Abstract

GRANADOS-CORREA, F.; BONIFACIO MARTINEZ, J.  and  SERRANO GOMEZ, J.. Kinetic and thermodynamic study of Cr(VI) adsorption on synthetic calcium phosphate in aqueous media. Rev. Soc. Quím. Perú [online]. 2009, vol.75, n.2, pp.201-212. ISSN 1810-634X.

Calcium phosphate was synthesized and characterized to investigate the remove of Cr(VI) anions from aqueous solutions as a function of contact time, pH of the Cr(VI) solution, amount of adsorbent, Cr(VI) concentration and temperature by means of batch experiments. The experimental data were analyzed through Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. Thermodynamic parameters of the adsorption system were determined at various temperatures (293 to 323 K). Results showed that adsorption equilibrium of Cr(VI) ions was attained in 24 h. Cr(VI) adsorption was higher at high temperatures and low pH values, at equilibrium. The experimental data of Cr(VI) sorption fitted the isotherm models of Freundlich, Langmuir and Dubinin-Radushkevich for the studied concentration range (5 x 10^-4 to 4 x 10^-5 M). The adsorption mean energy was calculated by using the D-R adsorption isotherm in its lineal form. H⁰, S⁰ and G⁰ values proved that the Cr(VI) adsorption on calcium phosphate was an endothermic and spontaneous process. The obtained results indicate that calcium phosphate is an effective adsorbent to remove Cr(VI) anions from aqueous solutions, under the used experimental conditions. This material could be useful for the treatment of chromium industrial residues.

Keywords : calcium phosphate; chromate ions; adsorption; isotherms; thermodynamics parameters.

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