Green synthesis of SnO₂–TiO₂ nanocomposite using pomegranate peel extract for efficient photocatalytic degradation of Alizarin Red dye

In this work, a SnO₂–TiO₂/PP nanocomposite was successfully prepared by a green chemical precipitation method using pomegranate peel (PP) extract as a natural biogenic additive. The phytochemical compounds present in the extract helped to control nucleation, reduce particle agglomeration, and introduce useful surface functionalities during the formation of the composite. Structural studies confirmed the presence of crystalline anatase TiO₂ and tetragonal SnO₂ phases. TEM analysis showed quasi-spherical nanoparticles with an average particle size of 12.6 ± 3.1 nm. BET results revealed a mesoporous structure with a specific surface area of 22 m² g⁻¹. UV–DRS analysis indicated a reduced band gap of 2.8 eV for the composite. The photocatalytic activity of the SnO₂–TiO₂ nanocomposite was tested for the degradation of Alizarin Red dye under UV light irradiation, where a maximum degradation efficiency of 97.56% was achieved within 100 min. The degradation process followed pseudo-first-order kinetics with an apparent rate constant of 0.01745 min⁻¹. TOC analysis confirmed significant mineralization of the dye solution, and recyclability tests demonstrated good catalytic stability over five successive cycles. The improved photocatalytic performance was mainly attributed to efficient charge separation across the SnO₂–TiO₂ heterojunction, reduced electron–hole recombination, and enhanced dye adsorption due to PP-derived surface groups. Overall, this study demonstrates a simple, sustainable, and effective route for developing photocatalysts for wastewater treatment.