Effect of pH on photocatalytic degradation of methylene blue in water by facile hydrothermally grown TiO2 nanoparticles under natural sunlight

Abstract

Each year, the production of synthetic dye wastewater reaches a trillion tons. This poses a significant global challenge of water scarcity. Hence, wastewater must be treated to reverse to useable water and prevent water scarcity. Failing to achieve this reversal increases ecotoxicological risks and human health. Textile wastewater contains harmful dyes. Photocatalytic degradation of these dye-contaminated wastewater is one of the major pathways in achieving reversal. However, this process is time-consuming, requires high-power lamps, and is expensive. Here, we report the effect of TiO₂ nanostructures prepared by facile hydrothermal synthesis on the dye degradation of one of the most common industrial textile dyes, methylene blue (MB), under natural sunlight. The impact of particle size on the photocatalytic activity and photocarrier migration rate was thoroughly examined. The size and surface morphology of the TiO₂ nanostructures depended on the concentration of the precursor during synthesis. Also, the effect of the pH of the dye solution on adsorption and photocatalytic degradation has been evaluated. With several optimized conditions, almost complete dye degradation was achieved within 40 min under the direct illumination of natural sunlight. The enhanced photocatalytic performance could correlate to the synergetic effect of a higher charge transfer mechanism, good catalytically active surface area availability (386 m²/g), and several optimized parameters that affect the reaction efficacy. Additionally, repeated use of NPs (five times) without sacrificing performance confirmed their stability and sustainability as a promising candidate for large-scale industrial textile wastewater remedies.