Study on the co-catalytic performance and mechanism of MoO2 in oil-contaminated wastewater treated by Fenton system

In the treatment of organic wastewater, Fenton technology often produces iron sludge due to iron circulation obstruction, which inhibits the treatment efficiency and causes secondary pollution to the actual water. In this study, MoO2 was used as a cocatalyst to promote the effective cycling of Fe2+/Fe3+ in the Fe2+/H2O2 system, thus efficiently degrading total petroleum hydrocarbons (TPHs). The superiority of MoO2 as co-catalyst was verified under different reaction conditions, and its mechanism was discussed. The degradation rate of TPHs in the Fe2+/H2O2/MoO2 system (0.069 min−1) was about 14 times that of Fe2+/H2O2 system (0.005 min−1). Compared with the Fe2+/H2O2 system, the Fe2+/H2O2/MoO2 system not only had a wider pH adaptation range, but also could effectively remove TPHs under the interference of co-existing organic and inorganic anions. MoO2 did not change the types of reactive species in Fenton system, but it enhanced the production of reactive oxygen species (ROS) by promoting the Fe2+/Fe3+ cycling in the reaction system, and ·OH was the main reactive species of TPHs degradation.