Zr-Zn bimetallic organic frameworks functionalized PTFE composite membranes with effective removal of Cr(VI) from aqueous solutions

Accelerated industrial expansion has led to significant wastewater pollution, with effluent containing the toxic heavy metal Cr(VI) posing severe threats to ecosystems and human health. The combination of metal-organic frameworks (MOFs) and membrane separation techniques offers promising solutions for pollutant removal. This study developed a polytetrafluoroethylene (PTFE)-based composite membrane for effective Cr(VI) removal from aqueous solutions. This membrane was prepared through the in-situ synthesis of zinc-zirconium bimetallic MOFs on a PTFE membrane that had been modified with L-DOPA/PEI. The composite membrane demonstrated optimal Cr(VI) adsorption at a Zr:Zn molar ratio of 1:4, under conditions of 45 °C and pH = 2, with a maximum adsorption capacity of 335.1 mg/g. The adsorption process of Cr(VI) onto the composite membrane adhered to both the pseudo-second-order kinetic model and the Freundlich adsorption isotherm. Thermodynamic analyses confirmed a spontaneous, endothermic process. The composite membrane, with its excellent adsorption capacity, filtration performance, and recyclability, stands out as a highly effective material for the removal of Cr(VI) from aqueous solutions. Furthermore, it addresses the issues of aggregation, difficulty in separation, and the recycling challenges associated with powder-like MOFs, demonstrating significant potential for practical applications.