Extraction of Metal Ions Using a Calix[4]arene Carboxylic Acid Derivative in Aromatic Ethers

If calixarenes can be dissolved in a relatively safe non-halogen solvent, they can be used in a liquid-liquid extraction process suitable for mass processing. In the present study, extraction behavior of metal ions using a calix[4]arene carboxylic acid derivative (tOct[4]CH2COOH) dissolved in aromatic ethers was investigated. The solubility of tOct[4]CH2COOH in aromatic ethers decreases with increase of the length of aliphatic side chain of the ethers. The solubility of tOct[4]CH2COOH in 1-butoxybenzene (BB) was 28.0 mmol/L, which is smaller than that in chloroform but is higher than those in hexane and toluene. Divalent metal ions Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Pb(II) were extracted using tOct[4]CH2COOH in BB through proton exchange reaction at similar pH range in toluene, which is higher than that in chloroform. The extraction reaction of Cu(II) using tOct[4]CH2COOH in BB was determined by slope analysis and loading test. The stoichiometry between tOct[4]CH2COOH and Cu(II) was 2:1.