Surfactants attached thin film composite (TFC) nanofiltration (NF) membrane via intermolecular interaction for heavy metals removal

Heavy metals are well-known pollutant in the water body, which can threaten our health in various ways. Since size exclusion and electrostatic repulsion play a significant role in heavy metals removal for membrane technology, hereon, a positively charged nanofiltration membrane with a dense polyamide (PA) layer and a surfactant functionalized layer (SFL) was successfully developed. The optimization of the PA layer was achieved by adjusting the concentration of piperazine (PIP) and trimesoyl chloride (TMC) during interfacial polymerization and the thin film composite (TFC) membrane formed by 0.4% (w/v) PIP and 0.01% (w/v) TMC was selected for further study due to its gratifying performance. Then, the membrane was developed by attaching surfactants in which cetyl trimethyl ammonium bromide (CTAB) endowed a superior positively charged surface whereas sodium dodecyl sulfate (SDS) intensified negative charge compared to the original membranes. Furthermore, the SFL attached membrane was successfully obtained by attaching CTAB with various concentration and grafting time. The feed concentration of all metal ions and salts adopted for evaluating NF performances were 500 mg‧L−1. The best performance showed a high water permeability of 21.5 ± 0.6 L‧m−2‧h−1‧bar−1 and 96.6 ± 1.4% rejection for MgCl2. Overall, the as-developed SFL attached membrane has found its potential application in heavy metal removal in which the separation efficiency was over 98% against Zn2+, Ni2+, 96%–98% against Cu2+, >94% against Ca2+ and >85% against Pb2+ with a high efficiency of water reclamation simultaneously.