Kinetics, thermodynamic and chromatographic behaviour of the uranyl ions sorption from aqueous thiocyanate media onto polyurethane foams

The retention profile of uranyl ions from aqueous thiocyanate media by polyether-type based polyurethane foams (PUFs) has been studied to gain more information regarding the mechanism of extraction. The effect of pH, shaking time, surfactant type, extraction media, temperature and analyte concentration on the retention of uranyl ions onto PUFs has been studied. It has been found that, the sorption of uranyl ions involved in the formation of a ternary complex ion associate of uranyl ion, thiocyanate and PUFs is highly dependent on these parameters. The kinetics and thermodynamics of the uranyl ions sorption have been studied in more detail. The dependency of the extraction on the parameters can be explained via a “solvent extraction,” mechanism. However, owing to the complex nature of the PUFs a dual-mode sorption mechanism involving both absorptions related to “solvent extraction” and an added component for “surface adsorption” may be operated simultaneously. Attempts for quantitative retention and recovery of the uranyl ions in tap and industrial waste water samples by the proposed PUFs columns has been carried out and satisfactory results have been obtained. The cellular structure of the PUF sorbent offer unique advantages over a conventional bulk type sorbents in rapid, versatile effective separation and/or preconcentration of uranyl ions.     

Extraction of uranium(VI) and thorium(IV) from nitric acid solution by N-alkylcaprolactam

Extraction of uranium(VI), thorium(IV) from nitric acid has been studied with N-octylcaprolactam and N-(2-ethyl)hexylcaprolactam. Distribution coefficients of U(VI), Th(IV) and HNO₃ as a function of aqueous NHO₃ concentration, extractant concentration and temperature have been studied. The compositions of extracted species, thermodynamic parameters of extraction have been evaluated. Third phase formation in extraction of U(VI) has been studied. Back extraction behavior of U(VI) and Th(IV) from the organic phase has also been tested. The results obtained are compared with those obtained by using TBP under the same experimental conditions.     

Substoichiometric extraction of gold(III). Determination of the extraction constant of gold dichloride diethyldithiocarbamate

The extraction constant of gold dichloride diethyldithiocarbamate has been determined (log K = 68.2 ± 0.2) by studying the competition from palladium in the substoichiometric extraction of gold with copper diethyldithiocarbamate in chloroform. Experimental conditions that allowed the equilibrium to be reached for any palladium concentration were chosen so that the influence of the palladium concentration on the extraction kinetics has also been studied. A program for the computation of any stability constant from extraction data for mixtures of three cations has been written.     

Rhenium(VII) extraction with Versatic hydrazides and <Emphasis Type="Italic">N',N'</Emphasis>-Dialkylhydrazides

Rhenium(VII) and molybdenum(VI) extraction with kerosene solutions of α-branched tertiary carboxylic Versatic acids derivatives containing hydrazide C(O)NHNH2 and C(O)NHNCH₃)₂ fragments instead of carboxyl group has been studied. Optimal extraction conditions have been determined depending on H₂SO₄, HCl, and extractant concentrations and composition of extracted complexes has been established. The mechanism of extraction and back extraction of perrhenate ion with ammonia solutions has been suggested.     

Extraction studies of the group IB,IIB, and IIIA–VA elements using 1-(2-pyridylazo)-2-naphthol as chelating reagent

The extraction of PAN chelates of the group IB, IIB and IIIA–VA elements from aqueous solutions of pH 1–10 into chloroform has been studied radiochemically. Re-extraction studies have been made to strip the metal ions from the organic phase into aqueous solutions of KCN, HClO₄ and buffer solutions. The effects of certain masking agents on the extraction of these elements have also been studied. The extraction curves indicate the possibilities of devising group chemical separation procedures for use in activation analysis.     

Extraction of gold(III) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-yl-methyl)-pentan-3-ol from hydrochloric acid solutions

Extraction of gold(III) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)-pentan-3-ol from 3 M hydrochloric acid solutions (with chloroform as a diluent) has been studied. Optimal extraction conditions have been found. The reagent has been shown to extract efficiently metal ion from solutions containing 3 M hydrochloric acid due to formation of coordination bond between gold(III) and the N4 atom of the triazole ring. The coordination mechanism of gold(III) extraction has been proposed on the basis of the data obtained. Concentration constants of extraction have been calculated, and the thermodynamic parameters of extraction have been determined.     

