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

Abstract

In this study, the catalytic performance of natural pyrite was increased through thermal activation. The degradation efficacy of the PY-250/H2O2 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 H2O2, and the apparent rate constant (kobs) was 5.22-fold in comparison with the pyrite/H2O2 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/H2O2 system included •OH, 1O2, and •O2-, of which •OH and 1O2 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 H2O2, 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.