Values Of Extraction Constants Research Articles

Comparative study on extraction of copper(II) cations from highly saline media using 2-((phenylimino)methyl)phenol chelating mono-Schiff base /kerosene as novel extractant system

The present investigation reports a fundamental extraction- recovery studies of high amount of copper(II) cations from different concentrated saline aqueous solutions including sulphate, chloride, and mixed chloride/ sulphate media with 2-((phenylimino)methyl)phenol extractant (HPIMP) in kerosene at 25 °C. The acid-dissociation constant (Ka) and distribution constant (Kd) between kerosene and various saline aqueous solutions of (HPIMP) were determined. The influence of different parameters namely contact time, organic to aqueous phase (O/A) ratio, pH-value, extractant concentration, and temperature, as well as the effect of anions on the extraction recovery process has been studied. The experimental results revealed that the extraction ability of the (HPIMP) towards Cu(II) ions depends on the nature of inorganic salt. A maximum extraction efficiency of 99.76% was obtained from a 1 M chloride medium, which is significantly higher than those obtained from the sulphate medium (E(%) = 79.13%) or the mixed chloride/sulphate medium (E(%) = 81.75%). The trends in the values of extraction constants were explained in terms of acidity and distribution constants of (HPIMP). From the thermodynamic analysis it is inferred that the extraction process is endothermic and favorable at high temperatures, leading to stable, extractable Cu-HPIMP complexes.

Solvent extraction of copper from acidic chloride solutions with LIX 84

The extraction equilibria of Cu(II) from HCl and HCl-KCl solutions at different ionic strengths (0.05–0.50 mol/L) by LIX 84 in toluene is reported. Copper speciation in the aqueous solutions has been previously calculated using the Specific Interaction Theory (SIT) for the calculation of the activity coefficients. The effect of the concentrations of extractant, H+ and Cl− has been examined. Graphical and numerical treatments of the experimental extraction data indicate the extraction of a single complex of stoichiometry CuL2, HL being 2-hydroxy-5-nonylacetophenone oxime, the active component of LIX 84. EPR measurements of the organic extracts have confirmed the proposed stoichiometry. The copper extraction constant values at 0.05, 0.10, 0.25 and 0.50 mol/L HCl and at 0.50 mol/L (H+,K+)Cl− have been determined and successfully correlated with the ionic strength based on the previously developed aqueous phase chemical model. The value of the copper extraction constant at infinite dilution is also reported.

English

The mechanism of reactive extraction of pantothenic acid with tri-n-octylamine and di-(2-ethylhexyl) phosphoric acid was analysed for three solvents in the presence or absence of 1-octanol. In the absence of 1-octanol, the stoichiometric ratio between the solute and tri-n-octylamine was 1:1 for dichloromethane, 1:2 for butyl acetate, and 1:4 for n-heptane. In the presence of 1-octanol, the formation of aminic adducts was restricted, the stoichiometries for the interfacial reaction between the acid and tri-n-octylamine becoming 1:1 for dichloromethane and butyl acetate, 1:2 for n-heptane. A similar effect has been observed for extraction with di-(2-ethylhexyl) phosphoric acid, the structure of the interfacial compound being changed for n-heptane and butyl acetate from HAE 2 in the absence of 1-octanol to HAE by addition of this alcohol. The highest extraction constants were obtained when extractant associates were formed. However, when the extraction mechanism was the same, the increase in organic phase polarity influenced positively the value of extraction constant.

Synergistic Extraction of Cobalt(II) by Mixtures of Bis(2-Ethylhexyl)Phosphoric Acid and LIX 860

The extraction of Co(II) from 1.0 M KNO3 medium by mixtures of HDEHP (bis-2-ethylhexylphosphoric acid) and LIX 860 (5-dodecylsalicylaldoxime) dissolved in toluene has been studied. The effects of pH, metal, and extractant mixture concentrations on the extraction behavior have been examined. Synergistic extraction of the metal ion with the binary mixture of extractants has been found. Experimental results have been treated graphically and numerically by means of the Letagrop-Distr program and can be explained by assuming the extraction of two mixed complexes of general stoichiometry CoR2(HR)(HL) and CoR2(HR)(HL)3, HR being bis-2-ethylhexylphosphoric acid and HL standing for 5-dodecylsalicylaldoxime. The corresponding extraction constant values have also been determined.

