Facile green synthesis of ZnO-CdWO4 nanoparticles and their potential as adsorbents to remove organic dye.

In this work, ZnO-CdWO4 nanoparticles have been synthesized by the ecofriendly green method with lemon leaf extract to favorably anchor functional groups on their surface. The prepared ZnO-CdWO4 nanoparticles are used as adsorbent to treat Congo red (CR) dye after characterization through FT-IR, UV-Vis, TEM, SEM-EDX, and HRTEM techniques. The equilibrium partition coefficient and adsorption capacity values for CR by ZnO-CdWO4 are estimated as 21.4 mg g-1 μM-1 and 5 mg g-1, respectively (at an initial dye concentration of 10 mg L-1). The adsorption process is found as exothermic and spontaneous, as determined by the ΔG°, ΔS°, and ΔH° values. The Boyd plot has been used as a confirmatory tool to fit the adsorption kinetics data along with intraparticle diffusion and pseudo-second-order models. Based on this research, ZnO-CdWO4 nanoparticles are validated as an effective adsorbent for CR dye in aqueous solutions.