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

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.

Automated summary

This study synthesized a series of Ni-ZnS/g-C3N4 nanocomposites, showing high photocatalytic degradation efficiency of RhB, MB, and paracetamol under visible light without toxic by-products. The establishment of an electron transfer mechanism highlights the importance of separating charge carriers for effective pollutant degradation.