Boosting Peroxymonosulfate Activation via Sludge-Based Catalyst for the Degradation of BPA: Mechanism Analysis of Acid Etching

The increasing production of residual sludge has heightened interest in its resource utilization. In this study, municipal sewage sludge was pretreated with HCl-HF-HCl mixed acid etching and then pyrolyzed to prepare a sludge-based catalyst (MSF). The effects of acid etching on the physicochemical properties of the catalyst and its ability to activate peroxymonosulfate (PMS) for degrading bisphenol A (BPA) were systematically investigated. Results showed that acid etching removed inorganic impurities, optimized the pore structure, and increased the specific surface area to 248.06 m2/g. It also exposed more carbon defects and active sites, while enhancing surface oxygen-containing functional groups and graphitic nitrogen. The MSF/PMS system achieved nearly 100% BPA degradation within 90 min, far exceeding the control sample (MS). Quenching experiments and electron paramagnetic resonance (EPR) analyses confirmed that singlet oxygen (1O2) played a dominant role, accompanied by an electron transfer-mediated nonradical pathway. Electrochemical tests further demonstrated the enhanced electron conduction capability of MSF, which facilitated PMS activation. Moreover, MSF exhibited high adaptability and stability over a broad pH range (3–11) and in real water matrices, demonstrating great potential for practical applications. This study provides a theoretical foundation and technical support for sludge resource recovery and the development of efficient catalysts.