High-flux reverse osmosis membranes incorporated with hydrophilic additives for brackish water desalination

Novel high-flux reverse osmosis membranes with hydrophilic additives were synthesized and characterized under brackish water desalination conditions. Four selected hydrophilic additives, o-aminobenzoic acid-triethylamine salt, m-aminobenzoic acid-triethylamine salt, 2-(2-hydroxyethyl) pyridine, and 4-(2-hydroxyethyl) morpholine, were added into m-phenylenediamine (MPD) solution to react with trimesoyl chloride (TMC) during the interfacial polymerization between MPD and TMC. The effects of different concentrations for each hydrophilic additive were evaluated using brackish water desalination tests with 2000 ppm NaCl solution at 225 psi and 25 °C. After the additive concentration was optimized, the synthesized membranes were post-treated to further improve the water flux using aqueous solutions containing glycerol, sodium lauryl sulfate, and camphorsulfonic acid-triethylamine salt. The resulting membrane showed a flux of 52.6 gal/ft2/day and a salt rejection of about 98.8% or greater. This membrane outperformed the other membranes evaluated, and it also exhibited a good stability in terms of water flux and salt rejection during the entire period of a 30-day test.