Cu doped TiO2-Bi2O3 nanocomposite for degradation of azo dye in aqueous solution: Process modeling and optimization using central composite design

Abstract

Cu doped TiO2-Bi2O3 hybrid as a visible active photocatalyst was syhthesized by a sol-gel method and the weight fraction of Cu (1–5 wt. %), and Bi2O3 (3–8 wt. %) was optimized using response surface methodology. The photodegradation of methyl orange (MO) was carried out to evaluate photoactivity properties of the prepared samples under visible light irradiation. The Cu-TiO2-Bi2O3 nanocomposite with a weight fraction of 1 and 8% for Cu and Bi2O3 has the best photocatalytic activity for MO degradation. The characteristics of photocatalyst with optimum composite (1 wt. % of Cu and 8 wt. % Bi2O3) were also investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and diffuse reflectance spectra (DRS). The DRS spectra approved that the adsorption wavelength of Cu doped TiO2-Bi2O3 is in the visible light range (470 nm).The influence of amount of catalyst (0.8–1.2 g L−1), MO concentration (10–20 mg L−1)and initial pH of the solution(4–6) in on MO photodegradation was modeled and optimized using central composite designe based on response surface methodology.The value of MO removal decreases by about 15% when MO concentration increases from 10 to 20 mg L−1. Maximum dye removal was achieved about 74% at 10 mg L−1 of MO, 1.2 g L−1 catalyst loading and pH of 4.