Roles of hydroxyl and carbonate radicals in bisphenol a degradation via a nanoscale zero-valent iron/percarbonate system: influencing factors and mechanisms

Abstract

In this work, nanoscale-zero-valent iron (nZVI) was applied to activate sodium percarbonate (SPC) to eliminate bisphenol A (BPA), which poses a risk to ecological and human health as a typical endocrine disruptor. The influence of nZVI loading, SPC dosing, initial pH, and the presence of inorganic anions (including Cl⁻, HPO₄²⁻, NO₃⁻ and NO₂⁻) and humic acid on BPA removal by the nZVI/SPC system were investigated. Based on the scavenger test results, ˙OH and CO₃˙⁻ participated in the degradation of BPA, and ˙OH was illustrated to be the dominant radical. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis suggested that surface iron oxide generation, electron transfer and Fe²⁺ release were the main processes of the SPC activation by nZVI. Moreover, BPA transformation products were detected by LC-MS allowing the proposal of a possible degradation pathway of BPA. Along with the degradation of the parent compound BPA, the total organic carbon (TOC) gradually decreased, while the bio-toxicity increased at the initial stage of the reaction (0–3 min) and then decreased to a lower level rapidly at 20 min. Overall, this study evidenced the feasibility of the nZVI/SPC system to efficiently degrade BPA, broadening the applications of nZVI in wastewater treatment.