Efficient bimetallic activation of sulfite by CoFe-LDH for bisphenol A removal: Critical role of Co/Fe ratio on ROS generation

The sulfite (S(IV))-based advanced oxidation process is an emerging approach for the treatment of phenolic pollution. In this study, CoFe-layered double hydroxides (CoFe-LDHs), showing superior physicochemical properties as catalysts, were applied to activate S(IV) for bisphenol A (BPA) degradation. The results show that the Co/Fe molar ratios play a crucial role in regulating the physicochemical properties, degradation capacity, and activation mechanism of the catalysts, with Co3Fe1-LDH exhibiting the best performance in BPA degradation. The degradation of BPA is significantly influenced by pH and dissolved oxygen, and proceeds through bimetallic synergism and both radical and non-radical pathways. However, with increasing Co/Fe ratio, SO4•− gradually assumes a more prominent role in degradation by the system, and the contributions from high-valent metals and HO• gradually diminish. Additionally, the system brought about a substantial reduction in toxicity after degradation, and the catalyst demonstrated promise in consecutive recycling experiments, the degradation of other organics, and tests in actual water bodies.