranes surface tightening, decreasing the roughness, the most hydrophilic surface was obtained with 10 and 50 ALD cycles at temperature 70 °C (16 and 27) and 10 ALD cycles at 100 °C (27), improved antifouling performance of the membrane, the lowest number of bacteria cells was adhered to surface.

61 2014 BaSO4-deposition To increase membrane performance and antifouling property. Mineralized membranes became smoother, more hydrophilic (from 65 of raw membrane to 38.5), more negatively charged, enhanced water flux and salt rejection (from 24.

7 L/m2 h and 96.8% for raw membranes to 29.5 L/m2 h and 98.2% of mineralized membranes), improved antifouling property. 62 2015 P(4-VP-co-EGDA) deposition followed by reaction with 3-BPA to obtain zwitterionic pCBAA To increase fouling resistance. 85% 4-VP is the optimal chemistry for copolymer, zwitterionic coatings reduce CA (from 60.4° for bare membrane to 29°), enhanced resistance against bacterial adhesion, decline in permeate flux (about 17%) and increase in salt rejection (about 2%), stability of copolymer in DI water 63 2015 HPOEM or PEI coating followed by GA crosslinking, then dipping GA-treated PEI membranes in aqueous bromoacetic acid to obtain carboxylated PEI coating To introduce fouling resistance in SWRO membrane.

By surface coating, roughness decreased slightly, HPOEM coating made the membrane less negative and PEI coating made it more neutral, for HPOEM coating, the CA increase from 30.6 to 40.2 and for PEI coating the CA decrease from 57.8 to 43, PEI coating improved fouling resistance in SW feed and HPOEM coating have better fouling resistance under BW feed. 64 2015 p(4-VP-co-EGDA) deposition followed by reaction with 3-BPA to obtain zwitterionic pCBAA To control biofouling. Significant enhancement in resisting biopolymers (BSA and HA) adsorption, reduced attachment of seawater bacterial species. 65 2016 2- acrylamido-2-methyl propanesulfonic acid, acrylamide and 1-vinylimidazole (P(AMPS-co-Am-co-VI)) To improve chlorine resistance. Coated membrane became more hydrophilic (decreased CA to 15), neutral, and smoother, with increasing the coating concentration, the water flux increased and then decreased, the salt rejection increased monotonically, strong chlorine tolerance.

66 2016 2-hydroxyethyl methacrylate-co-perfluorodecyl acrylate (HEMA-co-PFDA) To reduce sodium alginate fouling with low flux decline and unaltered salt rejction. Continuous and dense foulant layer on uncoated membrane while porous and discontinuous one on coated membrane, lower flux decline for coated membrane (10.51% vs. 19.82% for uncoated membrane) without change the salt rejection, better resistance to foulant adsorption, reduction in CA of coated membrane after the deposition of SA (~20) significant decrease (~20°) in the CA of the coated membrane. 67

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