Upcycling of plastic waste into polymeric membranes for photocatalytic degradation of diclofenac sodium: mechanistic and DFT insights

Abstract

The pharmacologic anti-inflammatory drug diclofenac sodium (DCF) is widely used for pain management across various medical treatments and discarded into waterways without proper treatment, polluting them. Conventional methods for degrading DCF have drawbacks, including hydrophobicity, limited thermal stability, and insufficient mechanical strength. In this work, polyurethane (PU) has been extracted from waste plastic and modified by MnO₂ NPs to fabricate a polyurethane/MnO₂ (PU/MnO₂) modified polymeric membrane (MPM). The photocatalytic degradation of DCF was studied using UV-visible spectroscopy. The optimum conditions were as follows: a solution pH of 4, an H₂O₂ concentration of 1 mL, a DCF solution concentration of 5 mg L⁻¹, and MnO₂ NPs (0.4 g) incorporated into a polymeric membrane; under these conditions, 95% degradation of DCF was achieved within 240 min. Additionally, PMs exhibit antioxidant properties due to their ability to scavenge DPPH (2,2-diphenyl-1-picrylhydrazyl) free radicals. DFT (density functional theory) calculations also supported the degradation study by illustrating the interaction between the MPM and DCF. Seed germination of Vigna radiata was done using treated water with a modified polymeric membrane, which showed a positive growth response. This study provides a novel method for developing a polymeric membrane from waste plastic, which can then be used for the photocatalytic degradation of DCF in water sources.