Solid peroxides in Fenton-like reactions at near neutral pHs: Superior performance of MgO on the accelerated reduction of ferric species.

Fenton-like reactions at near neutral pHs are limited by the slow reduction of ferric species. Enhancing generation of from solid peroxides is a promising strategy to accelerate the rate-limiting step. Herein, the HO release and Fenton-like reactions of four solid peroxides, MgO, CaO, ZnO and urea hydrogen peroxide (UHP), were investigated. Results indicated that UHP can release HO instantly and show a similar behavior as HO in the Fenton-like reactions. MgO released HO quickly in phosphate buffered solutions, which was comparable to CaO but faster than ZnO. Metal peroxides induced higher initial phenol degradation rates than UHP and HO when the same theoretic HO dosages and Fe(III)-EDTA were used. MgO displayed a superior performance for phenol degradation at pH 5, resulting in more than 93% phenol reduction at 1.5 h. According to kinetic analyses, the generation rate of in the MgO system was 18 and 3.4 times higher than those in ZnO and CaO systems, respectively. The addition of MgO significantly promoted HO based Fenton-like reactions by increasing production of , and the mixture of MgO and HO had an improved utilization efficiency of active oxygen than the MgO system. The findings suggested the critical roles of metal peroxides in favoring Fenton-like reactions and inspired strategies to simultaneously accelerate Fenton-like reactions and improve utilization efficiency of active oxygen.