Self-healable poly-(acrylic acid)@Fe/Ni hybrid hydrogel membrane for Cr(VI) removal from industrial wastewater

Water contamination is increasing globally by heavy metals, dyes, and cyanides day by day. Heavy metals are very toxic even if present in a small amount in water. Here, we have synthesized a novel type of self-healable, ultra-thin with high mechanical strength, and pH-responsive poly-(acrylic acid)@Fe/Ni (PAA@Fe/Ni) hybrid hydrogel membrane using filter paper as a substrate. Acrylic acid was polymerized on the surface and in pores of the filter paper by free radical addition polymerization reaction using NMBA as a cross-linker, iron ions as an accelerant, and persulfate radicals as initiator. The iron ions were subsequently converted to metal particles by coating with nickel particles to enhance their stability and act as an antifouling agent. The membrane was characterized by FTIR, SEM, EDX, and AFM techniques. The abundant carboxylic acid (-COOH) groups and iron ions present inside the polymer network provide self-healing ability to the membrane. The pore size of the filter paper was reduced from 2.5 to 1.04 mu m and thus improving the rejection capability of the membrane. The results demonstrated that the membrane is efficient enough for the complete rejection of Cr(VI) from model water and industrial wastewater under different environmental stimuli (pH and concentration) up to 100 ppm. The self-healing behavior, ultra-thin with high mechanical stability, and responsive nature of the PAA@Fe/Ni hybrid hydrogel membrane are the significantly advanced features of the synthesized membrane.