Fe2O3/coal fly ash Fenton-like catalyst for the elimination of organic pollutants in wastewater: Kinetic, mechanism, and application feasibility

Abstract

Fe2O3/CFA was prepared by loading Fe2O3 on the surface of raw coal fly ash (RCFA), and then used as a Fenton-like catalyst to treat refractory organic wastewater. The characterization results of SEM-EDX, XRD, XPS, XRF, and BET test indicate that Fe2O3 is successfully loaded on the surface of RCFA, while the adsorption performance is not significantly affected. Under optimal treatment conditions of p-nitrophenol (PNP) simulated wastewater (H2O2 dosage = 8 mmol/L, Fe2O3/CFA loading = 6 g/L, pH = 3, and T = 303 K), the removal rate of PNP reaches 97.7 % at 50 min. There exist hydroxyl radicals (·OH), superoxide radicals (∙O2−) and singlet oxygen (1O2) in the Fenton-like system, and ·OH is the primary reactive oxygen species in the removal of PNP·H2O2 dosage, Fe2O3/CFA loading, and pH (i.e., [H+]) show different effects on the generation rate constant of hydroxyl radicals (k·OH), and the corresponding mathematic equation is k∙OH=6.51∙e−640.0T∙[H2O2]1.313∙[Fe2O3/CFA]1.093∙[H+]0.815. The Fenton-like process includes heterogeneous and homogeneous catalytic processes, and it is driven by the synergistic catalysis of multiple metallic elements; Fe and other metallic elements play major and auxiliary roles, respectively. In the advanced treatment of real coking wastewater, the catalytic capacity of Fe2O3/CFA can maintain 91.7 % in its 4th use, and the treatment cost is ¥4.15/ton, which can be decreased by further optimizing the preparation process of Fe2O3/CFA.