Thiosubstituted Organophosphorus Acids as Selective Extractants for Ag(I) from Acidic Thiourea Solutions

Abstract

This paper deals with the solvent extraction of silver from thiourea leaching Ag ore liquors as an alternative to the traditional process involving cyanide. The investigation of the extraction mechanism of silver from acidic thiourea solution had not been clearly established to date.

The extraction behavior of silver using di(2‐ethylhexyl)dithiophosphoric acid (D2EHDTPA) and di(2,4,4‐trimethylpentyl) thiophosphinic acid (CYANEX 302) was studied. The effect of various parameters such as concentrations of metal, mineral acid, thiourea, and extractant has been investigated. The extracted complexes have been identified through a slope method analysis as AgX(HX)₅ for CYANEX 302 and AgX for D2EHDTPA, where HX denotes the extractant. Moreover, complete stripping was ensured with a mixture of NH₄SCN and H₂SO₄. In addition we showed that a first step of extraction with D2EHPA or CYANEX 272 results in the preferential separation of Fe(III) from the Ag(I) leach solution.     

PHENOL RECOVERY WITH SLM USING “CYANEX 923”

The study of the phenol separation-concentration process with the hollow fiber supported liquid membrane technology has been performed. Mixtures of kerosene and CYANEX 923 were used as liquid membrane. The extractant CYANEX 923 is characterized by a high phenol selectivity and an extremely low solubility in the aqueous phase. The introduction of CYANEX 923 in the membrane composition decreases the extractant losses from the pores of the support.

The phenol separation and simultaneous concentration process has been checked. The influences of the initial concentration of phenol in the feed solution and sodium hydroxide in the stripping phase and the membrane composition on the separation rate have been investigated in a single-pass mode. The analysis of the membrane composition influence has been performed according to the steady-state mass transfer conservation equation and the associated boundary conditions, leading to the mass transfer parameters of the process     

Solvent extraction of titanium from nitrate medium using some organophosphorus extractants

The extraction of Ti(IV) from nitric acid has been carried out using some organophosphorus extractants in kerosene. The Ti(IV) extraction in the investigated systems is endothermic. Oxalic acid was effective for stripping Ti(IV). The maximum loading of Ti(IV) was found to be 6.13 × 10^?3, 6.175 × 10^?3 and 5.005 × 10^?3 M of Ti(IV) per mole extractant for CYANEX 925, 923 and 921, respectively, after five extraction stages. Kerosene is a more effective diluent for extraction of Ti(IV). FT-IR characterization and the separation of Ti(IV) are also discussed.     

Solvent extraction of lanthanides and yttrium from nitrate medium with CYANEX 925 in heptane

The extraction behavior of lanthanides and yttrium usinsg CYANEX 925 (mixture of branched chain alkylated phosphine oxides) in n‐heptane from nitrate medium has been studied. The effects of aqueous phase ionic strength, CYANEX 925 concentration in the organic phase, and temperature on Sm³⁺, Nd³⁺ and Y³⁺ extraction have been investigated. The extractability of the lanthanides and yttrium increases with increasing nitrate concentration, as well as with increasing CYANEX 925 concentration. An extraction mechanism is proposed based on slope analysis. Furthermore, the infra‐red spectra of CYANEX 925 saturated with lanthanides are employed to provide evidence of the composition of the complex. The relationship between the logarithm of the distribution ratio and lanthanide atomic number is also discussed which indicates that yttrium can be separated from light lanthanides. In addition separation of the light and heavy lanthanide groups is also possible using CYANEX 925. From the temperature dependence data, the thermodynamic parameters values (ΔH, ΔS and ΔG) are calculated. Copyright © 2007 Society of Chemical Industry     

Extraction and Separation of Zr(IV) and Hf(IV) from Nitrate Medium by Some CYANEX Extractants

Abstract

A solvent extraction study has been carried out to extract and separate zirconium and hafnium from nitrate medium by using some phosphine oxide extractants (CYANEX 921, CYANEX 923, and CYANEX 925) in kerosene. The influence of the different factors affecting the extraction process was studied in detail. Apparently the rate of extraction of Zr(IV) and Hf(IV) in CYANEX 921, CYANEX 923, and CYANEX 925 is reasonably fast. The extraction increases with increasing temperature, suggesting that the reaction is endothermic. The stripping percent of Zr(IV) and Hf(IV) by 0.5 M HNO₃ from the loaded organic phase after two stages reached 97.5% and 10.2%, respectively, which lead to good separation of the two metals. Under the optimum conditions, the extraction of zirconium was about 90, 87.6, and 91.6% and separation factors equal to 17, 21.4, and 40.7 were obtained for CYANEX 921, CYANEX 923, and CYANEX 925, respectively. The results obtained reveal that 2.0 M nitric acid is the optimum acid concentration for the separation of Zr(IV) and Hf(IV) and 0.4 M CYANEX 925 performs more efficient separation compared with other organophosphorus extractants.     

