Novel reverse osmosis membranes incorporated with a hydrophilic additive for seawater desalination

Novel thin-film-composite reverse osmosis membranes were synthesized successfully for seawater desalination by incorporating the hydrophilic additive, o-aminobenzoic acid–triethylamine (o-ABA–TEA) salt, into the aqueous m-phenylenediamine (MPD) solution to react with trimesoyl chloride (TMC) in the organic solution during the interfacial polymerization on a nanoporous polysulfone support. The membrane synthesis conditions, including o-ABA–TEA salt concentration, isopropanol (IPA) concentration, additional amine drying time, and hydrocarbon removal time, were optimized by characterizing membrane performances using synthetic 3.28 wt% NaCl solution under seawater desalination conditions at 800 psi (5.52 MPa) and 25 °C. The synthesized membranes showed a very high flux of 1.81 m3/m2/day (44.4 gallons/ft2/day (gfd)) and a salt rejection of 99.41%. The improvement of membrane hydrophilicity was confirmed by comparing the contact angles of the membranes synthesized with and without the hydrophilic additive. The high-flux membrane was further tested using seawater from Port Hueneme, CA and exhibited a very good and stable desalination performance for 30 days. The fouling-resistant properties of the membranes synthesized with and without the hydrophilic additive were evaluated by using sodium alginate, a common contaminant derived from seaweed, as the model foulant. The membrane synthesized with hydrophilic additive showed significantly smaller water flux decline. The surface morphologies of the membranes were analyzed using atomic force microscopy (AFM). The results showed a smoother membrane surface for the membrane incorporated with the hydrophilic additive.