Optimization of photocatalytic degradation of Eriochrome Black T from aqueous solution using TiO2-biochar composite

•TiO2-biochar composite synthesized via sol-gel method for photocatalytic degradation.•Optimal Eriochrome Black T removal of 99.14 % achieved under UV irradiation.•Key parameters: pH 3, catalyst dose 1.48 g/L, dye concentration 32 mg/L.•Surface area increased from 38 m²/g to 78 m²/g, enhancing photocatalytic efficiency.•TBC-1 composite shows promise for sustainable wastewater treatment solutions. The untreated release of dye-contaminated effluents into water bodies presents serious threats to both environmental and public health. Efficient dye removal methods are critical for preventing pollution and safeguarding ecosystems. This study aims to optimize the photocatalytic degradation of Eriochrome Black T dye in aqueous solutions using a novel composite of TiO2 and biochar (BC) as a photocatalyst under UV irradiation. The TiO2-BC composite (TBC-1) was synthesized via the sol-gel method and characterized using X-ray diffraction, BET surface area analysis, Fourier-transform infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy. The synthesis resulted in an anatase phase crystal structure, a reduced band gap of 2.69 eV, and a significant surface area increase from 38 m²/g to 78 m²/g. The photocatalytic performance was optimized under UV light using Response Surface Methodology (RSM) with a Central Composite Design (CCD). Key variables, including initial pH (3–11), dye concentration (10–50 mg/L), photocatalyst dosage (0.5–2.5 g/L), and irradiation time (30–150 min), were assessed. An optimal decolorization efficiency of 99.14 % and a mineralization efficiency of 93.7 % were achieved at pH 3, 32 mg/L dye concentration, 1.48 g/L catalyst dosage, and 124 min irradiation time. These findings highlight the potential of the TBC-1 composite as an effective and sustainable solution for water and wastewater treatment applications, contributing to improved environmental management practices.