Dark catalytic degradation of industrial dye effluents using orthorhombic Tin monosulphide nanocatalyst

Abstract

In this work, we report on the pH-independent, reducing agent-free, fast, dark catalytic degradation of azo dyes using tin mono sulphide nanocatalyst. SnS nanocatalyst with high Sn content has degradation efficiency of ~99%, which is achieved within 60 min of the catalytic reaction. Almost 61% of the dye is degraded within the first 20 min of the commencement of the catalysis. SnS nanocatalyst are shown to degrade the industrial dyes methyl blue (MB), eriochrome black T and congo red with equal efficiency. Orthorhombic SnS nanocatalyst with band gap of 2.29 eV were synthesized by simple homogenous precipitation method at room temperature and characterized using X-ray diffraction, high-resolution scanning electron microscope, energy dispersive X-ray analysis (EDAX), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and UV–Vis absorption spectroscopy. The reaction time (60 min), molarity of precursor (0.6 M of SnCl2) and mass of SnS (40 mg) is optimized to obtain the highest efficiency. The degradation efficiency of SnS nanocatalyst is independent of pH of the dye. It is unaffected by the ambient conditions and works efficiently in both dark and light conditions. The SnS triggered catalytic degradation reaction follows the pseudo first-order kinetics and does not require any additional reducing agents to promote the catalytic activity. The high efficiency of catalytic degradation in SnS nanocatalyst in the absence of reducing agent is attributed to the high number of active sites in SnS due to high Sn concentration. The dye degradation occurs by decomposition of the phthalic acid, bis (2-pentyl) ester toxic compounds to their intermediate compound eicoscene. SnS nanocatalyst assisted dark catalysis can be used to replace the existing photocatalytic and UV assisted advanced oxidation techniques and completely deter the use of reducing agents in catalytic water treatment.