Study on the Cloud Point Extraction of Copper(II) from an Aqueous Sulfate Medium with N,N′-Bis(salicylideneaminoethyl)amine Polydentate Schiff Base into a Nonionic Surfactant Phase

Abstract

A novel polydentate Schiff base extractant, N,N′-bis(salicylideneaminoethyl)amine (H2L), 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)−H2L, 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 (Na2SO4), 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:H2L). 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 Na2SO4; and (5) temperature of 65 °C.