Computer modelling of the solvent extraction of iron by versatic acid from aluminium nitrate solutions

The development of a chemically based computer model of the extraction of ferric iron from concentrated aluminium nitrate solutions by Versatic 10 is outlined. The model uses previously determined equilibrium constants to calculate the distribution of iron in the various metal complexes present in the organic phase, together with empirical relationships for the pH changes occurring in the aqueous phase during extraction. A mean error of ±13% was found between computer predicted and experimentally determined organic phase iron concentrations for a four-stage counter-current extraction system. It is concluded that iron extraction by Versatic 10 is a technically feasible method of achieving aluminium nitrate with a sufficiently low iron content to enable the production of smelter grade alumina.     

Solvent extraction of zinc(II) and copper(II) with mixtures of LIX 34 and versatic 911 in kerosene

The solvent extraction of Zn(II) and Cu(II) with LIX 34 (HL) and mixtures of LIX 34 and Versatic 911 has been investigated. The compositions of the extracted complexes have been determined as ZnL₂ · HL and CuL₂. No synergism was found when mixtures of LIX 34 and Versatic 911 were used.     

The solvent extraction of lead from chloride solutions using di(2-ethylhexyl)phosphoric acid

Lead has been extracted from chloride solutions into kerosene containing excess di(2-ethylhexyl)phosphoric acid, using various concentrations of metal and extractant. Extraction proceeded readily, but the results indicated that 1.6 hydrogen ions were exchanged per atom of lead extracted, rather than 2.0 as would be expected for a divalent metal ion. Extraction was unaffected by metal concentration over the range studied (0.1–1.0 g l^?1), and the results were highly consistent. The unique log D vs. pH relation allowed simple collection of data for contact stage evaluation by rearrangement of the familiar solvent extraction equations and use of empirically derived constants. An S-shaped extraction isotherm resulted, which limits the ease with which aqueous lead concentrations may be reduced by extraction with di(2-ethylhexyl)phosphoric acid.     

The extraction of Zinc(II) from sulphate and chloride solutions with kelex 100 and versatic 911 in kerosene

Zinc(II) is extracted from sulphate or chloride solutions by Kelex 100 (HX) in kerosene, comparable extraction taking place under more acid conditions from chloride media. The addition of Versatic 911 (HA) leads to synergistic enhancement of extraction; equilibrium studies with the mixed extractants indicate that a mixed complex of the form ZnX₂ · (HA)₂ is extracted, and infra-red spectra suggest that Versatic is present as a solvating agent. The effect of chloride ion concentration on extraction was examined, and tracer studies showed that chloride takes no part in the constitution of the extracted zinc complex.     

Extraction equilibrium and extraction kinetics of nickel from aqueous ammonium nitrate solution with versatic 10 in n-hexane

The mechanism of extraction of nickel from an aqueous ammonia-ammonium nitrate mixture by an n-hexane solution of Versatic 10 was investigated from the viewpoint of extraction equilibrium and extraction kinetics. From the equilibrium study, it was found that nickel is extracted according to the following two extraction reactions which are in accordance with the loading ratio of nickel to Versatic 10:

$\text{Ni}{}^{\mathrm{2+}}\text{+ 3 H}{}_2\text{R}{}_{\mathrm{2org}}\text{?NiR}{}_2\text{·4 HR}{}_{\mathrm{org}}\text{+2 H}{}^{\mathrm{+}}{}_{\mathrm{aq}}$

in the range of lower loading ratio, and

$\text{2 Ni}{}^{\mathrm{2+}}{}_{\mathrm{aq}}\text{+ 4 H}{}_2\text{R}{}_{\mathrm{2org}}\text{?(NiR}{}_2\text{·2 HR)}{}_{\mathrm{2org}}\text{+4 H}{}^{\mathrm{+}}{}_{\mathrm{aq}}$

in the range of higher loading ratio. The equilibrium constants for each reaction were also determined. From the study of extraction kinetics, the extraction rate was found to be proportional to the total concentrations of nickel and Versatic 10 and inversely proportional to that of hydrogen ion. A reaction mechanism is proposed in order to give a reasonable explanation for the observed concentration dependence of each of the reactant species.     

