Abstract
In this work, granular activated carbon (GAC) functionalised with CaCl2 was used to remove nitrate and sulphate from aqueous solutions. Functionalisation with CaCl2 influenced the physico-chemical properties and improved the adsorption capacity of activated carbon. The effect of pH on adsorption was investigated, and no significant difference was observed. The adsorption process was found to be of an exothermic nature. Thermodynamic parameters were calculated including the change in Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°). The pseudo-first-order model, pseudo-second-order model and Elovich equation were used to study the adsorption kinetics. The intraparticle diffusion model, Boyd's model and Bangham's equation were investigated to determine the mechanism of this process. The data showed that nitrate adsorption on activated carbon follows second-order kinetics, whereas that of sulphate follows first-order kinetics. The control mechanism for the two components was determined to be particle diffusion.
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