UV Light-Irradiated Photocatalytic Degradation of Coffee Processing Wastewater Using TiO2 as a Catalyst

Abstract

The coffee industry generates a significant amount of wastewater that is rich in organic loads and is highly acidic. The present study investigates the potential of the heterogeneous photocatalytic oxidation process to reduce the pollutant load in coffee processing wastewater. The experimental runs were conducted to evaluate the effect of operative parameters such as pH, catalyst dosage, intensity of UV light irradiation, and addition of oxidant on Chemical Oxygen Demand (COD) and colour reduction. Significant results for COD and colour removal, 67%, and 70% respectively, were achieved at a pH of 4 with titanium dioxide (TiO2), and a catalyst dosage of 500 mg/L, using four ultraviolet-C (UV-C) lamps of 16 W each. With the addition of hydrogen peroxide (H2O2) as an oxidant, the removal efficiency increased to 84% and 75% for COD and colour, respectively. Finally, the best results obtained by photocatalytic degradation using UV light were compared to those using solar light. Based on the investigation, it was inferred that the pollutant removal efficiency in coffee pulping wastewater was also considerably high under sunlight. These findings may have relevance in terms of application in countries where coffee processing is carried out and where sunlight irradiance is usually strong: the technique could be exploited to decrease the pollutant content of this wastewater sustainably.