Alkali-Fused Coal Gasification Fine Slag for Simulated Phenolic Wastewater Treatment: Adsorption–Oxidation Performance and Mechanistic Investigation

Abstract

Coal gasification fine slag (CGFS) is a large amount of industrial solid waste produced by the coal chemical process. Phenol in coking wastewater is a kind of refractory and highly toxic organic pollutants. In order to solve the two types of environmental problems simultaneously, porous active materials (CGFS-AFAC-800) were prepared by the NaOH alkali fusion method at 800 °C using CGFS as the raw material and applied to the efficient removal of phenol in simulated coking wastewater. The key adsorption parameters were optimized by the single factor experiment and orthogonal experiment. The adsorption performance and mechanism were studied by adsorption kinetics, isothermal adsorption, and adsorption thermodynamics. The results showed that the optimum adsorption conditions were as follows: activated material dosage 10 g·L–1, adsorption time 60 min, temperature 40 °C, initial pH = 3, H2O2 dosage 5 mM, and the removal rate of phenol was up to 99.90%. The adsorption kinetics conformed to the pseudo-first-order kinetic PFO model, R2 = 0.9937, K1 = 0.07 min–1, qe = 13.30 mg·g–1. The isothermal adsorption process conformed to the Freundlich model, R2 = 0.9950, n >1 at 35 °C. The thermodynamic analysis results show that the adsorption reaction is a spontaneous endothermic physical adsorption process. This study realized the high-value conversion of coal gasification fine slag to high-performance activated material, which not only alleviated the pressure of industrial solid waste disposal but also provided a low-cost technical solution for phenol-containing wastewater treatment, with significant environmental and economic benefits.