Green and environmentally sustainable fabrication of SnS2 quantum dots/chitosan nanocomposite for enhanced photocatalytic performance: Effect of process variables, and water matrices

Abstract

Concerns over the availability of clean water and the quality of treated wastewater are significant problems that call for an appropriate solution to improve the water quality. The present work emphasized the synthesis of novel SnS₂ quantum dots (QDs) deposited on chitosan via a facile green precipitation method involving neem (Azadirachta indica) leaf extract and investigating its photocatalytic performance for the degradation of Crystal violet (CV) dye under varying reaction parameters, other organic and inorganic salts and water matrices. The crystal structure, surface morphology, and elemental composition of the prepared SnS₂ (QDs)/Ch composite were evaluated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and energy dispersive X-ray analysis (EDAX) techniques. The average size of SnS₂/Chitosan nanoparticles was calculated to be 8.8 nm using XRD, with the average diameter of SnS₂ QDs to be 3.3 nm from TEM. UV-visible spectroscopy was used to investigate its optical properties. The direct band gap of SnS₂/Chitosan estimated from Tauc's plot came to be 2.5 eV. The prepared novel SnS₂/Ch composite showed outstanding photocatalytic activity for the degradation of CV through the Advanced Oxidation Process (AOP). The fabricated photocatalyst caused 98.60 ± 1.34 % degradation of CV within a short period of 70 min under optimum conditions. The photodegradation reaction followed pseudo-first-order rate kinetics with a rate constant of 0.0815 min^-1. Furthermore, the photocatalyst showed high stability and was reusable for up to four cycles. The present work fulfils the aim of designing a novel, green, and efficient visible light-active nano-photocatalyst.

Keywords: AOP; Chitosan; Crystal violet; Green synthesis; Photodegradation; SnS(2) quantum dots.