Biosynthesis of Gold- and Silver-Incorporated Carbon-Based Zinc Oxide Nanocomposites for the Photodegradation of Textile Dyes and Various Pharmaceuticals

Wastewater contaminated with dyes from the textile industry has been at the forefront in the last few decades, thus, it is imperative to find treatment methods that are safe and efficient. In this study, C. benghalensis plant extracts were used to synthesise by mass 20 mg/80 mg zinc oxide–carbon spheres (20/80 ZnO–CSs) nanocomposites, and the incorporation of the nanocomposites with 1% silver (1% Ag–ZnO–CSs) and 1% gold (1% Au–ZnO–CSs) was conducted. The impact of Ag and Au dopants on the morphological, optical, and photocatalytic properties of these nanocomposites in comparison to 20/80 ZnO–CSs was investigated. TEM, XRD, UV-vis, FTIR, TGA, and BET revealed various properties for these nanocomposites. TEM analysis revealed spherical particles with size distributions of 40–80 nm, 50–200 nm, and 50–250 nm for 1% Ag–ZnO–CSs, 1% Au–ZnO–CSs, and 20/80 ZnO–CSs, respectively. XRD data showed peaks corresponding to Ag, Au, ZnO, and CSs in all nanocomposites. TGA analysis reported a highly thermally stable material in ZnO-CS. The photocatalytic testing showed the 1% Au–ZnO–CSs to be the most efficient catalyst with a 98% degradation for MB textile dye. Moreover, 1% Au–ZnO–CSs also exhibited high degradation percentages for various pharmaceuticals. The material could not be reused and the trapping studies demonstrated that both OH• radicals and the e− play a crucial role in the degradation of the MB. The photocatalyst in this study demonstrated effectiveness and high flexibility in degrading diverse contaminants.