Synthesized Cr/TiO immobilized on pumice powder for photochemical degradation of acid orange-7 dye under UV/visible light: influential operating factors, optimization, and modeling.

The current study aimed to investigate the removal efficiency of acid orange-7 (AO7) using synthesized Cr/TiO immobilized on pumice powder under visible light and UV irradiation. The characterization of synthesized nanocatalyst examined by scanning electron microscope, X-ray diffraction, and Fourier transforms infrared. The optimum of experimental parameters including catalyst dosage, dye concentration, time and pH, D-optimal Design (DOD) along with response surface methodology obtained by R software. The initial and outlet concentration was measured using a spectrophotometer. Besides, Analysis of variance results for the quadratic model showed simple linear regression with high significance and provided as a predicting model. The differences less than 0.2 between multiple and adjusted R in two models indicate that two examined models fitted suitably. The highest removal efficiency of AO7 was 95 and 74% under visible and UV irradiation, respectively. Therefore, the higher removal efficiency in visible light reduces the costs and energy, moreover, offers an environmentally friendly method. The results showed that the removal efficiency of AO7 increased considerably with rising catalyst dosage and time, as well as minimizing dye concentration, and pH.