Experimental Mixture Design for Optimization of CeO₂/TiO₂/Biochar Composite Catalyst for Enhanced Brewery Wastewater Treatment Using an Integrated Adsorption–Photocatalytic Process

The brewing industry plays a crucial place in the global economy during manufacturing enormous amounts of wastewater generated containing excessive organic pollutants. The release of untreated brewery wastewater into water bodies causes severe consequences for the environment and human health. The primary objective of this work is to treat brewery wastewater effectively by synthesizing a novel composite material consisting of biochar, cerium oxide and titanium oxide. Biochar was synthesized from malt bagasse by pyrolysis at 360 °C for 1 h using nitrogen gas. Biochar, cerium oxide and titanium oxide were mixed with 10 M nitric acid solution maintained at 140 °C for 4 h, and the resultant mixture was cooled, filtered and dried. The D-optimal experimental design was used to identify the optimum composition of the composite. The impact of component fractions on individual factors was analysed using statistical analysis, and the empirical model was developed. At optimum condition (13.32% by weight of cerium oxide, 13.33% by weight of titanium oxide and 73.33% by weight of biochar) by the process of adsorption and photocatalysis, 66.38 ± 1.88% of chemical oxygen demand and 53.58 ± 1.45% of total dissolved solid were removed after 320 min. The desirability scores for chemical oxygen demand removal (%) and total dissolved solids removal (%) were found to be 0.9654 and 0.9488, respectively, indicating its effectiveness. Further, the kinetic investigation was performed using the Langmuir–Hinshelwood model. Thus, the optimized cerium oxide/titanium oxide/biochar composite is an efficient photocatalyst for brewery wastewater treatment.