A Comparative Study of Extraction of Selenium(IV) Using Various Organic Solvents in Hydrochloric Acid Media

To date, suitable organic solvents for the extraction of tetravalent selenium (Se(IV)) in highly concentrated hydrochloric acid have not been clarified systematically. In this study, the extraction of Se(IV) using various organic solvents was compared. Se(IV) was extracted from 8.0 mol/dm³ hydrochloric acid using various ketones. Se(IV) extraction using ethers was lower, while that using hydrocarbons was negligible. The correlation between the extraction and logP value of solvents was small, however, the extraction using a hydrophobic dicyclohexyl ketone was lower. The extractability of Se(IV) by most solvents can be classified with the Hansen solubility parameters of the solvents. However, Se(IV) extracted by 2-nonanone was not stripped by contact with fresh aqueous solutions containing HCl, HNO₃, NaOH, or EDTA.