Solvent extraction of Zn/II/ with 1,2,3-benzotriazole into n-hepatanol

A method based on solvent extraction has been developed for the radiochemical separation of Zn/II/ from other elements employing 1,2,3-benzotriazole as a complexing agent and n-heptanol as an extractant. Optimum conditions for the extraction have been established. The effect of various anions and cations on the extraction coefficient value of Zn/II/ has been studied. The stoichiometry of the metal to reagent determined by the method of substoichiometric extraction and slope-ratio method was found to be 12.     

Enhancing Metal Separations by Liquid–Liquid Extraction Using Polar Solvents

The less polar phase of liquid–liquid extraction systems has been studied extensively for improving metal separations; however, the role of the more polar phase has been overlooked for far too long. Herein, we investigate the extraction of metals from a variety of polar solvents and demonstrate that, the influence of polar solvents on metal extraction is so significant that extraction of many metals can be largely tuned, and the metal separations can be significantly enhanced by selecting suitable polar solvents. Furthermore, a mechanism on how the polar solvents affect metal extraction is proposed based on comprehensive characterizations. The method of using suitable polar solvents in liquid–liquid extraction paves a new and versatile way to enhance metal separations.     

Extraction of group IB,IIB and III-VA elements with 1-phenyl-3-methyl-4-trifluoroacetyl-pyrazolone-5

The extraction of group IB, IIB and IIA-VA elements with 1-phenyl-3-methyl-4-trifluoroacetyl-pyrazolone-5 in chloroform has been investigated as a function of pH. The stripping of metal ions into solutions of KCN, HClO₄ and appropriate pH buffers has been studied. The masking effects of cyanide, citrate, iodide, thiosulphate and thiourea on the extraction have been examined. Selective group and individual separations have been proposed on the basis of pH control, masking effects and back-extraction.     

Studies on extraction of copper(II) with 1-phenyl-3-methyl-4-acyl-5-pyrazolone

The extraction of Cu(II) with 1-phenyl-3-methyl-4-acyl-5-pyrazolone (HA), in different organic solvents has been studied. The extraction mechanism of Cu(II) and the composition of the extracted species has been determined. Cu(II) was extracted as CuA₂, or in the presence of TOPO, as CuA₂TOPO. The extraction constants do not change regularly with increasing the length of acyl chain in the 1-phenyl-3-methyl-4-acyl-5-pyrazolone derivatives. The effect of the temperature on the extraction of Cu(II) has also been investigated.     

Extraction of uranium(VI) with bis(octylsulfinyl)methane

The liquid-liquid extraction of uranium(VI) from aqueous nitric acid with bis(octylsulfinyl)methane (BOSM) has been studied over a wide range of conditions. The extracted species appear to be UO₂(NO₃)₂·2BOSM. It was found that the extraction increased with increasing nitric acid concentration up to 8.5 mol/l and then descreased. Extraction also increased with increasing extractant concentration. The influence of temperature and salting-out agent concentration on the extraction equilibrium has also been investigated, and the enthalpy of the extraction reaction was estimated.     

Solvent extraction of Ru(III) with 2-mercaptobenzimidazole into n-butanol

A new and rapid method has been developed for the quantitative extraction of Ru(III) with 2-mercaptobenzimidazole into n-butanol. The extraction coefficient of Ru(III) between n-butanol and an ethanolic solution of 1% 2-mercaptobenzimidazole showed a maximum value ofE=161 at a pH of 2.0. The effect of various other parameters on the extraction coefficient value of Ru(III) such as solvent effect, anions, cations, etc. have also been studied. The stoichiometry of metal to reagent has also been determined by the method of substoichiometric extraction and by the slope ratio method and was found to be 1∶3. Decontamination factor for various elements in the substoichiometric extraction of Ru(III) were also evaluated.     

Investigation on phenolic compounds stability during microwave-assisted extraction

The stability of 22 phenolic compounds of different families (benzoic acids, benzoic aldehydes, cinnamic acids, catechins, coumarins, stilbens and flavonols) has been studied under conditions of microwave-assisted extraction. The influence on the stability affected by the working temperature between 50 and 175 degrees C has been evaluated, and it has been concluded that all the compounds studied are stable up to 100 degrees C, whereas at 125 degrees C there is significant degradation of epicatechin, resveratrol and myricetin. Conclusions have been drawn on the relationship between the chemical structure and the stability of the compounds; it has been found that those that have a greater number of hydroxyl-type substituents are more easily degraded under the extraction conditions.     

