Spectroscopic Determination of Thorium Based on Azophenylcalix[4]arene

Abstract

The work describes a new 1:1 complex of o-ester tetra azophenyl calix[4]arene (TEAC) with Th(IV) at pH 4-5 has found. The FTIR, H NMR, Raman spectra of calix[4]arene and its Th(IV) complex had also checked. Based on complex formation, a new method has been developed to determine thorium in monazite sand. The sand samples are decomposed by mixed acid (conc. H₂SO₄ and HF) in platinum crucible, after cooling, the residue was dissolved in dilute HCl and thorium is separated together with the lanthanides in the form of oxalate from zirconium, iron and the phosphate ion. The oxalate precipitate is dissolved in concentration nitric acid. After that, Th(IV) will be formed complex with o-ester tetra azophenyl calix[4]arene in acetate buffer solution. The absorbance of complex solution was measured at 520 nm against water as blank.