A novel polydentate Schiff base extractant, N, N′-bis(salicylideneaminoethyl)amine (H 2 L), was successfully used in a cloud point extraction of copper(II) from aqueous sulfate solutions. The extraction process is based on the formation of a hydrophobic complex of copper(II)-H 2 L, which is subsequently extracted into the nonionic surfactant p-octylpolyethyleneglycolphenylether (Triton X-100) rich phase at a temperature above the cloud point temperature (CPT). The phase diagrams of the binary system, water-surfactant (Triton X-100), and the ternary systems, water-surfactant-salt (Na 2 SO 4 ), were determined. The effects of the main experimental parameters such as pH, extractant concentration, and nonionic surfactant concentration on the extraction behavior of copper(II) with N,N′-bis(salicylideneaminoethyl)amine were studied. The percentage extraction was found to be significantly dependent on the aqueous solution pH. The extraction of copper(II) was observed in the pH range of (3 to 11). The stoichiometry of the extracted species of copper(II) was ascertained by the Yoe-Jones mole ratio method to have a composition of 1:1 (Cu:H 2 L). The optimum conditions of the extraction of copper(II) have been established as the following: (1) 2 • 10 -3 mol • L -1 extractant; (2) 5 % (by weight) surfactant; (3) pH of 9; (4) 0.49 mol • L -1 Na 2 SO 4 ; and (5) temperature of 65 °C.

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 0 -bis(salicylaldehyde)Ethylenediimine Schiff base chelating ligand, (H 2 SALEN), was investigated in aqueous concentrated sulphate medium. The extraction process used is based on the formation of hydrophobic H 2 SA-LEN-copper(II) complexes that are solubilized in the micellar phase of a non-ionic surfactant, i.e. ethoxylated (9.5EO) tertbutylphenol. 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:H 2 L). The optimum conditions of the extraction-removal have been established as the following: (1) 1.86 9 10 -3 mol/L ligand; (2) 3 wt% surfactant; (3) pH of 8 (4) 0.5 mol/L Na 2 SO 4 and (5) temperature of 60°C.

A novel series of four Schiff base amphiphiles derived from 3-mercapto-1,2,4-triazole and different alkyl chains were successfully prepared by a new synthetic three-step method. The chemical structures of the different ligands were characterized by elemental analysis, FT-IR spectroscopy, 1 H-NMR and 13 C-NMR spectra. The effect of the chain length on the solution behavior of the amphiphilic ligands were studied, in both homogeneous and heterogeneous systems, using pH-metric and spectrophotometric methods. Based on the electronic spectroscopy data, some parameters governing their surfactant properties, such as the critical micelle concentration (CMC), the micellization free energy (DG mic ) and the hydrophilic-lipophilic balance (HLB) were evaluated in chloroform and discussed. The behavior of the four Schiff bases in the heterogeneous chloroform-water mixture was then explored through the establishment of their acidity (pK A ) and distribution (Log K d ) constants in 1 M chloride medium and the acidity constants in aqueous medium (pK a ) were deduced. Results showed that an increase of the alkyl chain decreases the distribution of the ligands and increases their acidity. The extractive performance of the Schiff base amphiphiles were investigated towards Ni(II) from a chloride medium at 30°C. The analysis of extraction data revealed that the synthesized Schiff bases exhibit a better and faster extractability than many ligands reported in the literature.

The liquid-liquid extraction of copper(II) with bidentate mono-Schiff base extractants(HL), namely, N-salicylideneaniline (SA), N-(2-hydroxy-1-naphthalidene)aniline (HNA), N-salicylidene-1-naphthylamine (SN), and N-(2-hydroxy-1-naphthalidene)-1-naphthylamine (HNN), from a weakly acidic sulphate media into chloroform was studied in both the absence and the presence of acyclic polyether non-ionic surfactant (S). In the absence of the non-ionic surfactant, the extractability of copper(II) was 92.6% with SA, 89% with HNA, 81% with SN, and 80% with HNN. The estimated extraction constants, (log K ex ) of the four extractants revealed that the extraction efficiency increased in the order HNN, SN, HNA,SA. Besides, it was found that copper(II) was extracted as CuL 2 (HL) with SA and HNA, and as CuL 2 with SN and HNN. The extraction of copper(II) was significantly enhanced with HL into chloroform upon the addition of a non-ionic surfactant. An extractability of 100% was reached. The stoichiometry of the extracted complexes was CuL 2 S. The synergic extraction ability of extractants changed in the order SA.HNA.SN,HNN, whereas, the synergic effect fell in the order HNN.SN.HNA,SA.

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