Distribution Thermodynamics of Metal Complexes in Micelles of Nonionic Surfactants.

Abstract

The complexation of cobalt(II), nickel(II), copper(II), and zinc(II) with thiocyanate ions has been studied in micellar solutions of nonionic surfactant Triton X-100 by titration spectrophotometry and calorimetry. The complexation has been also studied by varying length of POE (polyoxyethylene) chain. With regard to Co(II), the [CO(NCS) 4 ] 2- , which hardly forms in aqueous phase, is extensively formed in micelles. With Zn(II), the [Zn(NCS) 3 ] - and [Zn(NCS) 4 ] 2- are formed in micelles. With Ni(II), no complexation occurs in micelles. In the case of Cu(II), the formation of [Cu(NCS) 2 ] is concluded in both micelles and aqueous phase. The complexation behavior of [Co(NCS) 4 ] 2- and [CU(NCS) 2 ] depends significantly on the length of POE chain, suggesting that these complexes exist both in the relatively hydrophilic POE site and hydrophobic core site.