Excellent visible-light-driven Ni-ZnS/g-C3N4 photocatalyst for enhanced pollutants degradation performance: Insight into the photocatalytic mechanism and adsorption isotherm

Abstract In this paper, a series of nanocomposites consisting of different weight percentages of nickel-doped ZnS (Ni-ZnS)/graphitic-C3N4 (g-C3N4) have been synthesized via solid-state calcination of a mixture of pure g-C3N4 and 10 mol% Ni-ZnS. The proposed solid-state method is simple and provides a general route to make composite photocatalysts on a large scale. The shift in XRD peaks to lower theta value validates Ni+2 ion could be introduced effectually into the lattice of ZnS and substitutes to Zn+2 site. The interaction between Ni-ZnS and g-C3N4 in composite materials leads to long-lived charge carriers and efficient visible-light harvesting property. Which in turn showed remarkable high activity for degradation of RhB (92%, in 75 min), MB (96%, in 40 min) and paracetamol (86%, in 100 min), respectively. The photo mineralization of RhB, MB and paracetamol, over the most active 10 wt% Ni-ZnS/g-C3N4 nanocomposite was also evaluated by monitoring the reduction in TOC (total organic carbon) contents with respect to time under the visible light source. High-performance liquid chromatography results showed that no toxic by-products were formed during the photodegradation of paracetamol. On the basis of obtained results, a conceivable electron transfer mechanism has been stretched out for separating charge carriers and emphasizes the importance of superoxide and hydroxyl radicals for the degradation of pollutants in wastewater.