Oxidation-precipitation of magnetic Fe3O4/AC nanocomposite as a heterogeneous catalyst for electro-Fenton treatment

The oxidation-precipitation method was used for the synthesis of Fe3O4/AC. The characterization of the catalyst was accomplished by XRD, FT-IR, FE-SEM, BET, and VSM techniques. The obtained results indicated that magnetite nanoparticles were successfully prepared with cubic spinel structures and uniform distribution on the surface of activated carbon by the oxidation-precipitation method. The effect of operating parameters was evaluated to determine the optimum operating condition for the electro-Fenton (EF) removal of catechol as a phenolic pollutant model. At the optimum operating conditions (pH 3, Fe3O4/AC: 0.9 g L−1, Catechol: 8.0 × 10−4 mol L−1 at I: 120 mA), the catechol and COD removal reached 98.2 and 76.1% in 120 min, respectively. Only 2.1% of ferrous and 3.44% of ferric ions were leached into the solution. Regarding the results from utilization of oxidant scavengers (isopropanol and BQ), it can be inferred that hydroxyl radical (responsible for 57% catechol removal) and superoxide anion radical (responsible for 40% catechol removal) is the main oxidants in acidic (pH 3) and basic (pH 10) conditions, respectively. The kinetics of EF removal of catechol was studied and the rate constant for the pseudo-first-order kinetic model was found to be 3.37 × 10−2min−1 (R2 = 0.9924). The GC-MS analysis was carried out to detect the intermediate products and a possible degradation mechanism was proposed. The reusability of Fe3O4/AC was examined for six cycles. It can be concluded that Fe3O4/AC is an applicable ultimate catalyst for EF removal of organic pollutants.