Green Synthesized SiO2 Nanoparticles from Hibiscus rosa sinensis Extract for Photocatalytic Pollutant Degradation from Textile Wastewater and Ecotoxicological Assessment

The surge in population and industrialization further exacerbated by climate change have emerged into an unprecedented global water crisis. Over half of global population lacks access to safe drinking water and the situation is projected to worsen in near future. This has necessitated the development of advanced wastewater treatment systems capable of producing high-quality effluent. In present scenario an economical, and ecologically safe material for environmental remediation is warranted. The present study addresses the synthesis of SiO₂ NPs from Hibiscus rosa sinensis flower extract for wastewater treatment. The presence of siloxane and Si–O bonds was affirmed from FTIR spectroscopy. A band gap of 3.02 eV was estimated for the NPs from the Tauc plot. The NPs constituted an average particle size of 19.9 nm with a zeta potential of –49 mV. Photocatalytic efficacy of SiO₂ NPs was investigated for individual dyes namely methyl orange, eosin yellow and methylene blue and their ternary mixture under sunlight. The NPs were remarkable photocatalyst for degradation of textile dyes and exhibited good stability till the fourth cycle of reuse. Furthermore, the SiO₂ NPs-loaded cotton fabric exhibited excellent photocatalytic performance in terms of removal of 90% of dye, thereby validating its efficacy towards development of self-cleaning fabrics. The efficacy of the green NPs as a nanofertilizer was examined for okra seeds and NPs concentration upto 100 mg/ L stimulated the shoot elongation without any adverse impact. The ecotoxicological impact of photodegraded dye solution on growth of okra seeds indicated no inhibitory phytotoxic effect. Thus, the green synthesized SiO₂ NPs using red hibiscus flower extract are sustainable photocatalysts for degradation of anthropogenic organic pollutants and design of smart textiles. Furthermore, the ecological safety assessment asserted the potential use of photodegraded water for sustainable agriculture.

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