CDs@Cr₂O₃ catalytic degradation of Orange II based on non-radical pathway

Carbon dots (CDs)-modified Cr₂O₃ (CDs@Cr₂O₃) composites were synthesized by solvothermal process followed by calcination to improve their catalytic performance. The physical and chemical properties of the composites were determined by XRD, SEM, TEM, BET and XPS. With the aid of sodium persulfate, the activity of CDs@Cr₂O₃ to oxidize Orange II by non-radicals was studied under various conditions. The experimental results determined the optimal dosage of PDS to be 0.1 g and the degradation results showed that after 45 min, the degradation rate of Orange II reached to 98.4% with the CDs@Cr₂O₃/PDS/Vis system. The adsorption capacity of CDs@Cr₂O₃ for Orange II was closely related to pH, and this phenomenon is further explained by the isoelectric point. A series of experiments proved that non-free radicals played a crucial role in the oxidation process, in which singlet oxygen (¹O₂), superoxide radical (O₂^•−) and photo-generated holes (h⁺) were determined as the important reactive oxygen species (ROS). In addition, the present study found that increasing dissolved oxygen could promote the reaction and the catalyst maintained good degradation performance after five cycles suggesting its stability.