Correlation of the Extraction Constant Values of Zn2+ and Cd2+ from Phosphoric Acid Media by Bis(2,4,4-trimethylpentyl)dithiophosphinic Acid Dissolved in Toluene

Values of the extraction constants of Zn2+ and Cd2+ from aqueous phosphoric acid solutions (0.36 to 7.31 mol⋅L−1) by Cyanex 301 in toluene, involving formation of the complexes ZnR2 and CdR2 with R being bis(2,4,4-trimethylpentyl)dithiophosphinate, have been correlated at T=298 K as a function of the ionic strength. For this purpose the activity coefficients of all of the aqueous species have been calculated taking into account both the protolytic equilibria of concentrated phosphoric acid and complexation reactions between the cations and the phosphoric acid species. Good correlations have been obtained for the extraction constant values with the ionic strength, provided the release of water molecules during the extraction processes is considered. Finally, extraction constant values are reported at infinite dilution.

Iron(III) Extraction from Phosphoric Acid Solutions by Cyanex 301

The extraction of Fe(III) from phosphoric acid solutions of different concentration ranging from 0.4 up to 7.3 M by Cyanex 301 in toluene is presented. The numerical treatment of the experimental data by means of the Letagrop program has allowed to propose the extraction of a single complex of stoichiometry FeR3, HR being bis(2, 4, 4-trimethylpentyl) dithiophosphinic acid, for which the stoichiometric extraction constant values at each phosphoric acid concentration have been obtained. Taking into account the model of concentrated phosphoric acid proposed by Elmore, the activity coefficients of the aqueous species have been calculated and the stoichiometric equilibrium constant at each phosphoric acid concentration has been successfully correlated with the ionic strength. The value of the extraction constant at infinite dilution is also given (log K 0 30 = 8.55 ± 0.02).

Liquid–liquid extraction of copper(II) with substituted salicylideneanilines from sulfate media

The liquid–liquid extraction of copper(II) with Schiff bases in chloroform from sulfate media is studied for pH and concentration of the extractant. Stoichiometry coefficients of the extracted species are determined by the slope analysis method. With salicylideneaniline, the copper(II) is extracted as a mixed chelate complex, CuL2HL. In the presence of substituent, the copper is extracted as simple chelates, CuL2. The trends in the values of extraction constants were explained in terms of the nature of the substituents.

Solvent extraction of americium by imidodiphosphates and diimidotriphosphates

Solvent extraction was described for determining of the americium content in the liquid samples. Arylesters of imidodiphosphoric, imidothiodiphosphoric, imidodithiodiphosphoric acids and tetraphenylimidodithiodiphosphine are used as representatives of bidentate organophosphoric extractants. From the group of tridentate agents, pentaphenyldiimidotriphosphate, was used. The extraction properties of tetraphenyl imidodiphosphates and their sulphur analogues for trivalent americium in 0.1 mol L−1 HNO3 into toluene also in the presence of tri-n-octylphosphine oxide (TOPO) were investigated. The dependences of equilibrium ratios of the americium on analytical or equilibrium concentration of chelating agents, pH, initial concentration of nitric acid and initial concentration of TOPO were studied. The structures of the complexes in the organic phase were determined and the values of extraction constants were calculated. The extracted species were AmA3, AmA3 (HA), the addition of TOPO induced synergistic extraction of AmA3 TOPO. The utilization of sulphur analogues was marginal.

SYNERGISTIC EXTRACTION OF COBALT(II) WITH MIXTURE OF ACYL-PYRAZOLON AND CROWN-ETHER IN STRONSIUM(II) ENVIRONMENT

Synergistic extraction of cobalt(II) with mixture of acyl-pyrazolon (HL) and crown-ether (E) in the Sr(NO3)2 environment has been studied. In this research, HPMBP (phenyl-1-methyl-3-benzoil-4-pyrazolon-5) was used, with three different kinds of crown-ether, i.e. (benzo-15-crown-5), DB18C6 (dibenzo-18-crown-6) and DB24C8 (dibenzo-24-crown-8), in chloroform. In the bulk environment of stronsium, a cobalt coextraction and stronsium occured with species ESrNO3+,Co(PMBP)3-, and E = B15C5, while Co(PMBP)2E and ESr,Co(PMBP3)2, with E = DB18C6. There was no coextraction when using crown-ether DB24C8, with the extracted species Co(PMBP)2E. Values of extraction constant presented in log Kex were -6.08 (B15C5), - 4.51, -12.55 (DB18C6), and - 4.57 (DB24C8), respectively. Keywords: synergistic, cobalt (II), strontium (II), coextraction.