A solvent extraction study of silver(I), palladium(II) and mercury(II) with 2-tert-dodecylthiopyridine

2-tert-Dodecylthiopyridine was synthesized from 2-chloropyridine and tert-dodecanethiol in order to examine its extraction properties for various metals. It was found to have good selectivity for the extraction of palladium(II) and mercury(II) over platinum(II) and -(IV) and base metals from chloride media; silver(I) was found to be almost completely extracted from nitric acid (0.01–5 mol/dm³ HNO₃). Palladium(II) and mercury(II) were completely extracted from hydrochloric acid over the range 0.01–2 and 0.01–0.5 mol/dm³ HCl, respectively. The rate of extraction of palladium(II) from hydrochloric acid was much faster than when using dialkylsulfide and triisobutylphosphine sulfide extractants. An aqueous mixture of thiourea and hydrochloric acid was found to be effective as stripping solution for palladium(II). The extent of stripping was dependent on the concentrations of either thiourea or hydrochloric acid.     

Complete separation of copper from cobalt by solvent extraction with triisooctylamine

The separation of copper from cobalt in chloride-containing aqueous solution using triisooctylamine has been investigated. It is shown that the complete separation of these two elements is possible by using different chloride levels in the extraction and stripping units of the apparatus.     

Thermodynamics and kinetics of lutetium extraction with HEH(EHP) in hydrochloric acid medium

Solvent extraction has been the most widely used technique for rare earths separation. In this study, thermodynamics and kinetics of lutetium extraction with HEH(EHP) in hydrochloric acid medium were investigated. The extraction mechanism and the relevant parameters were determined by experiment research which can guide the practical extraction process. The data indicated that chloride ion had no effect on lutetium extraction, the rate constant increased when stirring speed was enhanced. Effects of temperature, HEH(EHP) concentration, acidity, and chloride concentration were also studied. Thickness of the diffusion film was also calculated to be 4.66×10~(–3) cm at 150 r/min.     

Purification of zinc calcine leach solutions by exchange extraction with the zinc salt of “versatic” acid

Trivalent iron present in zinc sulphate solutions obtained by the leaching of zinc calcine with sulphuric acid can be removed by exchange extraction using a solution of the zinc salt of “Versatic” 10. Valuable metals, such as cobalt and copper, are not co-extracted and so may be recovered in the normal way.Contaminants, such as arsenic, in the solutions which may be harmful in the further course of the process can be effectively removed by coprecipitation with a a small amount of iron hydroxides.     

Metals extraction with carboxylic acids. I. Composition of complexes with nickel,cobalt(II) and iron(III)

A computer method has been developed to calculate the probable composition of complexes formed in the organic phase during the recovery of various metal ions from aqueous solutions by means of acidic extractants.The calculations suggest that with Versatic 10, nickel and cobalt form dimeric complexes. The number of covalently bound carboxylate groups depends on the loading of the extractant and may vary from 2 to $\text{1}\text{1}\text{2}$ to 1 per metal ion. The apparently “vacant” covalent bonds of the metal might carry hydroxyl groups. The number of solvating acid molecules per metal ion is 2 in the case of nickel and 0, 1 or 2 for cobalt.With octanoic acid cobalt probably forms mainly monomeric complexes. The number of covalently bound carboxylate groups is 2 per metal atom, even at high loadings. The number of solvating acid molecules varies with the degree of loading and may be 0, 1 or 2 per metal atom.The extraction of iron(III) with Versatic 10 has also been studied. Several possible species both dimeric and trimeric and containing both covalently bound carboxylate groups and solvating acid molecules and possibly also hydroxyl groups were indicated.     

Investigation of the extraction kinetics of cobalt and nickel and the optimization of operation parameters in a mixer-settler for the extraction of cobalt

The extraction kinetics of cobalt and nickel in a mixer-settler have been investigated. The extraction system comprised an aqueous phase of cobalt and nickel sulphate and an organic phase of 10% EHPNA (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) -kerosene. The experimental results showed that the extraction rates of both cobalt and nickel were high and the extraction rate of cobalt was generally higher than that of nickel.On the basis of research on the extraction kinetics of cobalt, an optimization computation was carried out with total cost as the objective function, and the optimum combination of extraction stage efficiency with the extraction operation parameters was determined. The optimization computation showed that it is best to adopt high input power and short mixer contact time for the extraction of cobalt. The computations also showed that very high extraction stage efficiency is not required for minimum costs.     

