Eco-inspired magnetic nano-photocatalysts from soapnut for dye degradation

Soapnut (Sapindus sp.), a naturally abundant biomaterial from deciduous trees, offers strong potential for green nanotechnology. In this study, soapnut seed biomass was used to synthesize reduced graphene oxide (rGO)-based magnetic nano-photocatalysts by way of a co-precipitation method followed by hydrothermal processing. X-ray diffraction confirmed the incorporation of silicate composites, enhancing photocatalytic performance. The material exhibited a Brunauer–Emmett–Teller surface area of 65 m2/g, indicating high reactivity. Vibrating sample magnetometer analysis revealed soft magnetic behavior, enabling facile recovery and reuse. Raman spectroscopy confirmed multilayer graphene oxide formation, while field emission scanning electron microscopy showed nanoporous sheet-like and floral structures with sizes ranging from 35 to 65 nm. Ultraviolet–visible diffuse reflectance spectroscopy analysis indicated a bandgap of 1.64 eV, supporting visible-light-driven photocatalysis. The synthesized photocatalyst achieved 82% degradation of malachite green dye within 90 min. This study demonstrates a sustainable, circular approach by converting agricultural waste into multifunctional magnetic nano-photocatalysts for efficient textile dye removal. The work contributes to advancements in material science and wastewater treatment, aligning with UN SDG 6 (Target 6.3) for improved water quality through pollution reduction.