Preparation of PrFexCo1–xO3/Mt catalyst and study on degradation of 2-hydroxybenzoic acid wastewater by catalytic wet peroxide oxidation

Abstract

In this study, the perovskite nanocomposite PrFexCo1–xO3(Pr(S)) was successfully synthesized by the sol–gel method; PrFexCo1–xO3/Al-pillared montmorillonite (Pr(S)/Mt) catalysts were prepared by impregnation (D) method and solid-melting (G) method, respectively, with Pr(S) as the active component and Al-pillared montmorillonite as the carrier. The catalysts were applied to treat the 2-hydroxybenzoic acid (2-HA)-simulated wastewater by catalytic wet peroxide oxidation (CWPO) technique, and the chemical oxygen demand (COD) removal rate and the 2-HA degradation rate were used as indicators to evaluate the catalytic performance. The results of the experiment indicated that the solid-melting method was more conducive to preparing the catalyst when the Co/Fe molar ratio of 7:3 and the optimal structural properties of the catalysts were achieved. The influence of operating parameters, including reaction temperature, catalyst dosage, H2O2 dosage, pH, and initial 2-HA concentration, were optimized for the degradation of 2-HA by CWPO. The results showed that 97.64% of 2-HA degradation and 75.23% of COD removal rate were achieved under more suitable experimental conditions. In addition, after the catalyst was used five times, the degradation rate of 2-HA could still reach 76.93%, which implied the high stability and reusability of the catalyst. The high catalytic activity of the catalyst was due to the doping of Co into PrFeO3, which could promote the generation of HO·, and the high stability could be attributed to the loading of Pr(S) onto Al–Mt, which reduced the leaching of reactive metals. The study of reaction mechanism and kinetics showed that the whole degradation process conformed to the pseudo-first-order kinetic equation, and the Langmuir–Hinshelwood method was applied to demonstrate that catalysis was dominant in the degradation process.