Structural reconfiguration of Al/CaO adsorbent by Ni doping to improve sintering resistance and arsenic removal performance

Abstract

CaO-based adsorbents have poor adsorption performance due to high temperature sintering. In this study, a trace amount of Ni was added to an Al/CaO adsorbent using the Pechini hydrothermal method and anhydrous grinding method. The modified adsorbent was then used to remove As2O3, and both experimental and theoretical approaches were employed. The experimental results showed that the addition of Ni transformed the surface of the adsorbent from a two-dimensional network structure to a three-dimensional cluster structure, significantly increasing its specific surface area and improving its adsorption capacity for As2O3. The adsorption capacity reached 933.1 mg/kg at 900 °C, which was 3.79 times higher than that of pure CaO and 8.2 times higher than that of Al2O3. Additionally, the presence of nano-scale NiO particles prevented the sintering of CaO grains, allowing the adsorbent to maintain its pore structure even after the reaction. Density functional theory (DFT) calculations showed that NiO was the most active site for As2O3 adsorption on the surface of Al/Ni-CaO. Ni acted as an electron transport bridge, enhancing electron transfer on the material's surface and increasing adsorption energy. These findings are important for future research on high-temperature removal of As2O3 with doped CaO-based adsorbents.