Upcycling polyvinyl chloride waste into highly efficient amine-functionalized nanofiber membrane adsorbent through the dissolution-modification-reforming process

Abstract

Polyvinyl chloride (PVC) waste recycling is a challenging task and there is a great lack of convenient, feasible, and effective methods. In this work, a dissolution-modification-reforming process was proposed to upcycle PVC into highly efficient adsorbents (polyethylenimine-crosslinked PVC nanofiber membranes (PEI/PVC NFMs)). The effect of PEI to PVC mass ratio on the preparation of PEI/PVC NFMs was estimated. The adsorption performance of azo dyes on PEI/PVC NFMs was evaluated using Reactive Black 5 (RB5). The acid/alkali resistance of PEI/PVC NFM and its adsorption potential for various ionic pollutants were also investigated. Here are the results: The PEI/PVC NFMs exhibited high RB5 uptake within pH 2 to 8. The amine groups content in PEI/PVC NFM increased with increasing of PEI to PVC mass ratio, resulting in faster adsorption rates and higher adsorption capacity. With the mass ratio of PEI to PVC increased from 0.5:1.0 to 2.0:1.0, the adsorption equilibrium time reduced from 480 to 120 min, while the maximum RB5 uptake increased from 314.5 to 1036.7 mg/g. The adsorption isotherms and thermodynamic analysis revealed that physisorption dominated the adsorption process. The PEI/PVC NFM also exhibited good adsorption potential for various ionic pollutants, including per-/poly-fluoroalkyl substances (PFAS) and heavy metals (Pb2+, H2AsO4−, Co2+, and Ni2+). The 30-d acid/alkali resistance test confirmed that the PEI/PVC NFM has better stability at higher pH conditions. The PEI/PVC NFM exhibited good recyclability in azo dye wastewater treatment. In conclusion, this study demonstrates that the dissolution-modification-reforming process is a viable route for PVC waste upcycling. This pathway allows the conversion of PVC waste into highly efficient adsorbents for the elimination of ionic pollutants from water. © 2023