Optimization of Catalytic Properties of Natural Pyrite by Calcination Heat Treatment: Mechanism and Efficacy of Fenton-like Reaction for Degradation of Organic Pollutants

In this study, the catalytic performance of natural pyrite was increased through thermal activation. The degradation efficacy of the PY-250/H 2 O 2 system on Rhodamine B (RhB) was systematically investigated. The results showed that the degradation rate of RhB at 50 mg·L –1 reached 96.4% in 2 min under the combined effect of 0.3 g·L –1 PY-250 and 2.0 mM H 2 O 2, and the apparent rate constant ( k obs ) was 5.22-fold in comparison with the pyrite/H 2 O 2 system. The PY-250 exhibited excellent adaptability under a broad pH range and effectively mitigated interference from anions and humic acids. Radical scavenging experiments revealed that the reactive oxygen species (ROS) generated within the PY-250/H 2 O 2 system included • OH, 1 O 2, and • O 2 –, of which • OH and 1 O 2 played a primary role in RhB degradation. The excellent catalytic activity of PY-250 is intimately associated with two factors: first, the thermal activation formed surface sulfate, which caused ferrous ions to be induced to dissolve, facilitated the activation of H 2 O 2, and promoted the degradation of RhB via ROS. Second, thermal activation treatment could increase the sulfur vacancies (SVs) on the pyrite, which promotes the cycling of Fe(III)/Fe(II), significantly delaying the deactivation of the catalyst. Therefore, this study provides new material options for the development of green low-cost catalysts to promote the widespread application of Fenton-like catalytic reactions in practical wastewater treatment.