Strategic separation of metal sulfides from residual wet-chemical precursors for synchronous production of pure water and nanostructured photocatalysts

Abstract

Pseudo successive ionic layer adsorption and reaction (p-SILAR) is an emerging technique for deposition of quantum dots (QDs) on a variety of nanoparticles (NPs); however, it has a limitation of wastage of water-based ionic precursors those are hazardous in nature as well. In this study, we have strategically ensured the removal of ionic species from aqueous solutions, by salvaging efficient metal sulfides (i.e. PbS, CdS, ZnS, CuS, Ag2S, and SnS) exhibiting 62%, 47%, 66%, 86%, 91%, and 99% degradation of Congo-red dye, respectively, resulting a reaction rate of 0.016, 0.011, 0.021, 0.034, 0,083, and 0.04 min−1. The qualitative characterization of successfully salvaged metal sulfide photocatalysts was carried out using scanning and transmission electron microscopy (SEM/TEM), coupled with optical, crystallographic, and elemental elucidation. Importantly, residual aqueous ionic solutions were detoxified and water was brought back to its pure and drinkable state, avowing the standardization of wastewater treatment bi-effectually. Specifically, anionic precursors having pH value of ~ 12 and cationic precursors of SnCl2 and Pb(NO3)2 having pH values of ~ 4 were taken to 7.