Preconcentration of Cadmium with OP-10 Nonionic Surfactant Phases at the Cloud Point

Abstract

The micellar extraction of microcomponents with nonionic surfactant phases at the cloud point is one of the most promising analytical applications of organized surfactant media [1,2]. Extraction with nonionic surfactant phases is used for the preconcentration and separation of metal ions, organic toxicants, and biologically active compounds [3]. The advantages of micellar extraction are high absolute preconcentration coefficients for small sample volumes (50-100 mL); easy combination with chromatographic, spectroscopic, electrochemical, and other methods; improved performance characteristics; and a relatively low toxicity of the surfactants used [4][5][6]. In addition, the method is suitable for the effective and selective extraction of hydrophilic and hydrophobic compounds [7].The solubility of nonionic surfactants in water is due to the formation of hydrogen bonds between the oxygen atoms of the surfactant polyoxyethylene chain and water molecules [8]. When aqueous solutions of nonionic surfactants are heated above a specific temperature (cloud point, T c ), these bonds brake and phase separation occurs in the system. As a result, two phases are formed: the micellar phase of a nonionic surfactant composed of coarse hydrated micelles and the aqueous micellar solution of the same surfactant with the concentration close to critical micellation concentration. The micellar phase is used for the preconcentration of microcomponents.Aliphatic monocarboxylic acids and their derivatives are universal extractants; they were proposed for the preconcentration and separation of many metals, including cadmium, a typical anthropogenic environmental pollutant [9,10]. Carboxylic acids are characterized by a high extraction capacity due to their good solubility in organic solvents [10]. This property persists in the micellar solutions of nonionic surfactants [11]. The aim of this work was to study the extraction of cadmium with carboxylic acids into nonionic surfactant phases and to select conditions for its atomic absorption determination in natural and waste waters using micellar-extraction preconcentration. EXPERIMENTAL Reagents and apparatus.Polyoxyethylated alkylphenol OP-10 (Fine Organic Synthesis Plant, IvanoFrankovsk) with the average molecular weight of 647 g/mol, concentration of organic substance >99%, and the average degree of oxyethylation n = 10-12 [12] was used. OP-10 was selected, because it forms a compact and highly viscous nonionic surfactant phase upon heating and the phase formation proceeds more rapidly than that for other nonionic surfactants. OP-10 solutions were prepared by dissolving its portions in distilled water. C n H 2 n + 1 -C 6 H 4 -O-(C 2 H 4 O) m -H ( m = 10-12, n = 8-10).Fatty monocarboxylic acids of the general formula C n H 2 n + 1 COOH of analytical and reagent grade (for liquid and solid acids, respectively) were used. Solid acids were additionally purified by recrystallization from water-ethanol mixtures. Working solutions of acids were prepared by dissolving acid portions in aqueous solut...

Experimental Study on Migration and Intrusion Characteristics of Pulverized Coal in Propped Fractures

“…Due to the small width of the outlet end, a large amount of pulverized coal accumulates at the outlet end. The hydrophobic group of the nonionic surfactant (TX-100) [39] is adsorbed on the surface of the pulverized coal, and the hydrophilic group faces the liquid. These hydrophilic groups will accelerate wetting.…”

Study on Thermodynamics and Kinetics of Association Interactions between Malachite Green and OP-10 in Aqueous Solutions

“…[9][10][11][12][13][14][15]. OP-10 is nonionic surfactant, which contains hydroxyl and ether bond hydrophilic group, it is a sort of highly effective surfactant that has been used as leveling agent in wool dyeing, emulsifier in pesticide, medicine, rubber industry, and an important composition of metal water-based cleaning agent as well [16][17][18][19][20].…”

Micelle mediated extraction of cadmium from water and tobacco samples with glyoxal-bis(2-hydroxyanil) and determination by electrothermal atomic absorption spectrometry

“…Separation and preconcentration based on cloudpoint extraction (CPE) is becoming an important and practical application in the use of surfactants in analytical chemistry [5,6] because it does not require toxic organic solvents as used in SE. Many cloud point extraction procedures for cadmium determination have been developed, involving different kinds of analytical techniques and several chelating agents such as 1-(2-thiazolylazo)-2-naphthol (TAN) [7], dithizone (Dz) [8,9], O,O-diethyldithiophosphate (DDTP) [10][11][12][13][14][15], iodide [16], ammonium pyrrolidinedithiocarbamate (APDC) [17], 2-(5-brom-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP) [18], 1-(2-pyridylazo)-2-naphthol (PAN) [19], diethyldithiocarbamate (DDTC) [20], 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone [21], 8-hydroxyquinoline [22], capric acid/ n-octylamine [23], 2-(2-thiazolylazo)-p-cresol (TAC) [24], and 2-[2 0 -(6-methyl-benzothiazolylazo)]-4-bromophenol (Me-BTABr) [4] have been used to determine and preconcentrate traces of cadmium from various samples. Most Cd-chelating ligands were of thiol-type, in accord with the theory of Hard and Soft Acids and Bases (HSAB).…”