Analytical Sciences

Hexavalent Chromium Recovery by Liquid-Liquid Extraction with Tributylphosphate from Acidic Chloride Media

A. OUEJHANI,*^,** M. DACHRAOUI,* G. LALLEVE,** and J. F. FAUVARQUE**

*Laboratoire de Chimie Analytique et Electrochimie, Faculte des Sciences de Tunis, Departement de Chimie Campus Universitaire, 1060 Tunis, Tunisie
**Laboratoire d'Electrochimie Industrielle, Conservatoire National des Arts et Metiers, 75003 Paris, France

A method is introduced for recuperation of chromium(VI) in water samples by liquid-liquid extraction with tributylphosphate PO(C₄H₉O)₃ (TBP) from acidic chloride media. The optimum conditions for quantitative extraction of Cr(VI) were evaluated by varying the experimental parameters, such as the shaking period, the pH of the aqueous phase, the hydrochloric acid concentration, the hydrogen and chloride ion concentrations, the extractant concentration and the ratio of aqueous-to-organic phase. The probable extracted species of hexavalent chromium in organic phase, deduced from log-log plots, were H₂CrO₄ in acid media in absence of chloride and HCrO₃Cl in acidic chloride media. Chromium(VI) was found to be extracted with tributylphosphate from acidic chloride media according to the following reaction: HCrO₄^-_(aq) + 2H⁺_(aq) + Cl^-_(aq) + 2TBP_(org) ↔ [HCrO₃Cl, 2TBP]_(org) + H₂O_(aq). Since the tributylphosphate (TBP) exhibited a high selectivity for chromium(VI), this method can be applicable to the extraction and the determination of chromium in both oxidation states {Cr(VI) and Cr(III)} in water samples.

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