Insight into CaO₂-based Fenton and Fenton-like systems: strategy for CaO₂-based oxidation of organic contaminants

This study conducted a comparison of the CaO₂-based Fenton (CaO₂/Fe(II)) and Fenton-like (CaO₂/Fe(III)) systems on their benzene degradation performance. The H₂O₂, Fe(II), Fe(III), and HO^● variations were investigated during the benzene degradation. Although benzene has been totally removed in the two systems, the variation patterns of the investigated parameters were different, leading to the different benzene degradation patterns. In terms of the Fe(II)/Fe(III) conversion, the CaO₂/Fe(II) and CaO₂/Fe(III) systems were actually inseparable and had the inherent mechanism relationships. For the CaO₂/Fe(III) system, the initial Fe(III) must be converted to Fe(II), and then the consequent Fenton reaction could be later developed with the regenerated Fe(II). Moreover, some benzene degradation intermediates could have the ability to facilitate the transformation of the Fe(III) to Fe(II) without the classic H₂O₂-associated propagation reactions. By varying the Fe(II) dosing method, an effective degradation strategy has been developed to take advantage of the two CaO₂-based oxidation systems. The proposed strategy was further successfully tested in TCE degradation, therefore extending the potential for the application of this technique.