Degradation of methyldiethanolamine and gas refinery effluent using a TiO2@WO3/ZnO photocatalyst: central composite design optimization

Abstract

A TiO₂@WO₃/ZnO photocatalyst was synthesized and employed in the degradation of methyldiethanolamine (MDEA) (a pollutant of wastewater from gas refinery complexes) under LED light. The synthesized photocatalyst was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectrometry (FT-IR). In the wastewater treatment process, a number of experiments were designed by central composite design, where parameters including the irradiation time, pH, TiO₂@WO₃/ZnO catalyst mass and MDEA concentration involved in the process were optimized. The significance of the individual parameters and their possible interactions were investigated using analysis of variance. The optimum values of 30 min, 9, 0.15 g, and 0.4% were obtained for the irradiation time, pH, TiO₂@WO₃/ZnO catalyst mass ratio and the initial concentration of MDEA, respectively. Under such conditions, the photodegradation percentage of MDEA was 86%, and a maximum photocatalytic activity with 72% degradation of gas refinery effluent was achieved in 70 min.