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Effect of chromium speciation on its sorption mechanism onto grape stalks entrapped into alginate beads

Sorption of Cr(III) and Cr(VI) ions onto 2% grape stalk (GS) powder entrapped in a biopolymeric gel matrix of calcium alginate (CA) has been investigated and a mechanism for the retention of both, Cr(VI) and Cr(III) is proposed. Protons were found to be consumed in Cr(VI) sorption/reduction and to compete with Cr(III) for the sorbent active sites. Isotherm equilibrium was modelled according to Langmuir equation: maximum capacity was found to be 6.4 and 3.6 mg g−1 for Cr(III) and Cr(VI), respectively. The important Ca2+ release observed when Cr(III) is sorbed indicates that ion exchange is the main mechanism involved at concentrations lower than 200 mg L−1 while other mechanisms such as microprecipitation or coordination might take place for higher initial concentrations. In the case of Cr(VI), the sorption mechanism is based on the reduction to Cr(III) promoted by both protons and the functional groups on the GS surface; this reduction-formed Cr(III) is retained by the alginate gel matrix and by microprecipitation onto the surface of GS particles. ESR and SEM-EDX were used to identify chromium species sorbed on the solid phase. Results from this study suggest that GS entrapped in CA gel beads is an effective sorbent for both, Cr(III) and Cr(VI) removal from aqueous solutions

Arabian Journal of Chemistry, 2017, vol. 10, suplement 1, p. S1293-S1302

Elsevier

Autor: Escudero Oñate, Carlos
Fiol Santaló, Núria
Villaescusa Gil, Isabel
Bollinger, Jean Claude
Data: 1 febrer 2017
Resum: Sorption of Cr(III) and Cr(VI) ions onto 2% grape stalk (GS) powder entrapped in a biopolymeric gel matrix of calcium alginate (CA) has been investigated and a mechanism for the retention of both, Cr(VI) and Cr(III) is proposed. Protons were found to be consumed in Cr(VI) sorption/reduction and to compete with Cr(III) for the sorbent active sites. Isotherm equilibrium was modelled according to Langmuir equation: maximum capacity was found to be 6.4 and 3.6 mg g−1 for Cr(III) and Cr(VI), respectively. The important Ca2+ release observed when Cr(III) is sorbed indicates that ion exchange is the main mechanism involved at concentrations lower than 200 mg L−1 while other mechanisms such as microprecipitation or coordination might take place for higher initial concentrations. In the case of Cr(VI), the sorption mechanism is based on the reduction to Cr(III) promoted by both protons and the functional groups on the GS surface; this reduction-formed Cr(III) is retained by the alginate gel matrix and by microprecipitation onto the surface of GS particles. ESR and SEM-EDX were used to identify chromium species sorbed on the solid phase. Results from this study suggest that GS entrapped in CA gel beads is an effective sorbent for both, Cr(III) and Cr(VI) removal from aqueous solutions
Format: application/pdf
ISSN: 1878-5352
Accés al document: http://hdl.handle.net/10256/14146
Llenguatge: eng
Editor: Elsevier
Col·lecció: Reproducció digital del document publicat a: http://dx.doi.org/10.1016/j.arabjc.2013.03.011
Articles publicats (D-EQATA)
És part de: Arabian Journal of Chemistry, 2017, vol. 10, suplement 1, p. S1293-S1302
Drets: Attribution-NonCommercial-NoDerivs 3.0 Spain
URI Drets: http://creativecommons.org/licenses/by-nc-nd/3.0/es/
Matèria: Metalls -- Absorció i adsorció
Metals -- Absorption and adsorption
Crom
Chromium
Títol: Effect of chromium speciation on its sorption mechanism onto grape stalks entrapped into alginate beads
Tipus: info:eu-repo/semantics/article
Repositori: DUGiDocs

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