Extraction Behavior of Metal Cations Using 8-Quinolinol as an Extractant in Cyclopentyl Methyl Ether

To date, many kinds of chelating extractants have been developed, however, many of the good extractants are insoluble in aliphatic solvents. In the present study, cyclopentyl methyl ether (CPME) was assessed as a solvent for extractants to develop new solvent extraction systems. Many of the extractants (100 mM) were soluble in CPME. The extraction behavior of metal ions using a typical chelating extractant, 8-quinolinol (HQ) in CPME, was studied. The extraction profiles of metal ions using HQ in CPME were similar to those in toluene, whereas metal ions were extracted using HQ in 1-octanol and chloroform under lower pH conditions. The extraction reaction of In(III) using HQ in CPME was confirmed by slope analysis. A 3 : 1 complex between HQ and In(III) was formed in CPME by a proton exchange reaction, and the extraction equilibrium constant was determined. In(III), extracted using HQ in CPME, was quantitatively recovered using mineral acids. From the results, CPME was found to be a potential alternative solvent to other toxic organic solvents for the development of a solvent extraction system.