PH-DEPENDENCE OF CARBOXYLIC AND MINERAL ACID-EXTRACTION BY AMINE-BASED EXTRACTANTS - EFFECTS OF PK(A), AMINE BASICITY, AND DILUENT PROPERTIES
PH-DEPENDENCE OF CARBOXYLIC AND MINERAL ACID-EXTRACTION BY AMINE-BASED EXTRACTANTS - EFFECTS OF PK(A), AMINE BASICITY, AND DILUENT PROPERTIES
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DOI：
10.1021/ie00044a030
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发表时间：
1995-05-01
影响因子：
4.2
通讯作者：
CANARI, R
中科院分区：
文献类型：
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作者：
EYAL, AM;CANARI, R
萃取机理很大程度上取决于萃取剂的酸碱性质，也取决于萃取酸的酸碱性质。对于碱度与被萃取酸的阴离子相似或更高的胺，萃取是由离子对形成控制的。只有在弱碱提取弱酸时，未离解酸的氢键才变得重要。萃取机理决定了各种参数的影响。因此，在通过离子对形成萃取的胺的pK(A)附近，萃取度对pH最敏感。然而，氢键萃取在酸的pK(A)附近最为敏感。极性稀释剂和质子型稀释剂通过形成离子对促进萃取，但可能对氢键没有影响，甚至阻碍氢键。在低pH条件下，离子对萃取法提取较强的酸，而氢键能更有效地提取较弱的酸。阐明萃取剂的萃取机理及其对萃取酸性质和pH的依赖关系，有助于设计高效、选择性的萃取剂。
Extraction mechanism strongly depends on the acid-base properties of the extractant as well as on those of the extracted acid. For amines of basicity similar to that of the anion of the extracted acid, or higher, extraction is governed by ion-pair formation. H-bonding of undissociated acid becomes important only for extraction of weak acids by weak bases. Extraction mechanism determines the effect of various parameters. Thus, the degree of extraction is most sensitive to pH at about the pK(a), of the amine for extraction through ion-pair formation. Extraction by H-bonding, however, is most sensitive at about the pK(a), of the acid. Polar and protic diluents enhance extraction through ion-pair formation, but may have no effect on H-bonding or even hinder it. Extraction through ion-pair formation prefers stronger acids at low pH while H-bonding extracts weaker acids more efficiently. Clarification of the extraction mechanism and its dependence on extracted acid properties and on the pH provide for designing extractants of high efficiency and selectivity.