Correlation of the extraction constant values of Cu(II) by 5-dodecylsalicylaldoxime from phosphoric acid media

The equilibrium constant values of copper(II) extraction from phosphoric acid media by LIX 622 (67.7% 5-dodecylsalicylaldoxime, Cognis Ireland) taking into account the formation in the organic phase of the complex CuL 2, HL being 5-dodecylsalicylaldoxime, at different ionic strengths have been calculated. Elmore's model has been considered for the speciation of the aqueous phase. A new approach for the calculation of the activity coefficient of H 2PO 4 − has also been proposed. The extraction equilibrium constant values obtained at the different ionic strengths have been successfully correlated considering the activity coefficients of the species in solution as well as the release of water molecules in the extraction process. The extraction constant value at infinite dilution of the complex CuL 2 is also reported.

RECOVERY OF p-HYDROXYBENZOIC ACID FROM WASTEWATERS BY REACTIVE EXTRACTION 1. EXTRACTION MECHANISM AND INFLUENCING FACTORS

The comparative study on reactive extraction of p-hydroxybenzoic acid with Amberlite LA-2 and D2EHPA in two solvents with different polarity (n-heptane and dichloromethane) indicated that the extractant type and solvent polarity control the extraction mechanism. Thus, the reactive extraction with Amberlite LA-2 occurs by means of the interfacial formation of an aminic adduct with three extractant molecules in low-polar solvent, or of an salt with one extractant molecule in higher polar solvent. Similarly, the extraction with D2EHPA is based on the formation of an acidic adduct with two extractant molecules in n-heptane, or of an salt with one extractant molecule in dichloromethane. The most efficient extraction has been reached for the combination Amberlite LA-2 - dichloromethane. The values of extraction constant depend on the formation of the interfacial hydrophobic adducts.

Fundamental Study on Solvent Sublation Using Salphen and Its Application for Separative Determination of Trace Ni(II), Co(II) and Cu(II) in Water Samples

A solvent sublation using salphen as a ligand was studied and applied for the determination of trace Ni(II), Co(II) and Cu(II) in water samples. The fundamental study was investigated by a solvent extraction process because the solvent sublation was done by extracting the floated analytes into an organic solvent from the aqueous solution. The salphen complexes of Ni(II), Co(II) and Cu(II) ions were formed in an alkaline solution of more than pH 8 and then they were extracted into m-xylene. It was known that the each metallic ion formed 1 : 1 complex with the salphen and the logarithmic values of extraction constants for the complexes were 3.3 5.1 as an average value. Based on the preliminary study, the procedure was fixed for the separation and concentration of the analytes in samples. Various conditions such as the pH of solutions, the influence of NaClO 4 , the bubbling rate and time of N 2 gas, and the type of organic solvent were optimized. The metal-salphen complexes could be extracted into m-xylene from the solution of more than pH 8, but the pH could be shifted to acidic solution of pH 6 by the addition of NaClO 4 . In addition, the solvent sublation efficiency of the analytes was increased by adding NaClO 4 . The recovery of 97-115% was obtained in the spiked samples in which given amounts of 0.3 mg/L Ni(II), 0.8 mg/L Co(II) and 0.04 mg/L Cu(II) were added.

Thermodynamic Modeling of Extraction Equilibria of Platinum and Palladium with Nonylthiourea from Hydrochloric Acid Media

Models of extraction equilibria of Pt(IV) and Pd(II) with Nonylthiourea (NTH) from HCl media have been studied. The conditional equilibrium constants and the stoichiometry of the extracted species of Pt(IV) with NTH at different ionic strengths obtained by numerical analysis using the LETAGROP‐DISTR program are reported. The dependence of the extraction constant values on the ionic strength has been analysed using the Specific Interaction Theory (SIT), from which the respective thermodynamic equilibrium constants of the extraction of Pt(IV) and Pd(II) with NTH have been determined. The thermodynamic equilibrium constants determined for Pt(IV) are log K 11 o = 5 ± 1 and log K 14 o = 14.6 ± 0.2, while for Pd(II) log K 11 o = 4.9 ± 0.1 and log K 12 o = 9.17 ± 0.08. The interaction coefficients, ϵ, for the pairs (H +, PtCl 6 2−) and (H +, PdCl 4 2−) have also been estimated to be 0.30 ± 0.08 and 0.41 ± 0.02, respectively.

