Preparation of coal fly ash-based Fenton-like catalyst and its application for the treatment of organic wastewater under microwave assistance

Abstract

In order to realize the high value-added reuse of coal fly ash (CFA), a reusable CFA catalyst (AFA) for a Fenton-like process conducted under microwave (MW) assistance was prepared by H2SO4 impregnation. The optimal AFA preparation conditions included an impregnation time of 60 min, H2SO4 dosage of 0.5 mol/L, impregnation temperature of 303 K, and solid–liquid ratio of 1 g:5 mL. In addition, several AFA critical parameters such as specific surface area, pore size distribution, particle size distribution, surface morphology, relative content, chemical states of the elements on the AFA surface, mass fractions of various AFA oxides, crystal composition, surface chemical bonds, and coordination structure of Si were determined. The dynamic treatment conditions of organic wastewater were optimised using a continuous wastewater treatment system with MW assistance, and the removal efficiency of p-nitrophenol (PNP) exceeded 90% at a hydraulic retention time of 40 min. The AFA was successfully reused three times while retaining a PNP removal efficiency of 90%. The relationship between the PNP removal rate and the utilised treatment conditions was −d[PNP]dt=0.32⋅[H2O2]0.374⋅[AFA]0.337⋅[H+]0.445⋅[PNP]0.475. Furthermore, the AFA surface played the main role and ·OH was the most reactive oxidative radical. Hence, real coking wastewater can be effectively treated by the AFA-catalysed Fenton-like process under MW assistance.