Producing OH, SO4− and O2− in heterogeneous Fenton reaction induced by Fe3O4-modified schwertmannite

Heterogeneous Fenton has become a promising economical and environmentally-friendly method for water treatment, however, the production of abundant radical resources (e.g., O 2 − , OH) are oftentimes limited by finite Fe 2+ species to activate H 2 O 2 . Therefore, development of a new iron-bearing solid modified with diverse functional groups for generating a large of radicals in heterogeneous Fenton is significance. Here, we constructed a Fe 3 O 4 -modified schwertmannite (Fe 3 O 4 /Sch) catalyst to activate H 2 O 2 , SO 4 2− and O 2 to produce three kinds of radicals in heterogeneous Fenton reaction. Specifically, Fe 3 O 4 /Sch catalyst was synthesized to improve its surface properties such as the contents of surface Fe 2+ species as H 2 O 2 or O 2 activators to produce OH or O 2 − , the SO 4 2− of Sch surface as SO 4 − precursor, and electron transfer between Fe 3+ and Fe 2+ . Degradation rate of ciprofloxacin (CIP) for 6 min was up to 97% in Fe 3 O 4 /Sch-H 2 O 2 system, which was higher than that in Sch-H 2 O 2 or Fe 3 O 4 -H 2 O 2 . After four successive cyclic experiments, degradation rate of CIP was still achieved 97% within 10 min in Fe 3 O 4 /Sch-H 2 O 2 system. The formation pathways of the relevant active radicals and the degradation pathways of CIP were also proposed by theoretically calculated and LC-MS data. This finding has not only developed an efficient heterogeneous Fenton catalyst, but also given a new idea of SO 4 − generation by modified iron oxyhydroxysulfate mineral for application of heterogeneous Fenton technology.