Removal of Ni²⁺from aqueous solution by blast furnace sludge as an adsorbent

The blast furnace sludge (BFS), by-product and waste material of steelmaking industry was utilized as an adsorbent for Ni2+ ions removal from aqueous solution. Chemical and mineralogical composition of BFS was examined by Proton Induced X-ray Emission (PIXE) and X-ray Diffraction (XRD) methods. The structural properties of BFS were characterized using Brunauer-Emmett-Teller (BET) and Scanning Electron Microscopy (SEM) methods. Batch experiments were conducted to evaluate the adsorption performance. The equilibrium adsorption level was determined to be a function of the solution concentration and temperature. Two simple kinetic models, pseudo-first and second-order, were used to investigate the adsorption mechanisms. The pseudo-second-order reaction kinetics provides the best correlation with the experimental data. The equilibrium data were analyzed using the Langmuir and Freundlich isotherms. The characteristic parameters for each isotherm were found. The results obtained from Freundlich's isotherm are slightly better than those obtained from Langmuir's isotherm. The thermodynamic parameters have been determined. The negative values of free energy change (ΔG) indicated the spontaneous nature of the adsorption of Ni<sup>2+</sup> on blast furnace sludge and the positive values of enthalpy change (ΔH) suggested the endothermic nature of the adsorption process. The observed adsorption capacity for Ni<sup>2+</sup> ions is a good indicator of BFS potential for its use in aqueous sorption system