267000 Reverse Osmosis Membranes for Brackish Water Desalination with High Water Flux and Fouling Resistance
Reverse Osmosis Membranes for Brackish Water Desalination with High Water Flux and Fouling Resistance
Lin Zhao, C.-Y. Chang, and W.S. Winston Ho, The Ohio State University
A novel high-flux and fouling-resistant reverse osmosis membrane was synthesized and characterized under brackish water desalination conditions. The o-aminobenzoic acid-triethylamine salt was added into m-phenylenediamine (MPD) solution to react with trimesoyl chloride (TMC) during the interfacial polymerization. The membrane preparation conditions including MPD concentration, TMC concentration, and interfacial polymerization time were optimized using brackish water desalination tests with 2000 ppm NaCl solution at 225 psi and 25oC. The membrane synthesized under the optimal conditions was post-treated with aqueous solutions containing glycerol, sodium lauryl sulfate, and camphorsulfonic acid-triethylamine salt to further increase the water flux. The resulting membrane showed a flux of 54.4 gallons/ft2/day and a salt rejection of 98.6%. This membrane outperformed the other membranes including BW30, LE, XLE, and ESPA3, evaluated at their favorable desalination conditions, respectively. The fouling-resistant property of the synthesized membrane was obtained by physically coating a cross-linked polyethylene glycol (PEG-200) layer on top of the thin film. The effects of cross-linked PEG-200 solution concentration were investigated under brackish water desalination conditions. Dodecyltrimethylammonium bromide, a cationic foulant, caused a 52.9% flux reduction of the uncoated membrane and a 30.8% flux reduction of the coated membrane. Tannic acid, an organic foulant, caused a 15.6% flux reduction of the uncoated membrane and a 4.0% flux reduction of the coated membrane. The modified membrane surface morphology was analyzed using atomic force microscopy and scanning electron microscopy. The results showed a smoother membrane surface which confirmed the successful modification.