Indium Research Paper

Abstract A simple, precise and accurate solvent extraction method is described for the separation and estimation of Indium in geological materials. Solvent extraction of Indium from 6 M HCl medium using tri-n-butyl phosphate, selectively separates Indium from accompanying elements in different type of geological samples. Acid hydrolysis of Nb/Ta samples separates Indium from major matrix elements like Nb and Ta and the remaining elements do not influence the selective extraction and preconcentration of In and its subsequent determination by ICP-AES or flame AAS. The silica rich geological samples are decomposed by HF-H2SO4-HCl treatment followed by dissolution in 6M HCl before applying solvent extraction procedure. In Nb/Ta type of samples, Indium was separated from Nb and Ta by acid hydrolysis, involving fusion with Na2O2, dissolution in HCl followed by NH4OH precipitation and hydrolysis in HCl. The oxychloride precipitates of Nb and Ta are filtered off and subjected to solvent extraction using TBP. The proposed method has been applied to some international reference standards (IGS-33 and ASK-3) and to some Nb/Ta type samples and the results are compared by ICP-AES as well flame AAS techniques. The method is simple, rapid and accurate showing a relative standard deviation of 2% (at 170 μg/g) to 7.0% (at 16 μg/g ) and the method can be applied down to 1 μg/g and above.
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Key words : Indium; Geological materials; Niobate-Tantalate; acid hydrolysis; solvent extraction; ICP-AES.

INTRODUCTION Indium is a highly dispersed element in nature with a crustal abundance of 0.1 μg/g(1). Though indium is present in minerals like Jallindite In(OH)3, Indite FeIn2s4, Roquesite CuInS2, Sakurayite (CuZnFe)3InS4, (2,3) their occurances are very rare and they are not important as a source of indium. Due to the similarity in the

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