Solvent extraction of Ga(III), Cd(II), Fe(III), Zn(II), Cu(II), and Pb(II) with ADOGEN 364 dissolved in kerosene from 1–4 mol dm −3 HCl media

Distribution equilibria of approximately 0.01 mol dm −3 Ga(III), Cd(II), Fe(III), Zn(II), 0.1 mmol dm −3 Cu(II) and Pb(II) from 1–4 mol dm −3 HCl media were studied using the commercial trialkylamine ADOGEN 364 (ADG) dissolved in kerosene as extractant. Self-association of this extractant in the organic phase was taken into account when analyzing the extraction reactions. Numerical analysis of the data with the LETAGROP-DISTR program allowed the evaluation of the equilibrium constants of the proposed equilibria. The dependence of the extraction constant values with ionic strength was analyzed using the specific interaction theory (SIT) treatment, from which the interaction coefficients of Ga(III), Cd(II), Fe(III), Zn(II), Cu(II), and Pb(II) with chloride anion were estimated. Data previously obtained for HCl and In(III) extraction were also analyzed in this form. Results obtained on the stoichiometry of extracted complexes are consistent with similar published work.

Extraction of pertechnetate with tetraphenylphosphonium in the presence of various acids, salts and hydroxides

Solvent extraction of pertechnetate anions from aqueous solutions of some mineral acids (HCl, HNO3, HClO4, H2SO4), (NaCl, NaNO3, NaClO4, K2CrO4, NaCO3), NaOH and NH4OH by tetraphenylphosphonium chloride in chloroform and nitrobenzene was studied. The results are presented in the form of the dependencies of extraction characteristics of TcO 4 − (distribution ratio, percentage of extraction) on the (C6H5)4PCl, H+ and competitive anion concentrations. The solvent extraction of sub-and super-stoichiometric ratio of TcO 4 − : (C6H5)4P+ was performed. The extraction constant values of ion pairs TcO 4 − −Cl−, TcO 4 − −NO 3 − , TcO 4 − −ClO 4 − and of individual anions TcO 4 − , Cl−, NO 3 − , ClO 4 − were calculated.

Extraction of cesium by the nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of dibenzo-18-crown-6

Extraction of cesium by the nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of dibenzo-18-crown-6 (DB18C6, L) was investigated. It was found, that besides hydrated cesium ion Csorg+ the complexes CsLorg+ and CsL2,org+ were extracted to nitrobenzene phase. No maximums on dependencies of the cesium distribution ratio (D) on the concentration of crown in the systemcL was found andD increased monotony withcL. Values of extraction constants and stability constants of extracted species in nitrobenzene have been determined.

Influence of the ionic strength on the formation and extraction of the strontium-cryptand 2.2.2-eosin ion-pair complex

Abstract A systematic study of the factors affecting the extraction of strontium, as an ion-pair formed between the positively charged cryptate of strontium with cryptand 2.2.2 and the eosinate anion, into chloroform has been carried out. The p K 1 and p K 2 values of the figand, the stability constant of the cryptate inclusion complex, as well as the partition coefficient and the extraction constant of the ion-pair, were measured as a function of the ionic strength of the solution. The p K a and K s values remained reasonably constant at ionic strength ⩽ 0.1 M. Nevertheless, the partition coefficient values, and consequently the extraction constant values, decrease as the ionic strength increases.

Extraction of hafnium into benzene with tetraphenyl imidodiphosphate

The distribution of hafnium(IV) was studied between aqueous solutions of perchloric, hydrochloric, or nitric acids (HX) and benzene solutions of tetraphenyl imidodiphosphate (HA). From perchloric and hydrochloric acids at concentrations cHX ⪬ 3 mol l-1 hafnium extracted as HfXA3 complex. With the two acids present at higher concentrations or with nitric acid at concentrations cHNO3 ≥ 1.5 mol l-1 the initial ion exchange mechanism turns into a solvation mechanism associated with the formation of HfX4(HA)y complexes (X = ClO4, Cl). The extraction constant values are given and the extracting agent is compared with other acid organophosphorus reagents.

Coloured liquid anion-exchangers

Of the several stable and coloured uninegative ions examined, trans-bis(dimethylglyoximato) dinitritocobaltate(III) ([Co(C 4H 7O 2) 2(NO 2) 2] -, termed goldenate ion, G -) can advantageously replace the erdmannate ion in the formation of a more photochemically stable coloured anion-exchanger derived from Aliquat-336 chloride. Quantitative spectrophotometric measurements of its displacement by chloride, bromide and perchlorate ions were made and are discussed together with literature data to examine the effect of parameters such as the nature of the cation and of the anion and change in the organic solvent on the relative and absolute values of extraction constants.

Extraction of Zn(II) and Cd(II) with anthranilic acid in the presence of nitrogen-containing organic bases

Zinc and cadmium anthranilates do not extract into non-polar solvents alone in the pH range 4.5–6.5. But their extraction is synergistically enhanced in presence of N bases, apparently by displacement of coordinated water. The synergistic effect varies with the bases in the order β-picoline > pyridine > quinoline. The values of extraction constants suggest that cadmium forms more stable complexes than zinc.