Liquid-liquid extraction of Hf(IV) from nitric acid with dibutylsulfoxide in cyclohexane

Abstract

SummaryA liquid-liquid extraction method has been investigated for quantitative extraction of hafnium from 8 M HNO3using 50% di-n-butyl sulfoxide (DBSO) dissolved in cyclohexane. The extraction parameters such as nitric acid, DBSO and metal ion concentrations, equilibration time and temperature were optimized. The extraction was found to be independent of metal ion concentration in the range 4.5 × 10−4−4.5 × 10−2M and inversely dependent upon the temperature. Phosphate, fluoride and oxalate interfere seriously and have almost masked the extraction of Hf(IV) whereas, thiocyanate and bromide have greatly decreased (25–34%) the extraction. The stoichiometric composition of the extracted species was found to be Hf(NO3)4·2DBSO. Hafnium can be stripped from the organic phase by using 1 M HClO4. The proposed method allows the mutual separation of Hf(IV) and Zr(IV) using H2O2as masking agent for zirconium. The method has also been applied on synthetic mixtures of Hf and Zr for their separation and, the recovery was found to be quantitative.