Process for improved water flux through a TFC membrane
Provided is a process for preparation of a highly permeable thin film composite membranes for nanofiltration, reverse osmosis, and forward osmosis, particularly for reverse osmosis of brackish water. The process includes treating a prepared TFC membrane containing a discrimination layer on a frontside, a support layer, and a felt layer on the backside by contacting the backside of TFC membrane with a solution containing a pore protection agent that includes a tertiary amine salt of camphorsulfonic acid prior to or at the same time as contacting the frontside of the membrane with a solution containing a coating agent and drying the membrane. Also provided are reverse osmosis membranes prepared in accord with the method, and modules containing the highly permeable thin film composite membranes.
1. A process for improving water flux of a thin film composite (TFC) membrane, comprising:
(a) providing at least one TFC membrane having at least a felt layer on a backside, a support layer, and a discrimination layer on a front side;
(b) applying a backside treatment solution containing from about 0.1 wt % to about 33 wt % of a tertiary amine salt of camphorsulfonic acid as a pore structure protection agent to the backside of the TFC membrane to form a backside-treated TFC membrane; and
(c) drying the backside-treated TFC membrane to yield a treated TFC membrane, the treated TFC membrane having a water flux that is greater than the water flux of a TFC membrane prepared without treating the backside with the backside treatment solution.
2. The process of claim 1 , wherein the tertiary amine of the tertiary amine salt of camphorsulfonic acid is selected from among a trialkylamine having 1 to 6 carbon atoms in the alkyl moiety, a pyridine having 0 to 3 alkyl groups of 1 to 6 carbon atoms, an alkyl-alcohol-amine, an N-alkyl-pyrrolidine having 1 to 6 carbon atoms in the alkyl moiety, an alkylbenzylamine, and a heteroaromatic tertiary amines or a combination thereof.
3. The process of claim 1 , wherein the tertiary amine of the tertiary amine salt of camphorsulfonic acid is selected from among pyridine, 4-dimethylaminopyridine, quinoline, isoquinoline, phenanthridine, triethylamine (TEA), ethyldiisopropylamine, N,N-dimethyl-cyclohexylamine, N-methylpyrrolidine triethanolamine, methyldiethanolamine, ethyl-diethanolamine, dimethylethanolamine, butyldiethanolamine, octadecyl-diethanolamine, cyclohexyldiethanolamine, benzyldiethanolamine. benzylmethyl-ethanolamine, diethyl-ethanolamine, diethyl cyclohexynolamine. methyloctadecyl-ethanolamine, methyl-octadecenylethanolamine, dimethylbenzylamine, and a picoline.
4. The process of claim 1 , wherein the backside treatment solution further comprises a solvent selected from among water, a C 1 -C 4 alcohol, a C 1 -C 4 ketone, a glycol, a polyalkylene glycol, a mono-alkyl ether of ethylene glycol and a di-alkyl ether of ethylene glycol, and a combination thereof.
5. The process of claim 1 , wherein the discrimination layer comprises a polyamide.
6. The process of claim 1 , further comprising applying a coating to the frontside of the TFC membrane.
7. The process of claim 6 , the coating comprising from about 0.1 wt % to about 10 wt % of a polymer selected from among polyvinyl alcohol, polyvinylpyrrolidone, polyethylene, polypropylene, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polystyrene, polyacrylonitrile, polymethyl methacrylate, a polyvinyl acetate polyalcohol, a polyalkylene oxide, a polyimine, a polyacrylic acid, a polyacrylonitrile, a polyamine, a polyurethane, and a polyurea, and derivatives thereof and copolymers thereof.
8. The process of claim 7 , the coating further comprising from about 0.1 wt % to about 40 wt % of a humectant selected from among glycerol, polyglycerol, polyethylene glycol, an alkylene glycol, and a sugar alcohol, and any combination thereof.
9. The process of claim 1 , the drying step comprising heating the treated TFC membrane until a surface of the treated TFC membrane reaches a temperature of at least 75° C.
10. The process of claim 1 , wherein the TFC membrane is a reverse osmosis membrane.