Green multifunctional PVA composite hydrogel-membrane for the efficient purification of emulsified oil wastewater containing Pb2+ ions

To date, most existing engineering materials have difficulty simultaneously separating oil/water and removing heavy metals from complex oily wastewater. In response to this challenge, a novel multifunctional composite hydrogel membrane (named PVA-CS-LDHs) was fabricated by incorporating chitosan (CS) and nanohydrotalcite (LDHs) into a polyvinyl alcohol (PVA) hydrogel. This material was developed using an easy yet versatile strategy of freezing and salting-out, which can enable the formation of a PVA-CS-LDH hydrogel membrane in one step and endow the PVA-CS-LDHs with high strength, excellent stretchability, favourable shape recoverability, and an ideal 3D microstructure. The PVA-CS-LDH membrane can purify emulsified oil and metal ions simultaneously with a separation efficiency of 99.89 % for emulsified oil and a removal efficiency of 97.44 % for Pb2+ ions. Additionally, the high-efficiency, multifunctional, high-antifouling and eco-friendly properties of the PVA-CS-LDH membrane make it a promising hydrogel material for both emulsified oil separation and heavy metal ion removal. Thus, this material provides critical application potential that can address scientific and technological challenges in complex oily wastewater purification.