A feasible approach for azo dye degradation using natural magnetite in heterogeneous Fenton oxidation

Azo dyes, which are widely used in the textile industry, are typical toxic and refractory pollutants in wastewater. Heterogeneous Fenton oxidation is effective in degrading organic compounds; however, it may induce Feleaching. Therefore, it is necessary to find efficient, cheap, and natural iron mineral catalysts for heterogeneous Fenton oxidation. This work aimed to investigate the removal of the representative azo dye reactive yellow 3 (RY3) by iron mineral/H2O2 oxidation. Compared with hematite and pyrite, magnetite showed superior RY3 degradation efficiency via heterogeneous Fenton oxidation. The optimum parameters for degradation of 50 mg/L RY3 by magnetite/H2O2 were 0.2 g/L magnetite, 0.5 mM H2O2, and pH 3.5. Under the optimum parameters, RY3 was almost completely degraded within 40 min. Through free radical trapping experiments, hydroxyl radicals (.OH) were identified as the dominant reactive radical species for RY3 degradation by magnetite/H2O2 oxidation.