A Novel Ag/ZnO/g-C ₃ N ₄ (A/ZCN) Nanocomposite for Photocatalytic Treatment of Organic Dyes in Aqueous Solution

This study aims to prepare a ternary nanocomposite Ag/ZnO/g-C3N4 (A/ZCN) by physical mixing and calcination in one step to enhance the decomposition of methylene blue (MB) in an aqueous solution. The as-prepared A/ZCN composite has a well-organized structure. The composite is arranged in clusters of 3–4 particles with a size of about 20.2 nm similar to soap bubbles. The A/ZCN sample exhibits better visible light absorption performance than ZnO. The A/ZCN nanocomposite effectively utilizes the advantages of ZnO and g-CN as well as the Surface plasmon resonance effect of Ag to degrade MB. The mechanism of photocatalytic degradation of MB on the composite by radicals was proposed and the effects of reaction factors on MB degradation were comprehensively studied. Under the optimal conditions (A/ZCN of 0.5 g/L, MB of 10 mg/L, pH of 6.5, and temperature reaction 30°C), the reaction proceeds rapidly with a rate constant (kap) of 0.027 min−1 and the A/ZCN composite can degrade 94.0% of MB after 90 min of illumination under visible light while the direct degradation is almost invisible and in the absence of a catalyst is only below 5%. Under UV irradiation, the MB decomposition efficiency reached 95.7% with a kap of 0.033 min−1. The reusability of the catalyst remained at approximately 66.4% after four cycles. The performance of the A/ZCN nanocomposite was also evaluated by the degradation of recalcitrant organic compounds, including antibiotics, volatile organic compounds, and organic dyes. In addition, it also exhibited superior performance compared with other catalysts reported in the literature. Overall, the A/ZCN nanocomposites synthesized by a simple calcination method demonstrated significant potential for the degradation of organic pollutants in wastewater treatment applications.