An effective wastewater treatment based on sunlight photodegradation by SnS2-ZnS/clinoptilolite composite

The SnS2-ZnS/clinoptilolite nanoparticles (SnS2-ZnS/NC) was used for the effective photodegradation of an oil refinery wastewater sample contained phenol as the major component. Band gap energy of SnS2/NC (3.28 eV) showed a considerable red shift with respect to ZnS-SnS2/NC (2.9 eV). Mole ratio of the semiconductors in the coupled system played an important role in the activity of the resulted composite, so the SnS2-ZnS-NC system containing 0.65 mol ZnS and 0.35 mol SnS2 (ZnS/SnS2: 1.85) showed the best photocatalytic activity. This confirms the best charge carriers' separation occurred between the semiconductors in the composite. The RSM results showed acidic pHs at longer irradiation times, higher catalyst dosage and lower concentration of the pollutant caused to increase in the degradation extent. The best run included pH 4, catalyst dose of 2.3 g L-1, 10 folds diluted wastewater at irradiation time of 60 min. The photodegradation pathway was a direct Z-scheme mechanism and the following trend was obtained in the role of the reactive species in phenol degradation: Holes > (OH)-O-center dot > electrons>O-center dot(2)-.