Study on the extraction mechanism and thermodynamics of Pb(II) with a o-phenylendiamine tetraacetic acid

The extraction mechanism and thermodynamics of Pb(II) with a novel o-phenylendiamine tetraacetic acid (H₄PDTA) were studied by high performance liquid chromatography with UV detector. The effects of extraction time, reciprocating oscillation frequency, Pb(II) concentration, H₄PDTA concentration and Pb(II) solution acidity on Pb(II) extraction were investigated. The results showed that the extraction ratio of Pb(II) increased with an increase of pH and H₄PEDTA concentration with a reciprocating oscillation frequency of 120 CPM (cycles per minute). The composition of the extraction complex was determined by slope methods and UV spectral analysis. The extraction mechanism of Pb(II) was proved to be a chelate extraction reaction and the values of thermodynamic function at 25°C were determined: \(\overline {K_{ex} } = 2.18 \times 10^3\), ΔG _r = –19.05 kJ mol^–1, ΔH _r = –9.965 kJ mol^–1 and ΔS _r = 30.47 J mol^–1 K^–1.     

Determination of organic phase complexes formed on extraction of iron(III) from aluminium nitrate solutions with versatic 10

The extraction of Fe(III) from concentrated aluminium nitrate solutions by Versatic 10 in Escaid 110 was studied, using an AKUFVE system for the determination of extraction isotherms at constant pH values. The extraction data were analysed initially by classical slope analysis but this was found to be inadequate due to the complexity of the organic phase speciation. A statistical technique was then used to evaluate the compositions of the organic phase complexes by finding the best fits to the extraction data. Equilibrium constants governing the extraction of these complexes were calculated. Independent measurements of the amount of Versatic acid bound in the organic iron complexes were made by quantitative infrared analysis of organic extracts. Agreement between the statistical and infrared results was good. Complexes of the general form (Fe(OH)_3? V_n·sHV)_x were found, where n varied from 1 to 2 and s from about 0.5 to 2.5, with both decreasing as the iron loading in the organic phase was increased. Values of 2 or 3 were generally found for x, indicating the predominance of dimers and trimers.     

Mixed solvent systems for the extraction and stripping of iron(III) from concentrated acid chloride solutions

The extraction of concentrated iron(III) from acid chloride solutions has been investigated with methyl isobutyl ketone (MIBK), tri-n-butyl phosphate (TBP), di(2-ethylhexyl) phosphoric acid (D2EHPA), and their mixtures in various proportions, at different acid concentrations. On comparing the extraction of iron(III) with mixed and individual extractant, it was found that both D2EHPA-MIBK and D2EHPA-TBP mixtures exhibit synergism, the latter having better extraction ability. The synergistic coefficients, at different initial acid concentrations for each mixed extractant system, were evaluated and compared. An increase in the concentration of MIBK and TBP in the mixed organic resulted in higher synergistic coefficient. The stripping of iron(III) from loaded D2EHPA was found to increase with the strip feed acid concentration, while from loaded organic mixtures, it initially increased and then decreased. Stripping of iron(III) from D2EHPA-MIBK loaded solvent is better then D2EHPA-TBP. The extracted iron species formed and the stripping reactions have been proposed. Ultraviolet visible spectra of the stripped organic phase support the result and the proposed mechanisms.     

