Table 2 Surface coating or grafting of polyamide membranes
Materials | Treatment | Fabrication method | Salt rejection | Water permeability | Tolerance Test (Chlorine and antifouling) | Modification properties affecting the tolerance | References |
|---|---|---|---|---|---|---|---|
Base structure of X3SiRY, where X is a –OC2H5 alkoxy group and Y is an alkyl (CH3, C8H17, or C18H37), vinyl. | Heat treatment | Coating | [NaCl]: 3500 ppm, R: 96.00–99.52 | 0.255–1.114 L/m2 h 55 kgf/cm2 | [NaClO]: 2000 ppm 12 h | Alkyl and aryl groups | |
poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-co-Am)) | __ | Interfacial polymerization, Coating | [NaCl]: 2000 ppm, R: 95.2% | 45 L/m2 h, 1.5 MPa | [NaClO]: 3000 ppm, 1 h acid stability, chlorine resistance | Replace hydrogen with chlorine which enhanced intermolecular hydrogen bonding | |
Hydantoin derivative, 3-monomethylol-5,5-dimethylhydantoin (MDMH) | Heat curing at 80 °C | Free radical graft polymerization | [NaCl]: 200 ppm, R: 89%–90.5% | 94.8–117.4 L/m2 h | [NaOCl]: 100–2000 ppm, chlorine resistances, anti-biofouling | Sterilize microorganisms on membrane surfaces, regenerate to MDMH | |
3-allyl-5,5-dimethylhydantoin (ADMH) using 2,2 - azobis(isobutyramidine) dihydrochloride as an initiator | __ | Grafting polymerizations | [NaCl]: 2000 ppm, R: 85% | 205 L/m2 h 1.5 MPa | (100–2500) ppm 1 h chlorine resistance, anti-biofouling property | Sacrificial pendant groups | |
3-allyl-5,5-dimethylhydantoin (ADMH) and then crosslinked by N,N′-Methylenebis(acrylamide) (MBA) | Heat treatment | Free-radical graft polymerization | [NaCl]: 2000 ppm, R: 96.9% | 86.3 L/m2 h 1.5 MPa | [Free chlorine]: 1000 ppm, 1 h Enhance chlorine resistances and anti-biofouling properties | Presence of high amount of N atom, increased in hydrophilicity of membrane. MBA with amide II groups in aliphatic and MBA cross-linked aromatic PA | |
Imidazolidinyl urea | __ | Carbodiimide-induced graft copolymerization | [NaCl]: 2000 ppm, R: 93.6% | 150 L/m2 h 1.55 MPa | [NaClO]: 1000 ppm, 100 days | IU grafted as sacrificial pendant groups | |
Carbodiimide-induced graft copolymerization with Poly (ethylene glycol) derivatives |  | Interfacial polymerization Jeffamine ED600 modified membrane Jeffamine ED2001 modified | [NaCl]: 1500 ppm R: 96.4% R: 96.5% | 1.05 MPa 32 L/m2 h 36 L/m2 h | [Mlk]: 100 ppm, (DTAB, a cationic surfactant): 100 ppm, 5 h No adsorption of protein | Good steric repulsion | |
Glycylglycine Gly-grafted PA membrane | __ | Interfacial polymerization Grafting | [NaCl]: 2000 ppm R: 90% | 3.7 L/m2 h 1.6 MPa | [NaClO]: 1000 ppm, 1 h | Sacrificial pendants: N–H moiety of glycylglycine | |
Poly(ethylene glycol) (PEG) diglycidyl ether (PEGDE) | Heat treatment | Grafting | [NaCl]: 2000 ppm, R: 99% | 40–60 L/m2 h 5.5 bar | [Surfactant] or [oil-in-water emulsion]: 150 ppm, 30 h preventing foulants from closely approaching the membrane surface | Steric hindrance by PEG | |
Graphene oxides coated by tannic acid (GOT) | __ | -Interfacial polymerization -Coating | [NaCl]: 2000 ppm, R: 90% | 44 L/m2 h 15.5 bar | [NaClO]: 500 ppm, 1 h -antimicrobial and anti- oxidant properties - tissue engineering, battery membranes, sensing, and gas se- paration processes | GOT enhanced oxidative stress capability, barrier property and hydrophilicity | |
Azide-functionalized graphene oxide (AGO) | UV exposure | Coating | [NaCl]: 2000 ppm [BSA]: 200 ppm R: 95.3% | 36.3 L/m2 h | 17-fold reduction in biofouling | Grafting of GO reduced the tendency to form gel layer so less accumulation of foulant. foulant deposition. | |
Sulfonated polyvinyl alcohol (SPVA) | Cross-linking treatment | Coating | [NaCl]: 2000 ppm, R: 99.18% | 38.3 L/m2 h 1.55 MPa | 2000 ppm of BSA, 12 h improved fouling resistance to BSA and CTAB | Electronegativity and hydrophilicity of PA-SPVA and strong ionization of sulfonic acid group. | |
Glutaraldehyde aqueous solution followed by polyvinyl alcohol (PVA) aqueous solution | Sequential surface treatment with glutaraldehyde (GA) | Coating | [NaCl]: 500 ppm, R: 98.48 −97.29% | 28.6–40.9 L/m2 h, 5 bars | [NaOCl]: 5000 ppm -6 h Chlorine stability -Anti-fouling property | Enhanced surface hydrophilicity, reduced surface negative charge and increased surface roughness. Covalent attachment of PVA | |
Terpolymer of 2-acrylamido-2-methyl propane sulfonic acid, acrylamide and 1-vinylimidazole (P(AMPS-co-Am-co-VI)) | __ | - Conventional free radical. - dip-coating process | [NaCl]: 80,000 ppm R: 85% | 45 L/m2 h 0.4 MPa | [NaClO]: 2000 ppm, 40 h improve the chlorine tolerance | Terpolymer as a barrier layer |
