Activated Carbon Doped with Silica and Nitrogen as Novel Adsorbent for Enhancing Adsorption Capacity of Cr(VI)

Due to the environmental concerns and the potential hazards and risks posed by chromium (VI), its removal from aquatic habitats has become a serious demand. In this paper, novel modifications were employed to increase the adsorption performance of Cr (VI) using activated carbon (AC) derived from sugarcane bagasse activated with phosphoric acid. AC was consequently modified with triethoxysilane propylamine and diethylene triamine as silica (Si) and nitrogen (N) sources, respectively. SEM-EDX, N2 adsorption isotherms and FTIR analyses were performed to characterize the adsorbents. Equilibrium adsorption behavior of Cr(VI) ions with respect to varying in surface characteristics of resulting materials was investigated using Langmuir, Freundlich and Temkin isotherms. Kinetic and thermodynamic studies of Cr(VI) adsorption over AC, Si@AC and Si-N@AC were carried out. Freundlich model described the adsorption isotherm of AC and Si-N@AC severally, suggesting that the Cr(VI) removal was multi-layer adsorption. However, Langmuir model satisfied with adsorption of Cr (VI) over Si@AC. Pseudo-second order model fitted well the adsorption suggesting the chemical interaction. As a result of doping AC with Si and N, high adsorption capacities obtained at pH 2 and 30oC were to be 268 and 233 mg/g for Si@AC and Si-N@AC which are especially superior compared to others in literature.