Efficient removal of Cr(VI) from wastewater by composite adsorptive membrane modified with polyethyleneimine (PEI)

The development of an efficient and economical method to remove the toxic Cr(VI) from water is a global challenge. This study developed a new composite adsorptive membrane by combining polyacrylonitrile (PAN) as a substrate with crosslinked polyethyleneimine (PEI) to efficiently remove Cr(VI) from wastewater. After optimizing the preparation conditions of the material, the Cr(VI) removal by PEI/GMA@PAN was investigated using batch adsorption and longer-term filtration experiments. The composite adsorptive membrane exhibited a high adsorption capacity, reaching a maximum of 89.16 mg/g, along with fast adsorption kinetics that achieved equilibrium within 100 min for Cr(VI) removal. Even in the presence of coexisting ions, the PEI/GMA@PAN membrane maintained a high efficiency in removing Cr(VI). The removal mechanism mainly relied on electrostatic interactions and the reduction of Cr(VI) to Cr(III). Notably, long-term filtration experiments substantiated the membrane's effectiveness in removing Cr(VI) from synthetic wastewater, with an impressive treatment volume of 342 L/m2. The optimized PEI/GMA@PAN membrane also demonstrated low PEI leaching across a wide pH range and the potential for re-utilization through four-round cycles, underscoring its promising applicability in wastewater treatment. Therefore, the newly synthesized composite membranes show potential for the removal of Cr(VI) from wastewater.