Efficiency of Ag3PO4/TiO2 as a heterogeneous catalyst under solar and visible light for humic acid removal from aqueous solution

Abstract

Nowadays, the presence of humic acid (HA) in water sources is highly regarded due to the production of extremely harmful byproducts such as trihalomethanes. In this study, the effectiveness of an Ag3PO4/TiO2 catalyst produced by in situ precipitation as a heterogeneous catalyst for the degradation of humic acid in the existence of visible and solar light was evaluated. The Ag3PO4/TiO2 catalyst's structure was characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), after which the catalyst dosage, HA concentration, and pH parameters were adjusted. After a 20-min reaction, the highest HA degradation of 88.2% and 85.9% in presence of solar light and visible light were attained at the ideal operating conditions of 0.2 g/L catalyst, 5 mg/L HA, and pH 3, respectively. It was discovered that, based on kinetic models, the degradation of HA matched both Langmuir-Hinshelwood and pseudo-first-order kinetics at concentrations of 5 to 30 mg/L (R2 > 0.8). The Langmuir-Hinshelwood model had surface reaction rate constants (Kc) of 0.729 mg/L.min and adsorption equilibrium constants (KL-H) of 0.036 L/mg. Eventually, a real-water investigation into the process' effectiveness revealed that, under ideal circumstances, the catalyst had a reasonable HA removal efficiency of 56%.