Title: Equilibrium studies, kinetics and thermodynamics of anion removal by adsorption

Authors: Odivan Zanella; Élen Klein; Nathalia K. Haro; Manuela G. Cardoso; Isabel C. Tessaro; Liliana A. Féris

Addresses: Laboratory of Separation and Unit Operations, Department of Chemical Engineering, Federal University of Rio Grande do Sul (UFRGS), Engineer Luis Englert Street, Central Campus, Postcode: 90040-040, Porto Alegre, RS, Brazil ' Laboratory of Separation and Unit Operations, Department of Chemical Engineering, Federal University of Rio Grande do Sul (UFRGS), Engineer Luis Englert Street, Central Campus, Postcode: 90040-040, Porto Alegre, RS, Brazil ' Laboratory of Separation and Unit Operations, Department of Chemical Engineering, Federal University of Rio Grande do Sul (UFRGS), Engineer Luis Englert Street, Central Campus, Postcode: 90040-040, Porto Alegre, RS, Brazil ' Laboratory of Separation and Unit Operations, Department of Chemical Engineering, Federal University of Rio Grande do Sul (UFRGS), Engineer Luis Englert Street, Central Campus, Postcode: 90040-040, Porto Alegre, RS, Brazil ' Laboratory of Membrane Separation Processes, Department of Chemical Engineering, Federal University of Rio Grande do Sul (UFRGS), Engineer Luis Englert Street, Central Campus, Postcode: 90040-040, Porto Alegre, RS, Brazil ' Laboratory of Separation and Unit Operations, Department of Chemical Engineering, Federal University of Rio Grande do Sul (UFRGS), Engineer Luis Englert Street, Central Campus, Postcode: 90040-040, Porto Alegre, RS, Brazil

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.

Keywords: wastewater treatment; kinetics modelling; mechanism; adsorption capacity; activated carbon; isotherms; equilibrium studies; thermodynamics; anion removal; nitrate removal; sulphate removal; aqueous solutions; calcium chloride; pH; Gibbs free energy; enthalpy; entropy; particle diffusion.

DOI: 10.1504/WRSTSD.2016.078412

World Review of Science, Technology and Sustainable Development, 2016 Vol.12 No.3, pp.193 - 218

Accepted: 15 Oct 2015
Published online: 16 Aug 2016 *

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