Activation of peroxydisulfate over NiO microparticles for the degradation of bisphenol A: Mechanism insights, biotoxicity assessment and application to real wastewater treatment

The development of efficient and stable catalysts for advanced oxidation processes (AOPs) is of increasing interest for water purification. In this study, commercially available NiO microparticles were employed as an effective catalyst for the activation of peroxydisulfate (PDS) to degrade bisphenol A (BPA). Comprehensive physicochemical characterization confirmed that NiO possessed morphology of aggregated microparticles, coexisting Ni²⁺/Ni³⁺ oxidation states, and abundant surface oxygen vacancies, which are favorable for activating PDS. Under optimized conditions, the NiO/PDS system exhibited a degradation efficiency of 93.2% and a mineralization rate of 82.96%. Quenching experiments and electron paramagnetic resonance (EPR) analysis revealed that both radical and non-radical pathways were involved in the degradation process, where radical pathway played a minor role and non-radical pathway played a dominant role. The system demonstrated sufficient resistance to anion interference, pH variation, and humic acid presence, and exhibited a selective degradation for the target pollutant BPA. Furthermore, application to real pharmaceutical wastewater further confirmed the practical applicability of the NiO/PDS system, and a bio-toxicity assessment using the Ecological Structure Activity Relationships (ECOSAR) model predicted a substantial reduction in ecological risk of BPA solution after the treatment by the system.