SURFACTANT-MEDIATED SEPARATION PROCESSES - SURFACTANT-ENHANCED CROSS-FLOW FILTRATION IN NITRATE REMOVAL FROM WATER

Removal of nitrate from water was studied using the surfactant-enhance d crossflow filtration (SECF) technique with the cationic surfactant, hexadeclytrimethylammoniumbromide (CTAB). The variation of nitrate and surfactant rejections and permeate flux with time were measured as a function of CTAB/nitrate ratio, transmembrane pressure drop (Delta P), membrane pore size, pH of the feed solution, and electrolyte (NaCl) c oncentration. The method was found to be effective in removing nitrate from water. It was observed that the efficiency of nitrate removal in creased with increasing CTAB/nitrate ratio. Nitrate and CTAB rejection s decreased with increasing electrolyte concentration, while pH did no t have any significant direct effect on rejection. The pseudo-gel conc entration (C-g()) determined from the linear portion of steady-state permeate flux versus log (C-SF) was 18 gl(-1), where C-SF is the surfa ctant feed concentration. It was observed that even when C-SF was grea ter then C-g() there was a certain amount of permeate flux. The effic iency of the process was shown to be higher for larger membrane pore s ize.