Extraction, separation and preconcentration of zirconium

Abstract

A sensitive and selective method for the solvent extraction, separation, transportation and microgram determination of zirconium(IV) with dibenzo-18-crown-6 is described. Zirconium(IV) is extracted with dibenzo-18-crown-6 from 0.1 M HCl and separated from hafnium. The extraction mechanism of zirconium from HCl media was investigated. The influence of the crown ether concentration, diverse ions and temperature on the distribution constant of zirconium have been examined. The extraction equilibrium constant (log βK′Zr) and distribution constant (Kex) were 16.50±0.05 and 108.5±0.10×10−13, respectively, in the dichloromethane. The values of enthalpy and standard energy were also obtained and the kinetics of zirconium transport is discussed. The system obeys Beer's law in the range of 0.15–3.60 ppm of zirconium(IV). The molar absorptivity is 3.0×104 l mol−1 cm−1 at 283 nm. The mixed zirconium-crown thiocynate extracted complex having the maximum absorbance at 450 nm with the molar absorptivity 1×104 l mol−1 cm−1. The zirconium-dibenzo-18-crown-6 complex extract in dichloromethane was directly inserted into plasma for ICP-AES measurement, which increases the sensitivity by about 30-folds. The zirconium is determined in presence of hafnium. The method is applied to trace determination of zirconium(lV) in standard samples and seawater samples.