Synthesis of Tin Oxide Nanoparticles from E-Waste for Photocatalytic Mixed-Dye Degradation under Sunlight

Electronic waste (e-waste) has become a significant environmental concern worldwide due to the rapid advancement of technology and short product lifecycles. Waste-printed electronic boards (WPCBs) contain valuable metals and semiconductors; among them, tin can be recycled and repurposed for sustainable material production. This study presents a potential ecofriendly methodology for the recovery of tin from WPCBs in the form of tin oxide nanostructured powders. The soldering points in the WPCBs are extracted and dissolved in the dilute HNO₃ solution, followed by the formation of metastannic acid, which is subsequently transformed into SnO₂ nanoparticles. Different characterization techniques (XRD, XPS, FE-SEM, and TEM) are employed to confirm the morphology and composition of nanoparticles. The prepared SnO₂ NPs, having a size range of <50 nm, show excellent photocatalytic degradation of cationic (methylene blue, MB) and anionic (eosin Y, EY) dyes for wastewater treatment. The as-synthesized SnO₂ can degrade the mixed dyes (MB+EY) under the illumination of natural sunlight at rate constants of 0.0153 and 0.1103 min^-1 for MB and EY, respectively. The positive zeta potential and smaller particle size of the SnO₂ NPs possess the extra advantage of the adsorption of anionic over cationic dye, resulting in faster degradation of EY, which is further supported by DFT calculation. The synthesis of SnO₂ from waste-printed electronic boards offers a dual benefit: It not only provides a sustainable solution for managing electronic waste but also contributes to the production of useful photocatalysts for wastewater treatment. By converting waste into valuable resources, this approach aligns with the principles of the circular economy and mitigates the environmental impact associated with e-waste disposal.