Designing of experiments for evaluating the interactions of influencing factors on the photocatalytic activity of NiS and SnS2: Focus on coupling, supporting and nanoparticles

Abstract

Synergistic photocatalytic activity of SnS2 and NiS supported was observed by coupling and supporting the semiconductors onto clinoptilolite nanoparticles (NC). Formation of electrical double layer at the semiconductors’ interface in the coupled semiconductors significantly prevented from electron/hole recombination which in turn enhanced the photodegradation activity. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) confirmed enhancement in charge transfer efficiency of the coupled/supported system with respect to the mono-component systems. Consequently the coupled/supported system showed the best photodegradation activity in degradation of metronidazole (MZ). The response surface methodology (RSM) showed that irradiation time, solution pH and interactions of time-CMZ and time-pH are the most important factors in MZ degradation. The best degradation extent was obtained at pH 4, catalyst dosage of 3gL−1, 3mgL−1 of MZ at irradiation time of 270min. R2 of 0.9743 confirmed that the data predicted by RSM well agree with the experimental results. Catalyst dosage and irradiation time had synergistic effect and initial pH and CMZ had an antagonistic effect on the response, meaning that increasing in time and catalyst dosage and decreasing in pH and CMZ decreased MZ photodegradation. Sharp decrease in the UV–Vis absorption at 319nm and increase in the intensity at 240 and 206nm during the process confirmed converting the nitro group and nitrogen existing in MZ to nitrite ion.