Selectivity in the Extraction of Copper(II) with a New Alkylated 8-Quinolinol Derivative with a Nitrophenylazo Substituent

Abstract

The extraction behavior of Mn^II, Fe^III, Co^II, Ni^II, Cu^II, Zn^II, Ga^III, and Cd^II was studied with a new chelating extractant, 5-(4-nitrophenylazo)-7-(4-ethyl-1-methyloctyl)-8-quinolinol (HNEQ), in chloroform. HNEQ exhibits a much higher extractability for Co^II, Cu^II, Zn^II, and Cd^II than 8-quinolinol. Especially, Cu^II was quantitatively extracted with 0.001mol dm^-3 of HNEQ at such a low pH as 2.0 within 15min, and was readily separated from the other metal(II, III) ions studied. From equilibrium studies, the extracted Cu^II-HNEQ chelate was ascertained to be Cu(NEQ)₂. The extraction constant (logK_ex) was determined to be 4.25, which was much larger than those for 7-(4-ethyl-1-methyloctyl)-8-quinolinol (Kelex 100) and 8-quinolinol.