The use of14C,59Fe and65Ni radionuclides for the study of solvent effects on the extraction equilibria with n-caprylic acid

The distribution of n-caprylic acid between an aqueous sodium sulphate solution and several organic diluents of various properties has been investigated, using¹⁴C-labelled n-caprylic acid. The distribution coefficients of the monomeric capyrlic acid and its dimerization constants in the organic phase were determined. The extraction of Fe(III) and Ni(II) with n-caprylic acid solutions in various diluents was studied using the AKUFVE solvent extraction equipment. The composition of the extracted compound of Fe(III) has been determined and the extraction constants for all the studied systems have been calculated. For the extraction of Ni(II) the constants of the extraction of nickel caprylate monomers and its dimerization constants in the organic phase have been calculated.     

Study on the synergic extraction of uranium(VI) with petroleum sulfoxides (PSO) and tri-n-butyl phosphate (TBP) mixture

The synergic extraction of uranium(VI) from nitric acid solution with petroleum sulfoxides (PSO) and tri-n-butyl phosphate (TBP) mixture has been studied. It has been found that maximum synergic extraction effect occurs if the molar ratio of PSO to TBP is two to three. The composition of the complex of synergic extraction is UO₂(NO₃)₂·TBP·PSO. The formation constant of the complex isK _PT=8.19. The effect of extractant concentration, nitric acid concentration, salting-out agent concentration and temperature on the extraction equilibrium of uranium(VI) was also studied.     

Extraction of thorium from aqueous nitric acid solution by bis-2-(butoxyethyl ether) (DBC)

The solvent extraction of thorium(IV) (4.3·10^–4M) from nitric acid solution by bis-2-(butoxyethyl ether) (butex or DBC) has been studied. It has been investigated as a function of nitric acid, extractant and metal ion concentration. The effect of equilibration time, diverse ions and salting-out agent on the extraction has also been examined. Among anions, fluoride, phosphate, oxalate and perchlorate have reduced the extraction. Cations such as Na(I), K(I), Ca(II), Zn(II), Al(III), Ti(IV), Zr(IV) except Sr(II) and Pb(II) do not interfere in the extraction. The extraction is enhanced upto 97% in three stages at 6M HNO₃ having 2.94M NaNO₃ as salting-out agent. The extraction is found to be independent of thorium concentration in the range studied (4.3·10^–4–4.3·10^–2M). The temperature (18–45°C) has an adverse effect on the extraction. A 1% solution of ammonium bifluoride is found to be a good stripping solution and recovery of thorium is >98%.     

GC-NPD investigation of the recovery of organonitrogen and organophosphorus pesticides from apple samples: The effect of the extraction solvent

Summary A gas chromatographic method employing a capillary column and a selective nitrogen/phosphorus detector (NPD) has been developed for the determination of organophosphorus (OP) and organonitrogen (NP) pesticides in horticultural samples (apples). The separation of sixteen pesticides and the internal standard was performed in thirteen minutes. The analytical characteristics of the method, including linear response ranges, detection limits, and reproducibility, have been studied using a 11 mixture of ethyl acetate and xylene as extraction solvent. The possibility of mutual interference between pesticides has also been studied. A procedure for the quantitative extraction of the sixteen pesticides from apple samples has also been developed; for fifteen of the pesticides recoveries >85% were obtained after 90 minutes extraction. The effect of different solvents both on recovery and on the sensitivity of the subsequent chromatography were also investigated. It was found that the sensitivity required must be considered when the solvent for sample treatment is selected.     

Solvent extraction of Tl/I/ with 2-mercaptobenzothiazole into chloroform

The extraction of Tl/I/ with 2-mercaptobenzothiazole into chloroform has been studied. The effect of various parameters on the extraction coefficient value has been evaluated. The stoichiometry of the extracted species obtained from the substoichiometric extraction was found to be 11. This war further supported by the slope ratio method. Decontamination factors of a number of elements in the substoichiometric extraction of Tl/I/ were also obtained.     

Comparison of quantitative and substoichiometric determination of caesium from fission products with nitrobenzene solution of lithium dipicrylaminate

A method of determination of ¹³⁷Cs in a fission product by extraction with a nitrobenzene solution of lithium dipicrylaminate is described. The effect of pH and the amount of reagent on the efficiency of extraction of micro-amounts of caesium has been studied as well as the competing effect of alkali metal salts; the possibility of substoichiometric determination of caesium has been also investigated. Both procedures have been tested with an artificial mixture of fission products.     

Extraction of chlororuthenium(III) complexes by triazole derivatives from hydrochloric acid solutions

The extraction of ruthenium(III) by triazole derivatives from hydrochloric acid solutions has been studied. The extraction of ruthenium(III) is implemented by the ion-association mechanism. The composition of the extraction compound has been determined using electronic, ¹H NMR, ¹³C NMR, and IR spectroscopy and elemental analysis.