Comparative studies on catalytic mechanisms for natural chalcopyrite-induced Fenton oxidation: Effect of chalcopyrite type

•A systematic comparative study of p- and n-type chalcopyrite (Cpy A and Cpy B) as the Fenton catalysts was carried out.•The degradation of AO7 was significantly enhanced by Cpy B/H2O2 reaction, rather than Cpy A.•The releasing amount of metal ions was the main reason for the difference of degradation effect.•The relative contribution of the homogeneous vs. heterogeneous process for AO7 removal was calculated (80% vs. 20%). The type of chalcopyrite plays a key role in determining its physicochemical properties. In this study, we present a systematic comparative study on the use of p- and n-type chalcopyrite (Cpy A and Cpy B, respectively) as Fenton catalysts for wastewater treatment. Experimental results showed that 60% of AO7 removal could be achieved in 30 min at a natural pH when H2O2 was activated by Cpy A. The removal rate could be further enhanced by up to 100% within 5 min using Cpy B as the catalyst. This is because Cpy B released far more Cu+ and Fe2+ ions, and less Cu2+ after being washed, and then activated H2O2 to produce more ·OH radicals (main active species). On the other hand, the excess copper ions released from Cpy A could react with AO7 to generate an intermediate product that would negatively affect the degradation process. Finally, the relative contribution of the homogeneous vs. heterogeneous process was calculated. Although only about 20% of the contribution for AO7 degradation was provided by heterogeneous processes in both systems, the time for full removal could be obviously reduced to 5 min from 20 min (homogeneous process) in the Cpy B/H2O2 system.