Solvent extraction mechanism and precipitation stripping of bismuth (III) in hydrochloric acid medium by tributyl phosphate

Tributyl phosphate (TBP) was employed for the Bi(III) extraction from hydrochloric acid medium. The effects of extraction time and material concentration were examined. The replacement mechanism between the anion (Cl − ) and TBP was proposed for extraction. The results show the species extracted into the organic phase were found to be mainly BiCl 3 · x TBP ( x =2 or 3). Thermodynamic parameters of the extraction reaction were obtained from the thermodynamics analysis, which illustrates that higher temperatures show a negative effect on the extraction. Extraction isotherm was obtained with 2.16 mol/L TBP for a typical solution containing 0.1 mol/L of bismuth and 1.0 mol/L of hydrochloric acid. About 98.5 % of bismuth has been extracted from the leaching solution under the optimum condition. Moreover, oxalate was explored as a precipitation stripping agent for BiCl 3 · x TBP ( x =2 or 3) complexes, by which Bi(III) was stripped in the form of Bi 2 (C 2 O 4 ) 3 ·7H 2 O. A stripping efficiency of 99.3% was obtained in only one stage at the phase ratio of 1 and TBP also could be recycled. Therefore, the method is an efficient, effective and highly selective approach to extract Bi(III) and to recover metal bismuth.