Impact of dithiocarbamate-based polymeric additives on the performance of polyethersulfone membrane for the treatment of arsenic contaminated waters

Two types of aliphatic and aromatic dithiocarbamate (DTC) polymers, having the thioamide groups were synthesized and used as hydrophilic agents as well as arsenic adsorbents in fabrication and modification of polyethersulfone (PES) membranes for the separation of arsenic from the contaminated water. The synthesized DTCs were characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR), and their arsenic adsorption test demonstrated arsenic removal of 85.5% and 91.4% for the aromatic and aliphatic DTC polymers respectively. The results indicated that by increasing the concentration of DTCs, both membrane flux and rate of arsenic removal increased compared to the bare one. The water flux reached a maximum value at 0.5 wt% DTCs and further increase lead to decreased flux. The aliphatic DTC behaved better than the aromatic one: the membrane with aromatic DTC showed better arsenic rejection than the aliphatic one, corresponding well to the adsorption results. The water contact angle was reduced by the addition of DTCs, indicating increased hydrophilicity. The fouling resistance increased by the addition of DTCs which was demonstrated by increased flux recovery ratio (FRR) after BSA fouling. The real arsenic polluted groundwater treatment for a long-time showed that tailored-made DTC polymers are excellent candidates for arsenic removal and improvement for the fouling resistance of PES membranes.