Enhanced removal efficiency of heavy metal ions by assembling phytic acid on polyamide nanofiltration membrane

The water pollution caused by heavy metals is bringing serious damage to public health and environment, and significant efforts have been devoted to explore advanced materials and technologies for eliminating toxic metal ions more efficiently. Herein, a phytic acid (PA)-incorporated polyamide thin-film composite nanofiltration (NF) membrane is constructed though traditional interfacial polymerization and electrostatic assembly of PA with polyethyleneimine. Owing to the high negative charges of PA, the resultant NF membrane exhibits ultrahigh binding affinity for heavy metals cations, and is highly capable of removing heavy metal ions from aqueous solution. As a result, the PA-functionalized NF membrane can reduce Cd2+ and Pb2+ concentrations from 500 ppm to the ultralow level of ~0 and 5 ppb, and achieve record-breaking remove rates of 100.000% for Cd2+ and 99.999% for Pb2+. Additionally, the as-prepared NF membrane also delivers excellent long-term stability in continuous 120-h operation, and can be easily regenerated and reused without remarkable fading of the initial Cd2+ removal rate even after six filtration cycles. This work demonstrates the potential usage of the PA-functionalized NF membrane for serving as a promising platform to eliminate heavy metal ions in waste water.