Novel high-flux positively charged composite membrane incorporating titanium-based MOFs for heavy metal removal

•A novel MOFs/PEI/TMA composite membrane is developed for heavy metal removal.•NH2-MIL-125(Ti) provided preferential water channels to improve permeability.•New and facile cross-linking process provides strong positive charge surface.•The interaction between NH2 and PEI/TMA system increases the stability of MOFs.•Nanocomposite membrane has 369% higher flux than the pristine membrane. In this study, a novel positively charged nanofiltration (NF) membrane was fabricated by incorporating metal–organic frameworks (MOFs) into polyethyleneimine (PEI) and trimesic acid (TMA) cross-linking system. NH2-MIL-125(Ti) provides preferential water channels to improve the permeability of the composite membrane. The effects of NH2-MIL-125(Ti) loading on the membrane morphology, structure and properties were investigated by ATR-FTIR, SEM, EDS, AFM, Zeta potential measurements, etc. Studies have shown that the optimal preparation condition was determined at 0.010 wt% NH2-MIL-125(Ti) loading. The prepared membrane exhibited a high permeability of 12.2 L·m−2·h−1·bar−1 and a NiCl2 rejection of 90.9%. Compared with the pristine composite membrane, the membrane with appropriate amount of NH2-MIL-125(Ti) greatly improved the permeability (369.2%). The combination of NH2-MIL-125(Ti) and PEI/TMA cross-linking system has positive significance for the heavy metal wastewater treatment industry.