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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 MgCl 2. 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. [Display omitted] • Positively charged NF membrane was developed through surfactant post-treatment. • IP built dense PA layer was optimized by monomers concentration adjustment. • CTAB and SDS endowed superior positively and negatively charged surfaces. • The surfactant layer offers a superior NF performance. • CTAB attached TFC membrane owns excellent heavy metals removal ability and stability. [ABSTRACT FROM AUTHOR]

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 MgCl 2. 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. [Display omitted] • Positively charged NF membrane was developed through surfactant post-treatment. • IP built dense PA layer was optimized by monomers concentration adjustment. • CTAB and SDS endowed superior positively and negatively charged surfaces. • The surfactant layer offers a superior NF performance. • CTAB attached TFC membrane owns excellent heavy metals removal ability and stability. [ABSTRACT FROM AUTHOR]

A green method for safety drinking water production was proposed in this study by the development of a positively charged nanofiltration (PNF) membrane composed of two different functional layers. Glycosyl layer was fabricated through interfacial polymerization in which the performances of sucrose doped NF membrane was superior to the glucose and raffinose doped membranes, which were further enhanced by alkali treatment. Sucrose (0.8 wt%) and NaOH (0.05 mol‧L−1) benefit the formation of higher porosity and better hydrophilicity and offer a high pure water flux (13.5 L m−2 h−1·bar−1) and Na 2 SO 4 rejection (99.3%). Then, the PNF membrane was acquired by coating polyethyleneimine (PEI) on the sucrose-polyamide layer. The concentration of PEI and grafting time were both studied and the optimal membrane showed an excellent performance for heavy metals removal. The as-developed membrane has found its potential application in drinking water purification which gave 90% rejection for heavy metals and the permeance reached to 7.4 L m−2 h−1·bar−1. With the proposed method, the trace elements were retained partially which was beneficial to the human body and the toxic metals were kept within the limits. Image 1 • Positive charged NF membrane with dual functional layers was proposed. • Glucose, sucrose and raffinose were used to form negatively charged layer. • Sucrose and NaOH offer higher porosity, better hydrophilicity and separation ability. • PEI coated TFC membrane has excellent heavy metals removal ability and stability. • The positively charged membrane exhibited well in drinking water purification. [ABSTRACT FROM AUTHOR]