Structural properties of the inner coordination sphere of indium chloride complexes in organic and aqueous solutions

Abstract

The nature of the inner coordination sphere of In(3+) present in both the organic and aqueous solutions during the solvent extraction of In(3+) from an aqueous HCl solution with tri-n-octyl amine (TOA) was investigated by In K-edge XAFS. This information was then used to clarify the details of the extraction properties of indium chloride anion complexes with TOA. In aqueous HCl solution (0.1-10 M), In(3+) exists as octahedral anion complexes, [InCln(H2O)6-n](3-n) (n ≥ 4); the [InCl6](3-) complex is dominant at 10 M HCl. The extraction of In(3+) from HCl solution with TOA was performed using two kinds of diluents: nitrobenzene (NB) or n-dodecane (DD), which contained 20 vol% of 2-ethylhexanol as an additive. The stoichiometric composition of the extracted complexes, which is estimated from the distribution ratios of In(3+), is affected by the diluents and the HCl concentration of the aqueous phase; the apparent values of TOA/In(3+) in the extracted complex are 3 for DD-1 M HCl (diluent-aqueous phase) and DD-5 M HCl, 2 for NB-1 M HCl and NB-5 M HCl, and 1 for NB-10 M HCl. The EXAFS analysis of these extracted complexes shows that the In(3+) has ∼4 Cl(-) at ∼2.336 Å and no H2O in the inner coordination sphere; additionally, the shape of the XANES suggests that their coordination geometry is tetrahedral. Therefore, the same tetrahedral [InCl4](-) complex is formed during the extraction in spite of the variation in the stoichiometric composition (TOA/In(3+) = 1-3) of the extracted complexes.

Speciation of indium(iii) chloro complexes in the solvent extraction process from chloride aqueous solutions to ionic liquids

“…10,[34][35][36][37] Also, knowledge of the speciation of metals in the aqueous phase is required to allow proper selection of extractants, since the extractability of metal ions depends strongly upon the structure of metal complexes in the aqueous phase. 38 Moreover, the speciation of the metal ions in the aqueous and ionic liquid phase provides valuable information regarding the extraction mechanism.…”

Chemical Thermodynamics and Calculation of Parameters of Ionic Equilibria of Indium(III) in Perchlorate, Chloride and Sulphate Aqueous Solutions

“…Так, например, выявлены систематические ошибки при определении среднего числа связанных с центральным ионом In 3+ анионов Clметодом EXAFS в публикациях 2014-2017 гг. [3,7]. Наиболее надежными являются данные, полученные потенциометрическим и ионообменным методами.…”

“…Индий -стратегически важный редкий и рассеянный металл, и его химия и технология активно обсуждаются в литературе последних лет [1][2][3][4][5][6][7]. Знание химического состояния индия в растворах различного состава необходимо для решения широкого круга научных и прикладных задач, в том числе, для расчета равновесий, определения состава комплексов, образующихся при экстракции в органической фазе, для оптимизации условий получения материалов и т. п.…”

“…Таким образом, возникает задача критического анализа и обобщения всего накопленного материала по химии и термодинамике водных растворов индия(III). Особое значение приобретает сопоставление данных, полученных в разных лабораториях и независимыми методами [3,7,13,21].…”

Separation Of Radioisotope 113mIn Using Column Chromatography Based on Silica Gel Matrix

“…The chemical form of 113m In in RG 113 Sn/ 113m In eluate is In 3+ at low chloride concentration. While higher chloride concentrations, it formed complex chlorides such as InCl 2+ , and even InCl 2+ on a stronger chloride concentration converted to anionic form InCl 4- (Abdel-Halim, 2002;Narita et al, 2014).…”