Tasaki Tsutomu, Oshima Tatsuya, Baba Yoshinari
Department of Applied Chemistry, Faculty of Engineering, University of Miyazaki, 1-1Gakuen-Kibanadai Nishi, Miyazaki 889-2192, Japan.
Talanta. 2007 Sep 15;73(2):387-93. doi: 10.1016/j.talanta.2007.04.001. Epub 2007 Apr 7.
Two kinds of N-(6-alkylamido)-2-pyridine carboxylic acid with a pyridine moiety and a carboxylic acid as chelating ligands were newly synthesized for the selective extraction and the transport of copper(II) from aqueous solution. Liquid-liquid extraction was carried out to examine the extraction ability of extractants with metal ions. The selectivity for the metal ions with N-6-(2-ethylhexylamido)-2-pyridine carboxylic acid (EHPA) was in the following order: Cu(II)>>Zn(II) approximately Pb(II) approximately Ni(II) approximately Co(II)>Cd(II)>Mn(II). All metals tested in this study were selectively extracted at a lower pH by 2-3 units compared with commercial available alkyl carboxylic acids such as naphthenic acid and Versatic 10. The extraction equilibria of copper(II) were measured by a batchwise method at 303K with EHPA and N-6-(t-dodecylamido)-2-pyridinecarboxylic acid (t-DAPA). Copper(II) was extracted as a 1:2 complex according to the following reaction: Cu(2+)+2(HR )(2)=CuR(2)2HR +2H(+). The extraction equilibrium constant, K(ex) was evaluated and the values were found to be 1.13 and 0.31 for EHPA and t-DAPA, respectively. It was demonstrated that t-DAPA was very stable to be incorporated into a polymer inclusion membrane (PIM) consisting of cellulose triacetate (CTA) as a base polymer and 2-nitrophenyl octylether (NPOE) as a plasticizer. This novel PIM containing t-DAPA as a carrier exhibited an excellent copper(II) transport characteristic and a high selectivity for copper(II) over cadmium(II) from aqueous solution.
新合成了两种含有吡啶部分和羧酸作为螯合配体的N-(6-烷基酰胺基)-2-吡啶羧酸，用于从水溶液中选择性萃取和传输铜(II)。进行液-液萃取以研究萃取剂对金属离子的萃取能力。N-6-(2-乙基己酰胺基)-2-吡啶羧酸（EHPA）对金属离子的选择性顺序如下：Cu(II)>>Zn(II)≈Pb(II)≈Ni(II)≈Co(II)>Cd(II)>Mn(II)。与市售的烷基羧酸如环烷酸和Versatic 10相比，本研究中测试的所有金属在较低pH值下被选择性萃取，pH值低2 - 3个单位。在303K下用EHPA和N-6-(叔十二烷基酰胺基)-2-吡啶羧酸（t-DAPA）通过分批法测量铜(II)的萃取平衡。根据以下反应，铜(II)以1:2配合物形式被萃取：Cu(2+)+2(HR )(2)=CuR(2)2HR +2H(+)。评估了萃取平衡常数K(ex)，发现EHPA和t-DAPA的值分别为1.13和0.31。结果表明，t-DAPA非常稳定，可被纳入由三醋酸纤维素（CTA）作为基础聚合物和2-硝基苯基辛醚（NPOE）作为增塑剂组成的聚合物包合膜（PIM）中。这种含有t-DAPA作为载体的新型PIM表现出优异的铜(II)传输特性以及对水溶液中铜(II)相对于镉(II)的高选择性。
