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This study is focused on preparation of pristine zinc sulphide (ZnS) and zinc sulphide/kaolinite (ZnS/K) nanocomposite using one-pot hydrothermal synthesis under atmospheric pressure and without any surfactant. Together with finding a simple preparation method, the aim was to achieve a high photocatalytic activity, and also reduce the environmental risk of ZnS (in the case of ZnS/K). Pristine ZnS was synthesized from aqueous solutions of zinc chloride and sodium sulphide in various ratios. ZnS/K nanocomposite was prepared similarly by addition of kaolin KKAF into the mixture of zinc chloride and sodium sulfide solutions. Reaction mixtures were continuously stirred at 100°C for several hours, resulting white solids were separated by centrifugation, washed with distilled water, and dried at 105°C overnight. X-ray powder diffraction analysis revealed the presence of cubic modification sphalerite both in ZnS and ZnS/K samples. Amount of ZnS in ZnS/K (~32 wt.%) was determined by Rietveld method which also confirmed the sphalerite structure. Morphology of the samples was observed using scanning electron microscopy. In the case of ZnS/K, the ZnS nanoparticles anchored on the kaolinite surface were observed. Photocatalytic activity evaluated using discoloration of Acid Orange 7 (AO7) in a liquid phase was found very high for ZnS samples. After 1 h of UV irradiation, ~99% of AO7 was degraded by ZnS. Photodegradation efficiency reached 96% in the case of ZnS/K. Taking into account that only ~32 wt.% of ZnS is present in ZnS/K, the photocatalytic activity of the nanocomposite can be considered three times higher compared to pristine ZnS.
Keywords: ZnS, kaolinite, hydrothermal synthesis, photoactivity, nanocomposite© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.