Fenton-like Oxidation of refractory chemical wastewater using pyrite

Fenton-like reaction technologies are attracting considerable attention due to the high oxidizing ability, especially in the treatment of refractory chemical contaminants. However, some disadvantages in traditional Fenton reagents limited its wide application. In this study, pyrite, a natural iron bearing mineral, was used as a new kind of Fenton-like catalyst in the treatment of textile wastewater. The catalytic activity of pyrite and the parameters influencing the removal of Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD5), such as pyrite dosage, H2O2 concentration, pH, and suspended solids (SS) had been systematically examined. Results showed that pyrite exhibited a high catalytic reactivity over a wide pH value range. At the optimal conditions, a COD removal rate of 70% and an increase in the mass ratio of BOD5/COD (B/C) from 0.25 to 0.56 were achieved in the presence of 9.7 mM H2O2 and 10 g/L, pyrite at initial solution pH value of 9.0. And what's more, a rapid decrease in solution pH and a high level of iron were observed when pyrite was added to the wastewater, probably due to the oxidative dissolution of pyrite. Consequently, Apart from the heterogeneous process, it was found that a homogeneous interaction between ferrous iron and H2O2 in a classical Haber-Weiss mechanism was also occurred. The wonderful reactivity of pyrite makes it be used as catalyst for the oxidative technology to treat the original wastewater without the need to pre-adjust the solution pH.