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

Abstract

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.

Dispersive Liquid-Liquid Semi-Microextraction of Сu(II) with 6,7-dihydroxy-2,4-diphenylbenzopyrylium Chloride for its Spectrophotometric Determination

“…A 0.1-0.3 g of CRM sample was transferred to a platinum crucible and 2 g of potassium persulfate was added and melted at 600 °C in a muffle for 25-30 min. After that, the melt was cooled and dissolved in water and diluted to 100 cm 3 . The obtained solutions were used for analysis by the proposed method.…”

“…Many various techniques for copper(II) preconcentration have been proposed. For example, cloud point extraction, [2][3][4] solid-phase extraction, [5][6][7] liquid extraction [8][9][10] etc., while most often copper(II) is pre-bound into ion pairs or complexes (chelates in particular) using reagents such as sodium diethyldithiocarbamate, [11][12][13] 1-(2-pyridylazo)-2-naphthol, 4,14 and dimethyl-1,10-phenanthroline (neocuproine). 15,16 It is important to note that interest in the development and modernization of various cloud point extraction and liquid extraction techniques does not disappear even today.…”

“…On the one hand, the use of semi-microtechniques notably reduces the environmental load and does not require special equipment like microextraction and is not fraught with errors related to dosing microliter volumes. On the other hand, the proposed DLLsME-UV/Vis procedure for copper(II) determination does not need extra time-consuming steps like, for example, heating and cooling of solution, 3 so the method is quite rapid. The 6,7-dihydroxy-2,4-diphenylbenzopyrylium chloride (DHDPhB) was chosen as the chelating ligand whose synthesis, physio-chemical, spectroscopic, and complexing properties were described in detail in our previous works.…”

“…* Concentration is given in μg/g for rocks samples and in μg/dm3 for tap water sample. ** The experimental t-values were calculated according to equation μ = x average ± tS/n ½ ; The critical t-value for five replicate measurements at a confidence level of 0.95 was 2.78.…”

Cloud Point‐Dispersive Liquid‐Liquid Microextraction for Extraction of Organic Acids from Biological Samples

“…When the sample solution contains analytes and surfactant heated to a temperature known as the cloud point temperature, phase separation has occurred and analytes extract to the surfactant-rich phase. Being time-consuming is the main disadvantage of CPE [21][22][23].…”