Degradation of bisphenol A via the electro–Fenton process using nanostructured carbon-metal oxide anodes: Intermediates and reaction mechanisms study

The removal of the bisphenol A (BPA) from sulphate-rich wastewater has been investigated using an electro-Fenton oxidation system with metal-oxide carbon nanostructured anode. The process produces highly oxidizing species, including hydroxyl radicals on the anode surface and bulk solution via an electrochemically monitored Fenton reaction. The focus of this research is the detection of BPA intermediates and the prediction of the BPA degradation mechanism during the electro-Fenton process using the SnO2-MWCNT nanostructured anode. In accordance to detected reactive oxygen species, BPA intermediates, and their respective peak area profiles, two primary degradation pathways can be defined. Whether direct cleavage of BPA precedes hydroxylation, oxidation, and dealkylation, or vice versa, the resulting products consist of catechols, dicatechols, quinones, aldehydes, carboxylic acids, and ultimately carbon dioxide and water. To ensure a comprehensive understanding, the impact of applied current, catalyst concentration, and treatment duration on degradation and mineralization efficiency, as well as degradation kinetics, was investigated. The degradation of BPA was found to follow pseudo-first-order reaction kinetics. The results showed that the degradation of BPA was attributed to the co-action of electro-Fenton oxidation and electrochemical oxidation. This study confirms the eco-friendly nature of the electro-Fenton process by demonstrating the toxicity of intermediaries formed during BPA treatment.