Photocatalytic degradation of caffeine in a slurry reactor with intermittent UV irradiation: optimization and response surface modelling

Abstract

This study focusses on the photocatalytic degradation of caffeine (CAF), a stimulating drug and environmental contaminant that poses a threat to humans and the environment. The effect of operating parameters such as CAF initial concentration (5–20 mg/L), catalyst dosage (0.1–0.9 g/L) and pH (3.0–9.0) were explored in detail. The experimental results showed the maximum CAF and chemical oxygen demand (COD) removals of 87.2% and 66.7% respectively. The optimized parameters were: CAF initial concentration – 5 mg/L, catalyst dosage – 0.5 g/L and pH – 7.2. The photocatalytic degradation of CAF followed pseudo-first order kinetics. The obtained experimental data were analysed with response surface methodology (RSM) using Design Expert Software. HIGHLIGHTS The optimized parameters were: [CAF]=5 mg/L, [TiO2]=0.5 g/L, pH=7.2.; The maximum CAF and COD removals were 86.7 and 66.7% respectively.; CAF and COD removals followed pseudo-first-order kinetics.; Good agreement between experimental and predicted data.; All operating parameters were significant in CAF and COD removals.;

Keywords

• caffeine
• cod
• photocatalysis
• tio2