Facile synthesis of Fe3O4/ZnO/GO photocatalysts for decolorization of acid blue 113 under solar, visible and UV lights

Abstract

The Fe3O4/ZnO/GO magnetic photocatalyst was successfully produced by low-temperature hydrothermal and used to remove the acid blue 113 (AB113) dye. In this study, three radiation sources were used for the photocatalytic activity, which were the solar source, visible light source and UV source. Through the employment of different analyses methods, i.e., SEM, XRD, TEM, FTIR, BET and BJH analysis, Photoluminescence spectroscopy (PL), UV-vis absorption spectra, VSM, the characteristics of the synthesized catalyst were assessed. According to Tauc's graph, the band gap value from 3.42 eV for ZnO decreased to 1.81 eV for Fe3O4/ZnO/GO composite. Therefore, the synthesized Fe3O4/ZnO/GO catalysts compared to ZnO and Fe3O4/ZnO catalysts showed significant photocatalytic activity in the degradation of AB113 under visible light. Magnetization of catalyst enabled the catalyst to maintain its efficiency after 8 recycling times and only about 15% reduction was observed after 8 recycling runs. The comparison was performed among three radiation sources with a concentration of 100 mg/L of AB113 and the results showed that the use of UV radiation after 50 min produced a 100% removal efficiency and complete removal when using visible radiation in 120 min. But photocatalytic degradation by solar radiation had a removal percentage of 89.2. The reaction rate coefficient for sunlight, UV light, and visible light were 0.075, 0.047, and 0.015 1/min, respectively. Toxicity results using Daphnia Magna showed that the use of visible light and UV light was able to eliminate the toxicity of the dye solution and the use of a solar source was able to provide a 90% reduction in toxicity. Finally, all three processes can be used as pre-treatment before biological processes, which were approved using the BOD5/COD ratio, and all three processes have been able to convert non-biodegradable wastewater into biodegradable wastewater.