Desalination of salt-rich stream from manmade cellulosic fibre industry using commercial nanofiltration membrane: A systematic comparison with the modelling of fouling layer

In this study, three potential commercial nanofiltration (NF) membranes (MPS-34, SR3D, and HFN-300) were assessed for the treatment of a real process stream of manmade cellulosic fiber (MMCF) industry. Among all, the membrane SR3D had the lowest skin thickness (140 ± 25 nm) and water contact angle (22 ± 3°), and the highest water permeability (4.52 L.m−2.h−1.bar−1). All membranes showed around 85% rejection of sodium sulfate and about 95% rejection of calcium chloride in a synthetic mixture of these salts. In presence of a salt-rich process stream, the best anti-fouling properties were observed with the HFN-300 membrane (92% FRR, 39% FDR, and 8% IFR). During testing with the process stream, permeate flux and solute rejection increased across all membranes with increasing cross-flow rate (CFR) and transmembrane pressure (TMP). To assess membrane effectiveness, a long-term study was conducted with intermittent cleaning at a TMP of 8.3 bar and a CFR of 100 L.h−1. The SR3D membrane exhibited higher permeate flux (average 18.4 L.m−2.h−1), lower COD (56%), and TDS rejection (66%), whereas the HFN-300 membrane showed better TDS rejection (68%) and COD rejection (64%) with moderate permeate flux (10.3 L.m−2.h−1). A semi-empirical model was developed to quantify the flux decline and rejection for the industrial process stream.