Fundamentals of the Use of Mixed Solvents in Solvent Extraction of Metal Ions

选择了铜(II)、苯甲酸和正辛醇-苯或2-辛酮-苯混合溶剂组成的萃取体系，研究了混合溶剂对金属萃取的影响。在分析萃取剂对金属离子的萃取平衡时，必须了解萃取剂的分配情况。测定了苯甲酸在正辛醇-苯和2-辛酮-苯混合溶剂体系中的分配常数和二聚常数。用1个1-辛醇或2-辛酮分子对单体苯甲酸进行溶剂化反应，定量解释了单体苯甲酸在有机相中分配常数的增大和二聚常数减小的原因。但是，在正辛醇-苯混合溶剂的较高正辛醇区，分配常数和二聚常数被发现符合BECO…比单体酸被1-辛醇分子溶剂化所预测的要小得多。这是由于在混合溶剂中，随着正辛醇含量的增加，水的浓度增加，导致单体苯甲酸的水合作用。用与分析苯甲酸分配平衡相同的混合比例的1-辛醇-苯和2-辛酮-苯混合溶剂，用苯甲酸进行了铜(II)的萃取。单体和二聚体苯甲酸铜(II)在各个萃取体系中起主要作用。在目前的混合溶剂体系中，CuA_2(主要单体萃取物)与HA(单体苯甲酸)的分配常数之间存在如下关系式：Kd，CuA_2=CKD，HA^2，其中C是与各相似系列溶剂对应的某一常数。此外，还证明了目前使用的一定组成的混合溶剂对苯甲酸萃取铜(II)的效果优于氯仿。较少

The solvent extraction systems, which consist of copper (II), benzoic acid and 1-octanol-benzene or 2-octanone-benzene mixed solvents, were selected for the purpose of studying the effects of mixed solvents on the solvent extraction of metals. In the analysis of the extraction equilibrium on the extraction of metal ion with an extracting reagent, it is indispensable to have information about the partition of the extracting agent. The partition and dimerization constants ofbenzoic acid have been determined in the 1-octanol-benzene and 2-octanone-benzene mixed solvent systems. The increase in the partition constant of monomeric benzoic acid and the decrease in the decrease in the dimerization constant of the acid in the organic phase were quantitatively explained taking into account solvation of monomeric benzoic acid by one 1-octanol or 2-octanone molecules. But, in a higher 1-octanol region of 1-octanol-benzene mixed solvents, the partition and dimerization constants were found to beco … More me smaller than those predicted by solvation of the monomeric acid by one 1-octanol molecule. This is attributable to hydration of the monomeric benzoic acid because of increasing the concentration of water with increasing content of 1-octanol in the mixed solventsBy using the same 1-octanol-benzene and 2-octanone -benzene mixed solvents with a wide variety of mixing ratio as those used for the analysis of the partition equilibrium of benzoic acid, the extraction of copper (II) with benzoic acid was carried out. The monomeric and dimeric copper (II) benzoates were found to be responsible for the every extraction systems. In the present mixed solvent systems, the following relation between the partition constants of CuA_2 (main monomeric extracted species) and HA (monomeric benzoic acid) was found to be hold : KD,CuA_2=CKD,HA^2, which C is the certain constant corresponded to the each similar series of solvents. In addition, it has been proved that the present mixed solvents with a certain composition are superior to chloroform in the extraction of copper (II) with benzoic acid. Less