Solvent Extraction of Tellurium from Chloride Solutions Using Tri-n-butyl Phosphate: Conditions and Thermodynamic Data

The extractive separation of tellurium (IV) from hydrochloric acid media with tri-n-butyl phosphate (TBP) in kerosene was investigated. The dependence on the extraction of tellurium species, concentrations of tellurium and TBP, extraction time and stage, organic/aqueous ratio, and interferences from coexist metallic ions were examined and are discussed. Besides, the stripping agent and stripping time were also studied. It was found that the extraction reaction corresponds to the neutral complex formation mechanism and the extracted species is TeCl(4) ·3TBP and that the extraction process is exothermic. The thermodynamic parameters of enthalpy (ΔH), entropy (ΔS), and free energy (ΔG) of the extraction process were evaluated at −26.2 kJ·mol(−1), −65.6 J·mol(−1) ·K(−1), and −7.0 kJ·mol(−1), respectively at 293 K.