On an Expression of Extraction Constants without the Interfacial Equilibrium-Potential Differences for the Extraction of Univalent and Divalent Metal Picrates by Crown Ethers into 1,2-Dichloroethane and Nitrobenzene

Yoshihiro Kudo,Shoichi Katsuta

doi:10.4236/ajac.2015.64034

Abstract

An idea on interfacial equilibrium-potential differences () which are generated for the extraction of univalent metal picrate (MPic) and divalent ones (MPic2) by crown ethers (L) into high-polar diluents was improved. These potentials were clarified with some experimental extraction-data reported before on the M = Ag(I), Ca(II), Sr(II) and Ba(II) extraction with 18-crown-6 ether (18C6) and benzo-18C6 into 1,2-dichloroethane (DCE) and nitrobenzene (NB). Consequently, it was demonstrated that the values from the extraction-experimentally obtained logKD,Pic ones are in agreement with or close to those calculated from charge balance equations in many cases, where the symbol, KD,Pic, denotes an individual distribution constant of Pic﹣ into the DCE or NB phase. Also, it was experimentally shown that extraction constants based on the overall extraction equilibria do not virtually contain the terms in their functional expressions.

Highlights

Univalent and divalent metal picrates (MPicz, z = 1& 2), such as alkali and alkaline-earth metal ones, have been extracted by crown compounds (L) into the high-polar diluents, such as 1,2-dichloethane (DCE), dichloromethane and nitrobenzene (NB) [1]-[5]
The logKD,Pic values were −0.94 [2] for the PbPic2 extraction with 18-crown-6 ether (18C6), −1.34 [7] for the SrPic2 one with benzo-18C6 (B18C6) into NB, −2.46 [3] for the AgPic one with benzo-15-crown-5 ether, −1.89 [2] for the PbPic2 one with 18C6 and −4.35 [6] for the CdPic2 one with 18C6 into DCE
Their values have changed over experimental errors with combinations of MPicz and L

Summary

Introduction

Univalent and divalent metal picrates (MPicz , z = 1& 2) , such as alkali and alkaline-earth metal ones, have been extracted by crown compounds (L) into the high-polar diluents, such as 1,2-dichloethane (DCE), dichloromethane and nitrobenzene (NB) [1]-[5] In such high-polar diluents, an extracted ion-pair complex, MLPicz, dissociates MLz+ and zPic− [1]-[3] [6]. In order to solve the above two contradictions, namely the differences of KD,A caused by experimental conditions of extraction and the contradiction based on the thermodynamic cycles [3] [7], we proposed another expression without ∆φeq of the extraction constants, Kex± and Kex2±. In course of clarifying this expression, some experimentally-determined constants [3] [7], such as Kex±, an individual distribution constant (KD,ML) of the complex ion ML2+ into the NB phase and that of AgL+ into DCE, were reproduced by calculation.

Theory

Results and Discussion

For Applications to Other Extraction Systems

Conclusion