Effect of manganese(II) and boric acid on the electrowinning of cobalt from acidic sulfate solutions

The effect of Mn(II) and boric acid on the electrowinning of cobalt from acidic sulfate electrolyte was investigated by electrochemical methods. The results indicated that the presence of Mn(II) or boric acid alone increased the current efficiency by 2 to 3 pct but that their combination had no additional effect. The preferred crystal orientation pattern changed from (110) (100) (101) to (100) (110) (101) in the presence of 0.1 to 10 g dm⁻³ Mn(II); an additional change, to (110) as the only preferred orientation, occurred at a very high concentration of Mn(II) (100 g dm⁻³). Boric acid had no effect on the crystal pattern of the cobalt deposits. In general, the presence of boric acid increased the brightness of all the deposits, irrespective of the presence of Mn(II) in the electrolyte, and had no effect on the deposit morphology. The cathode polarization behavior of the cobalt electrocrystallization was affected only marginally by the presence of Mn(II) in the electrolyte, but the presence of boric acid with or without Mn(II) had a significant effect. Boric acid was found to suppress the rate of electroreduction of cobalt on stainless steel by an order of magnitude, irrespective of the presence of Mn(II).     

Recommended nomenclature for solvent extraction (liquid-liquid distribution)

Recommendations are presented for nomenclature in solvent extraction chemistry and processes including definitions, preferred symbols, and comments on the acceptability or otherwise of certain terms and their use in particular situations. An attempt has been made to generalize the definitions to include any system of two immiscible liquid phases.     

硫脲浸出金精矿及石油亚砜矿浆萃取Au(Ⅰ)的研究

本文研究并选择了酸性硫脲浸出金精矿的最佳工艺条件,对石油亚砜从硫脲浸出矿浆中直接萃取Au(Ⅰ)的性能作了初步的探索。     

Mass transfer characteristics of cobalt and nickel in di(2-ethylhexyl)Phosphoric acid under steady-state extraction conditions

The mass-transfer characteristics of cobalt and nickel in di(2-ethylhexyl)phosphoric acid have been studied using a gradientless or steady-state stirred cell contactor. The effects of contacting conditions, stirrer Reynolds number, extractant concentration and organic phase loading were investigated. The results showed that under the conditions studied overall transfer rates could be considered diffusion or mass-transfer controlled. There was, however, evidence of an interfacial or chemical resistance as shown by the effect of contacting conditions on values of the overall mass-transfer coefficient, K_org. This was confirmed when experimental K_org values were compared with individual phase mass-transfer coefficient values predicted from correlations proposed in the literature by Lewis and by McManamey et al.     

The solvent extraction of zinc chloride with di-n-pentyl pentaphosphonate

The extraction of divalent zinc from aqueous solutions containing sodium chloride using di-n-pentyl pentaphosphonate [C₅H₁₁PO(OC₅H₁₁)₂] in kerosene has been investigated.Equilibrium data were in good agreement with equations of the form x/y = a + bx, where coefficients a and b have been mathematically demonstrated to have a physicochemical meaning: a is the reciprocal of the distribution coefficient at infinite dilution and b is the reciprocal of the maximum loading capacity of the organic solution.By adjusting the extraction isotherms to such a type of equation by the least-squares method, the effects of chloride concentration in the aqueous phase and di-n-pentyl pentaphosphonate (DPPP) concentration in the organic phase were determined, showing that the extraction of divalent zinc from chloride solutions by DPPP proceeds according to the solvating reaction:

$\text{Zn}{}^{\mathrm{2+}}\text{(a) + 2Cl}{}^{\mathrm{?}}\text{(a) + 2 DPPP(o) ? ZnCl}{}_2\text{· 2DPPP(o)}$

where (a) and (o) represent aqueous and organic phases respectively.The extraction equilibrium constant of such a reaction was also determined, resulting in K_EX = (30°C). Moreover, a mathematical model for the extraction reaction was established, allowing the calculation of equilibrium data as a function of the initial aqueous chloride concentration and organic DPPP concentration. Values of such data are given in comparison with experimental data and their perfect agreement demonstrates the validity of the theoretical model which will be used in a computer program for process flow-sheet simulation.     

The separation of selenium from tellurium in hydrochloric acid media by solvent extraction with tri-butyl phosphate

The separation of selenium from tellurium in hydrochloric acid media by solvent extraction with tri-butyl phosphate has been studied. Extensive laboratory experiments have been carried out at bench scale and pilot scale with different extraction apparatus. Results indicate that under the experimental conditions a high degree of separation between selenium and tellurium can be achieved by using 30 vol% TBP diluted with kerosene as the organic extractant. A process for the separation of selenium from tellurium by selective extraction has been proposed.