Comparative Study of the Adsorption Selectivity of Cr(VI) onto Cationic Hydrogels with Different Functional Groups

Tang, Samuel C. N.; Lo, Irene M. C.; Mak, Mark S. H.

Comparative Study of the Adsorption Selectivity of Cr(VI) onto Cationic Hydrogels with Different Functional Groups

2012

Tang, Samuel C. N. | Lo, Irene M. C. | Mak, Mark S. H.

Two types of hydrogels with different functional groups, trimethylamine on quaternary ammonium and dimethylethoxyamine on quaternary ammonium, were synthesized. Type 1 and type 2 hydrogels were characterized with Fourier transform infrared, X-ray photoelectron spectroscopy and zeta potential analysis. The anion selectivity of these two hydrogels was investigated. The surface charges of the type 2 hydrogel were lower than those of type 1, probably because of the presence of the hydroxyl group in the ethoxy group. The Cr(VI) removal capacity of type 2 hydrogel was, therefore, less than that of type 1 hydrogel, although their adsorption rates were similar. The anion selectivity of the hydrogels was found to have a similar order: Cr(VI) > sulphate > bromide > As(V). Under the co-presence of Cr(VI) and sulphate conditions, type 2 hydrogel shows a higher selectivity towards Cr(VI). The higher hydrophobicity was caused by the presence of the ethoxy group on the quaternary ammonium in type 2 hydrogel and thus increased in selectivity towards monovalent ions (i.e. HCrO 4 − ). In addition, the hydrogels have a high reusability. Compared with type 1 hydrogel, type 2 hydrogel has an advantage for applications in Cr(VI) removal and recovery processes.

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