Development of hydrazones as industrial extractants for rare metals

合成了烷基链上含有1 ~ 13个碳原子的水杨醛正链烷酰腙（SAAH或H2 L）和5-溴、3，5-二溴和5-硝基水杨醛乙酰腙（BSAH、DBSAH和NSAH，分别为SSAH或H2 L）。研究了在磷酸三丁酯（TBP）和高氯酸盐存在下，合成的腙对稀土离子（Ln^<3+>）（包括镨（III）、铕（III）和镱（III））在1，2-二氯乙烷中的萃取行为。结果表明，所有腙的萃取物均为（Ln^<3+>）（HL^-）_2（TBP）_3（ClO_4^-）。测定了腙的酸离解常数Ka、分配系数K_D和镧系元素络合物的萃取常数K_<ex>。SAAH的K_D值随烷基链上碳原子数的增加而增加，每增加一个碳原子，log K_D增加0.64。随着碳原子数的增加，K_D值也略有增加，但它们的K_D值随碳原子数的增加而增加，而随着碳原子数的增加，K_D值随碳原子数的增加而增加<ex>。 ...更多信息 另一方面，在水杨醛乙酰腙（SAH）苯环的3-和/或5-位引入吸电子的溴或硝基，不仅能有效地提高SAH的K_a值，而且能提高SAH的K_D值和<ex>镧系元素配合物的K_a值。本文研究了在磷酸三丁酯（TBP）和高氯酸盐存在下，水杨醛正辛酰腙（SOH或H_2L）的1，2-二氯乙烷溶液从水介质中萃取镱（Ⅲ）的动力学。的萃取率是一阶相对于镱（III）在水相和SOH在有机相中的浓度，相反的一阶相对于氢离子浓度和零和一阶相对于TBP在有机相中的浓度。根据有机相中的TBP浓度，两种机制对这种萃取起作用。一种是Yb^&lt;3+&gt;与HL^-在log[TBP]_ &lt; -0.95区域形成第一个络合物[Yb（HL）]^&lt;2+&gt;<org>为速率决定步骤，另一种是[Yb（TBP）]^&lt;3 +&gt;与HL^-在log [YBP]_ &gt;-0.85区域形成第一个络合物[Yb（HL）（TBP）]^&lt;2+&gt;<org>为速率决定步骤。计算了前一个反应的速率常数和活化参数，而后一个反应的速率常数和活化参数则无法确定。综合考虑上述三个常数，DBSAH是所合成的腙类萃取剂中对镧系元素最平衡、最易萃取的萃取剂。少

Salicylaldehyde n-alkanohydrazones (SAAH or H_2L)having 1 to 13 carbon atoms in their alkyl chains and 5-bromo,3,5-dibromo-and 5-nitrosalicyladehyde acetohydrazones (BSAH,DBSAH and NSAH, respectively, SSAH or H_2L) were synthesized. The extraction of lanthanoid ions (Ln^<3+>) including praseodymium(III), europium(III) and ytterbium(III) into 1,2-dichloroethane with the synthesized hydrazones in the presence of both tri-n-butylphosphate (TBP) and perchlorate has been investigated. The extracted species were (Ln^<3+>)(HL^-)_2(TBP)_3(ClO_4^-) for all the hydrazones. The acid dissociation constants, Ka, and the partition coefficients, K_D, of the hydrazones and the extraction constants, K_<ex>, of the lanthanoid complexes were determind. The K_D values of SAAH increased with an increase in the carbon number of the alkyl chain, the increment of log K_D being 0.64 per a carbon atom. The K_D values also increased slightly with an increase in the carbon number, but the K_<ex> values of their l … More anthanoid complexes were almost independent of the length of the alkyl chain, On the other hand, the introduction of electron-withdrawing bromo or nitro groups to the 3-and/or 5-position of the benzene ring in salicylaldehyde acetohydrazone (SAH) was very effective for increasing not only the K_a value of SAH but also its K_D value and the K_<ex> values of its lanthanoid complexes. The kinetics of the solvent extraction of ytterbium(III) from aqueous media with a 1,2-dichloroethane solution of salicyladehyde n-octanohydrazone(SOH or H_2L) in the presence of both tributylphosphate (TBP) and perchlorate have been studied at 25*0.1ﾟC and an ionic strength of 0.2. The rate of extraction was first-order with respect to the concentrations of ytterbium(III) in the aqueous phase and SOH in the organic phase, inversely first-order with respect to the hydrogen-ion concentration and zero- and first-order with respect to the TBP concentration in the organic phase. Two mechanisms operate for this extraction, depending on the TBP concentration in the organic phase. One is a mechanism in which the formation of the first complex, [Yb(HL)]^<2+>, between Yb^<3+> and HL^- in the region of log[TBP]_<org>< -0.95 becomes the rate-determining step, and the other is that in which the formation of the first complex, [Yb(HL)(TBP)]^<2+>, between [Yb(TBP)]^<3+> and HL^- in the region of log [YBP]_<org>>-0.85 is the rate-determining step. The rate constant and activation parameters for the former reaction were calculated, but those for the latter one could not be determined. Taking into consideration the above-mentioned three constants, of the synthesized hydrazones DBSAH was the most balanced and recommendable extractant for the lanthanoids. Less