Biochar-Reinforced Metal Oxide Photocatalysts for the Removal of Dyes and Pharmaceutical Pollutants: A Review

The increasing discharge of organic pollutants, including dyes and pharmaceuticals, into water bodies poses a severe environmental threat. Industrial activities alone contribute to 17–20% of global water pollution through the release of untreated dye effluents. Recent advancements demonstrate that biochar-reinforced metal oxide photocatalysts (BSPs) enhanced efficiency for pollutant degradation, achieving removal rates up to 99.2% for dyes like methylene blue and 94% for pharmaceuticals such as malachite green under visible-light irradiation. However, challenges remain in scaling up BSP applications due to inconsistent feedstock properties, poor stability, and limited regeneration capacity. This review identifies these critical gaps and provides a comparative analysis of BSP compositions, synthesis methods, and photocatalytic efficiencies. Furthermore, it recommends future studies to focus on optimizing pyrolysis parameters, designing multifunctional composites to improve charge separation, and integrating BSPs into solar-driven reactor systems for sustainable treatment solutions. The review also advocates for comprehensive ecotoxicity and life-cycle assessments prior to field deployment.