Porous Carbon-Coupled Co-ZnO Heterojunction with Synergistic Photocatalytic Activity for Visible-Light-Driven Bisphenol A Degradation

The persistent occurrence of bisphenol A (BPA) in aquatic environments poses severe endocrine-disrupting risks, demanding innovative and sustainable remediation approaches. Semiconductor-based photocatalysis has gained significant attention as a green and cost-effective strategy for eliminating such endocrinedisrupting chemicals (EDCs) from wastewater. This study introduces a novel CCAC/Co-ZnO heterojunction nanocomposite, synthesized hydrothermally by integrating cobalt-doped zinc oxide nanoparticles with porous activated carbon derived from Croton caudatus biomass. The biomass-derived carbon component was incorporated to broaden visible-light absorption, minimize charge carrier recombination, and maximize surface reactivity. Physicochemical characterization through XRD, SEM, HR-TEM, XPS, BET, and UV-Vis DRS confirmed the successful formation of the nanostructure with desirable photocatalytic properties. Under optimized conditions, the nanocomposite achieved 99.67 % BPA removal within 60 minutes of visible-light irradiation, following pseudo-first-order kinetics (kap = 0.055 min⁻¹, t₁/₂ = 12.6 min). Radical trapping experiments identified hydroxyl radicals (•OH) and photogenerated holes (h⁺) as the predominant reactive oxygen species driving BPA mineralization. LC-MS analysis enabled identification of transformation intermediates and proposal of a stepwise degradation pathway. Cyclic stability assessments confirmed 77.63 % retained efficiency over five successive runs, demonstrating outstanding photostability and recyclability. DFT calculations further elucidated the electronic structure and charge redistribution mechanisms at the heterojunction interface, providing deeper mechanistic understanding of the enhanced photocatalytic activity. These findings establish a viable pathway for developing biomass-derived, solar-light-responsive photocatalysts toward sustainable environmental remediation.