A Spectroscopic Study of Th(IV) Ion in Aqueous Medium and Its Analytical Importance

Abstract

When thorium nitrate dissolves in a water, it is known that hydrolysis of Th4+ occurs at pH around 3 leading to the formation of [Th(OH)]3+,[Th(OH)2]2+, [Th(OH)3]+, [Th(OH)4] and some dimeric and polymeric species of Th4+ ion. To study electronic transition properties these species measured absorbance properties of concentration range from 1x10-5M to 10-9M Th4+. The narrow working range of Th(IV) ion lies between 7x10-6 M to 5x10-7M above 7x10-6 M and below 5x10-7M Th4+ concentration no absorbance peak in the region of 190nm to 400nm. This work describes here out of four tetravalent ions present in the group IVB i.e., Ti4+, Zr4+, Hf4+ only Th4+ is giving UV absorbance peak in the region of 205nm. This evidence shows that Th4+ is belong to actinide series not in transition series. Moreover, this peak is absorbed only in water medium and does not exhibits any electronic transition properties in other solvents like methanol (CH3OH), ethanol(C2H5OH), acetone (CH3COCH3), dimethylsulphoxide (CH3CSCH3), diethyl ether(C2H5)2O and tetrahydrofurane (C5H4O). Theoretically, the structures and absorption spectra of all possible species of Th(IV) hydrolysis were calculated using Gaussian 03 programme and B3LYP density functional method with the SDD basis set in ground state and TD-SCF excited state.