Three-Liquid-Phase Extraction: A New Approach for Simultaneous Enrichment and Separation of Cr(III) and Cr(VI)

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• 作者：Keng Xie ; Kun Huang ; Liangrong Yang ; Pinhua Yu ; Huizhou Liu
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2011
• 出版时间：November 16, 2011
• 年：2011
• 卷：50
• 期：22
• 页码：12767-12773
• 全文大小：930K
• 年卷期：v.50,no.22(November 16, 2011)
• ISSN：1520-5045

文摘

A novel and simple three-liquid-phase extraction (TLPE) approach was developed for the simultaneous removal and separation of Cr(III) and Cr(VI) from aqueous solutions. The proposed three-liquid-phase system (TLPS) consists of di(2-ethylhexyl)phosphoric acid (D2EHPA), poly(ethylene glycol) (PEG) with a molecular weight of 2000, and (NH₄)₂SO₄. The effects of various factors including the aqueous solution pH, amounts of (NH₄)₂SO₄ and PEG, initial chromium amount, D2EHPA concentration, phase-mixing time, and diluent on the three-phase partitioning behavior of Cr(III) and Cr(VI) were evaluated. The distribution behavior of the two oxidation states of chromium was found to be highly pH-dependent. Cr(III) preferred the D2EHPA-rich top phase through a cation-exchange reaction, whereas Cr(VI) was enriched in the PEG-rich middle phase through ion-pair formation. By appropriate selection of the extraction conditions, nearly all of the Cr(III) was extracted into the D2EHPA top phase, and more than 90% of the Cr(VI) was transferred into the PEG-rich middle phase within 5 min. The present work highlights the possibility of using the TLPE approach for the extraction and separation of two different oxidation states of metal ions, such as Cr(III) and Cr(VI), in a single extraction step.