Adsorption behavior of Ni(II) onto activated carbons from hide waste and high-pressure steaming hide waste

This work reports the preparation and adsorption of Ni(II) via activated carbons which produced from hide waste (HWAC) and high-pressure steaming hide waste (HWSAC) with potassium silicate as the activating agent. The best preparation condition for HWAC and HWSAC was the activation temperature of 700 °C using an impregnation ratio of 2:1. Both of them were characterized by N₂ adsorption/desorption isotherms, SEM and FT-IR spectra. The surface area of HWAC and HWSAC was 1804.37 and 1361.26 m²/g, respectively. Despite the surface area of HWAC being larger than that of HWSAC, but the adsorption capacity of Ni(II) for HWAC was lower than that for HWSAC. Furthermore, the adsorption capacity of Ni(II) for both HWAC and HWSAC showed pH-dependent behavior and increased with the increase in pH value, which can be attributed to the functional groups of HWAC and HWSAC materials through the electrostatic attraction. The adsorption data for HWAC and HWSAC were fitted with four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first order model, pseudo-second order model, intra-particle diffusion and Elovich equation), indicating that Langmuir isotherm and Pseudo-second order model fitted well with high coefficient of determination (R² > 0.99) for both the two adsorbents. The positive enthalpy of adsorption (ΔH) and free energy of adsorption (ΔG) indicate a spontaneous and endothermic nature of the process. These results demonstrated that activated carbon can be prepared from hide waste which could remove heavy metal such as Ni(II) effectively.