Development and characterization of solar active Ag-ZnO/g-C3N4 as a highly efficient photocatalyst for the detoxification of organic pollutant

Abstract

In today's biosphere, a major problem is water pollution caused by the discharge of effluents from dying industries, such as the printing and textile industries. In our current work, we have successfully fabricated photocatalytic bare and composite material 1%Ag-ZnO/6% g-C3N4 (Ag-ZnO/gCN), along with pristine ZnO and g-C3N4 (gCN), for the efficient degradation of dye wastewater. Structural investigations performed using FT–IR, XRD, FE–SEM/EDS, XPS, PL, EIS, and HR-TEM/EDS confirmed the structures of the pristine and composite photocatalysts. According to XPS studies, Ag exists in the metallic form. The photocatalytic performance of all the catalysts was evaluated by degrading methylene blue (MB) dye in an aqueous solution under direct sunlight illumination, and the most active composite catalyst was utilized for conducting dye degradation under visible light in the optimized experimental conditions. The effects of operating parameters, such as catalyst amount and initial pH, on MB degradation have been evaluated. Under solar irradiation, the photodegradation of MB dye over the Ag-ZnO/gCN composite catalyst was measured to be ≈ 100% in 50 min, and its degradation rate constant Kapp (0.1266 min–1) was higher than that of other pristine and composite catalysts. A Total Organic Carbon (TOC) study validated MB mineralization. Further experimental results corroborate the conclusion that superoxide radical anions (O2•–) play a pivotal role in this degradation process, with hydroxyl radicals (•OH) and photogenerated holes (h+) following suit insignificant. Moreover, after undergoing 5 consecutive cycles, the catalysts exhibited a remarkable photostability of 88%. A possible photocatalytic mechanism was proposed for the improved photocatalytic activity.