Synthesis and characterization of gold nanoparticles (AuNPs) and ZnO decorated zirconia as a potential adsorbent for enhanced arsenic removal from aqueous solution

In this study, gold nanoparticles (AuNPs) and ZnO-decorated zirconia (AuNPs/ZnO-ZrO2) were synthesized through co-precipitation and hydrolysis coupled with heat treatment, and explored as a novel adsorbent for arsenic removal from aqueous solution. The effects of synthesis parameters were examined, such as support type, Zn/Zr mole ratio, co-precipitation method and calcination temperature. X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and N-2 adsorption were used to investigate the enhancement of arsenic adsorption on the hybrid composites. It was found that the adsorption property of AuNPs/ZnO-ZrO2 was strongly dependent on support type, Zn/Zr mole ratio, co-precipitation method and calcination temperature. The optimized AuNPs/ZnO-ZrO2 exhibited the best adsorption capacity for arsenic at lower concentrations (less than 8 mg L-1), compared with ZnO-decorated zirconia (ZnO-ZrO2) and bare zirconia (ZrO2). The enhanced adsorption of arsenic by AuNPs/ZnO-ZrO2 was ascribed to the larger specific surface area, abundant hydroxyl groups and co-existance of ionic gold (Au(OH)(2)(+)) and gold clusters (Au delta+) highly dispersed on the surface which could act as smart scavengers for low-concentration arsenic from water. The adsorption equilibrium of arsenic on AuNPs/ZnO-ZrO2 fitted to the Langmuir, Brunauer-Emmett-Teller (BET) and Gunary models well and the Gunary model gave the best fit. Isotherm analysis results showed that the adsorption of arsenic on AuNPs/ZnO-ZrO2 occurred dominantly through monolayer formation but was a non-ideal Langmuir type adsorption. However, ZnO-ZrO2 showed much higher adsorption capacity for arsenic than that of ZrO2, which was mainly attributed to the formation of basic zinc carbonate (BZC) with rich structural hydroxyl groups and to the improvement in surface properties of zirconia. Significant multilayer adsorption was able to proceed on the surface at higher arsenic concentrations (more than 8 mg L-1), obeying the BET isotherm. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

In this study, gold nanoparticles and ZnO-decorated zirconia composites were synthesized and used as adsorbents for arsenic removal from water. The optimized composite exhibited enhanced adsorption capacity for low concentrations of arsenic.