Relationship Between Extraction of Arsenic via Ion Solvation and Hansen Solubility Parameters of Extractants

Extraction of As(III) from hydrochloric acid solution using various solvents on the basis of ion solvation has been reported, but a theoretical framework to describe the suitability of solvents for extraction has not been systematized. In this study, comprehensive extraction tests for As(III) using a variety of organic solvents were conducted to clarify the requirements for solvents to extract As(III). From the results of initial screening tests, various aromatics, ethers, and ketones were rated as candidates for the extraction of As(III) at high HCl concentrations, whereas aliphatic hydrocarbons were excluded. Many solvents showed high extraction capacity for As(III) to give organic fraction concentrations of 150 mM or higher. The logP value (P = partitioning coefficient between n-octanol and water) within a solvent class showed some correlation with extractability of As(III) but the correlation was invalid across solvent types. High correlation was shown between the Hansen solubility parameters of the solvents and As(III) extractability: Twenty of 22 solvents (90.9%) were appropriately classified as valid or invalid for the extraction of As(III) based on the Hansen sphere. 2-Nonanone was recommended as an ideal solvent for As(III) extraction because of its good balance between high extractability and its desirable physical properties for industrial operations. As(III) was quantitatively stripped from 2-nonanone into water with a concentration factor of 22.6.