Adsorption mechanisms of metal cations from water on an oxidized carbon surface
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Moreno Castilla, Carlos; Álvarez Merino, Miguel Ángel; Pastrana Martínez, Luisa María; López-Ramón, M.V.Editorial
Elsevier
Date
2010-05-15Referencia bibliográfica
Journal of Colloid and Interface Science Volume 345, Issue 2, 2010, Pages 461-466
Sponsorship
Authors are grateful to MEC and FEDER project CTQ2007-67792-C02-02 and Junta de Andalucía project RNM 547 for financial support. LMPM acknowledges receipt of MEC pre-doctoral fellowshipAbstract
Adsorption of Cr(III), Mn(II), Cu(II) and Zn(II) on an oxidized activated carbon cloth was studied. Its surface chemistry was characterized by potentiometric titration. This technique revealed the amount of surface oxygen functionalities and their acidity constant distribution. The acidity constant range involved in the metal cation adsorption was obtained from this distribution. Metal cation adsorption increased with higher adsorption temperature due to the increase in the negative surface charge of the oxidized activated carbon. Adsorption was by proton exchange and the number, amount and strength of the surface acid groups involved could be obtained. The proton exchange was by an inner-sphere or outer-sphere surface metal complex formation mechanism. In the case of divalent cation adsorption, the increase in temperature changed the adsorption mechanism from outer-sphere to inner-sphere. However, the adsorption mechanism of Cr(III) was outer-sphere and independent of temperature. Adsorption capacity augmented with the increase in the charge-to-size ratio of the hexa-aquo cations. In addition, the adsorption capacity of divalent cations increased with the rise in stability of the surface metal complex formed.