Photocatalytic Degradation of Acidic and Basic Dye by ZnS and Tin-Doped ZnS Nanocatalysts

Zinc sulphide (ZnS) nanomaterials were hydrothermally prepared and doped with 2% Tin (Sn). UV–Visible, X-ray Diffraction (XRD), Energy-Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM), Fourier transform Infrared (FTIR) spectroscopy and Thermogravimetric analysis (TGA) were used to characterize the produced NPs. With successful doping, the band gap of ZnS nanomaterials decreased from 3.50 to 3.10 eV. Cubic crystal structure of ZnS and Sn-ZnS nanomaterials was shown by XRD with the average particle size of 16.30 and 18.62 nm, respectively. ZnS nanomaterials were found to have spherical shape, and no change in shape was noticed with Sn-doping. Using TGA analysis, 22.8% and 21.5% weight loss was observed in Zinc sulphide and Tin-doped ZnS nanocatalyst, respectively, at heating range of 40–600 °C revealing their stability to temperature. The synthesized nanoparticles were also used for the photodegradation of Coomassie Brilliant Blue G-250 (CBB G-250) and Basic Blue-3 (BB-3) dyes in aqueous solution. For photodegradation reaction using bare ZnS and Sn-doped ZnS nanomaterials, activation energies of 8.6 kJ/mol and 32.1 kJ/mol were calculated for ZnS and Sn-ZnS NPs, respectively. First-order reaction kinetics was followed by the photodegradation of both the dyes using these NPs. About 84% and 93% degradation was observed for CBB G-250 dye using bare and Sn-doped ZnS NPs at 240 min time interval while using the same nanoparticles for the degradation of BB-3 dye the degradation reached 83% and 95% at 360 min time, respectively. Low concentration (10 ppm) of dyes, maximum dosage (0.03 g) of the catalysts and increasing temperature up to 70 °C favoured the photocatalytic degradation. Per cent degradation of both the dyes was found higher at low pH(3.5). Both bare Zinc sulphide and Sn-doped Zinc sulphide nanomaterials could be recycled for the given dyes detoxification as shown by the recyclability of the used catalysts, but the performance of Sn-ZnS was higher as compared to pure ZnS. Results of antibacterial studies revealed that the synthesized NPs were more active against E. coli in all concentration as compared to others.