Removal of Copper(II) from a Concentrated Sulphate Medium by Cloud Point Extraction Using an N,N'-Bis(salicylaldehyde) Ethylenediimine Di-Schiff Base Chelating Ligand

摘要

Various chelating ligands have been investigated for the cloud point extraction of several metal ions. However, limited studies on the use of the Schiff base ligands have been reported. In this work, cloud point extraction behavior of copper(II) with N,N'-bis(salicylaldehyde)Ethylenediimine Schiff base chelating ligand, (H2SALEN), was investigated in aqueous concentrated sulphate medium. The extraction process used is based on the formation of hydrophobic H2SA-LEN-copper(II) complexes that are solubilized in the micellar phase of a non-ionic surfactant, i.e. ethoxylated (9.5EO) tert-butylphenol. The copper(II) complexes are then extracted into the surfactant-rich phase above cloud point temperature. Different parameters affecting the extraction process of Cu(II), such as equilibrium pH, extractant concentration, and non-ionic surfactant concentration were explored. The extraction of Cu(II) was studied in the pH range of 2-11. The results obtained showed that it was profoundly influenced by the pH of the aqueous medium. The concentration factor, C_f, of about 17 with extraction efficiency of E % ≈ 100 was achieved. The stoichiometry of the extracted complex of copper(II) was ascertained by the Yoe-Jones method to give a composition of 1:1 (Cu:H2L). The optimum conditions of the extraction-removal have been established as the following: (1) 1.86 × 10~(-3) mol/L ligand; (2) 3 wt% surfactant; (3) pH of 8 (4) 0.5 mol/L Na2SO4 and (5) temperature of 60 °C.