Degradation of persistent organic pollutant using Ag-doped ZnO-ZnS–polyaniline composite as photocatalyst

Textile industries release dye-laden polluted wastewater into the environment. The dye causes long-term impact as it is harmful to living organisms and block the penetration of sunlight in the water body. Advanced oxidation processes like photocatalysis are recently gain popularity as one of the promising techniques among various wastewater treatment methods. In this study, the Ag-doped ZnO-ZnS/polyaniline (Ag/ZnO-ZnS/PANI) photocatalyst was synthesized by using a simple coprecipitation method followed by ultrasonic-assisted deposition of Ag and then in-situ oxidative polymerization. The sample was characterized by different techniques like FTIR, XRD, SEM, EDS, and XPS. The photocatalytic activity of the composite was tested for degradation of dye methylene blue under the UV light. Under optimum conditions of pH = 6 photocatalyst dose = 0.005 g/100 mL, dye concentration = 10 mg/L, oxidant dose = 3 mM, and reaction time = 90 min, it was found that Ag-doped ZnO-ZnS/PANI showed better activity as compared to undoped composites. The photocatalytic degradation was increased from 62, 72, 86 to 95% for ZnO-ZnS, Ag/ZnO-ZnS, ZnO-ZnS/PANI, and Ag/ZnO-ZnS/PANI composites, respectively. The photocatalysis of dye onto Ag/ZnO-ZnS/PANI followed Langmuir–Hinshelwood kinetic model. The radical scavenging test was conducted to observe the role of the main reactive species. The present work presented an effective approach for the photocatalytic treatment of polluted water by using a promising material.