Kinetics and Optimization Studies of Photocatalytic Degradation of Methylene Blue over Cr-Doped TiO2 using Response Surface Methodology

Abstract

Wastewater containing dyes are difficult to treat attributed to their recalcitrant properties and resistance to biodegradation in conventional activated sludge treatment. Removal of dye via photocatalytic approach appears to be promising. This study was performed to examine the effect of various operating parameters on photocatalytic degradation of methylene blue (MB) over chromium oxide-doped TiO2 followed by optimization study using response surface methodology (RSM) based on Box–Behnken design (BBD). The experiments were carried out at room temperature under visible light irradiation. The dye photocatalytic degradation followed first-order kinetics with rate constant of 0.0301 h−1. The effects of dopant concentration, sample loading and irradiation time were investigated and their binary interactions were modeled. The high regression R2 value of 0.9904 confirmed that the proposed equation fits the experimental data accurately. ANOVA analysis results demonstrated that irradiation time was the most significant individual parameter. Verification test enunciated RSM based on BBD which was suitable to optimize photodegradation of methylene blue over chromium oxide-doped TiO2 photocatalyst.