YE Ling, ZHANG Jing-yang, XIAO Zi-jing
(College of Material Science and Engineering, Huaqiao University, Xiamen 361021, China)

Abstract: Ability of metal cation adsorption on montmorillonite depends on electrokinetic properties of colloid suspension. Values of ζ-potential have a prominent effect on its adsorptive behaviour. This study are focuses on the relationship between montmorillonite ζ-potential and adsorption capacity for Cr3+, and the adsorption behaviour of Cr3+ and its chelate cations [Cr(phen)3]3+, forming with 1,10-phenanthroline, from aqueous solutions on montmorillonite. Batch adsorption studies were carried out with various Cr3+ concentrations, pH, agitation time and temperature. The results show that the adsorption capacity of Cr3+ on montmorillonite displayed obvious increases in the presence of 1,10-phenanthroline. The adsorption effect for [Cr(phen)3]3+ on montmorillonite includes electrostatic attraction and intermolecular hydrogen bonds; the former interaction is the result of permanent-charge and [Cr(phen)3]3+cations, and the latter interaction is the result of Si-OH hydroxyl and 1,10-phenanthroline. The equilibrium conversion ratio of adsorption reaction increases when [Cr(phen)3]3+ is adsorbed instead of Cr3+, and the adsorption of [Cr(phen)3]3+ is pH independent. It was also found that the kinetics of Cr3+ and [Cr(phen)3]3+ uptake by montmorillonite followed the pseudo-second-order adsorption mechanism. The suitability of Langmuir and Freundlich adsorption models to the equilibrium data was investigated. The adsorption of Cr3+ and [Cr(phen)3]3+ are all well described by the Langmuir isotherm model. Moreover, the results suggest that the adsorptions of Cr3+ and [Cr(phen)3]3+on montmorillonite are both spontaneous, endothermic and more disorderly.

Keywords: montmorillonite; Cr3+; chelate; electrokinetic properties; adsorption

Email: ylj@hqu.edu.cn

ACTA MINERALOGICA SINICA Vol. 35, No. 2, 2015, Page 122-126