Degradation of bisphenol S by peroxymonosulfate activation through monodispersed CoFe₂O₄ nanoparticles anchored on natural palygorskite

Bisphenol S (BPS) has been detected frequently in water bodies, which poses a serious threat to human health and the environment. The sulfate radical-based advanced oxidation process is considered as a promising water purification technology by activating peroxymonosulfate (PMS). However, a catalyst with low metal leaching rate and high effective catalytic ability is needed to activate PMS. In this study, natural clay of palygorskite (PAL) was used to mediate monodispersed CoFe₂O₄ nanoparticles to degrade BPS by PMS activation. The monodispersed CoFe₂O₄ nanoparticles were distributed and anchored on the surface of PAL, which caused the 16%-CoFe₂O₄@PAL (16%-CFO@PAL) composite expose more reaction sites, thus exhibiting excellent catalytic performance. A satisfactory BPS removal rate (> 99%) was obtained by introducing 50 mg L^-1 16%-CFO@PAL and 0.16 mM PMS. The interaction mechanism between CoFe₂O₄ nanoparticles and PAL was discussed. The Al-O-Fe bond between CoFe₂O₄ nanoparticles and PAL endowed the 16%-CFO@PAL composite with low metal leaching property, high stability and reusability. SO₄^·- and ¹O₂ played a dominant role in the degradation of BPS. The generation mechanism of reactive species was proposed. The influences of various degradation parameters (e.g., catalyst dosage, PMS concentration, initial solution pH, and BPS concentration) and water constituents (e.g., inorganic anions and NOM) on the degradation of BPS were investigated. Based on the identified intermediates and density functional theory (DFT) calculations, the possible degradation pathways of BPS were discussed. This study provides a new idea for the preparation of high-efficiency natural clay-based PMS catalysts for water purification.