萃取法分离钒铬的竞争机制

采用伯胺萃取法分离钒铬,研究了不同Cr/V浓度比的钒铬溶液在一定初始pH值范围内的分离效果. 结果表明,伯胺萃取法分离钒铬具有很好的选择性,V(V)和Cr(IV)的萃取率均随溶液初始pH值降低而上升,相同加酸比[H+/V(Cr)摩尔比]下,钒铬混合溶液中V(V)萃取率高于其单金属溶液的萃取率,Cr(IV)萃取率低于其单金属溶液的萃取率,且萃取率随时间延长先上升后下降.     

Extraction of Palladium from Nitrate Medium by Emulsion Liquid Membrane Containing CYANEX 471X as Carrier

Extraction of Pd(II) from nitric acid solution with CYANEX 471X in chloroform was carried out using liquid–liquid extraction and emulsion liquid membrane (ELM) techniques. Extraction equilibrium was postulated using the slope analysis method. KSCN solution efficiently stripped Pd(II). In the ELM investigations, the effects of the different parameters affecting the membrane stability were studied. The prepared membrane was found to be selective for Pd(II) extraction in the presence of some interfering ions and its permeation reached 98%. The kinetics of Pd(II) permeation through the prepared membrane indicated that the rate of permeation depends on the carrier, Pd(II), and nitric acid concentration.     

Liquid-Liquid Extraction of Vanadium(V) and Niobium(V) with Tris(2-ethylhexyl)phosphate: Mutual Separation of Vanadium(V), Niobium(V), and Tantalum(V), and Analysis of Steel Samples

Abstract

Tris(2-ethylhexyl)phosphate (TEHP) dissolved in toluene is used for selective extraction of vanadium(V) and niobium(V) from hydrochloric and hydrobromic acid solution. Vanadium is determined spectrophotometrically after backextraction from TEHP, whereas unstripped niobium is determined in the TEHP phase with thiocyanate. The probable extractable species is VOCl₃·2TEHP or NbOCl₃·2TEHP/NbOBr₃·2TEHP. The method permits mutual separation of vanadium(V), niobium(V), and tantalum(V), and provides analysis of vanadium and niobium in alloys with a high degree of accuracy and precision.     

Extraction of Non-Ferrous Metals and Iron with Systems based on Bis(2,4,4-Trimethylpentyl)Dithiophosphinic Acid (CYANEX 301), A Review

Extraction is widely used in the hydrometallurgy of nonferrous metals. In addition to such well-known extractants as oxygen-containing organophosphorus or monocarboxylic acids, thio-substituted organophosphorus acids in particular, the commercially available extractant CYANEX 301, the active component of which is bis(2,4,4-trimethylpentyl)dithiophosphinic acid (HR), is of interest. This extractant is a sulfur-containing analogue of CYANEX 272 (bis(2,4,4-trimethylpentyl) phosphinic acid). In this review, the state of CYANEX 301 in various solvents in the absence and presence of electron-donor additives, the chemistry of the extraction processes of non-ferrous metals in the HR systems, the compositions of the extracted compounds, stability of the extractant in aggressive media, technological developments, and prospects for using CYANEX 301 in hydrometallurgy of non-ferrous metals are discussed.     

Kinetics and mechanism of extraction of Cu(II) by CYANEX 302 from nitrate medium and oxidative stripping of Cu(I) using Lewis cell technique

The extraction of Cu(II) from nitrate medium using CYANEX 302 (bis(2,4,4-trimethylpentyl) monothiophosphinic acid) in kerosene under equilibrium conditions showed that copper is first extracted as Cu²⁺ followed by reduction of CuA₂ (HA)₂ to Cu⁺ while the CYANEX 302 extractant is correspondingly oxidized. The stripping of Cu(II) from loaded organic solutions by using different stripping agents showed that effective stripping is obtained upon using high concentration of nitric acid which oxidizes the extracted Cu(I) to Cu(II).     

Adsorption of Ni(II) and Co(II) Using Microballoons Containing Mg-Silicate and CYANEX923 Prepared by the Emulsion Liquid Membrane System

Abstract

The Mg-silicate microballoons containing CYANEX923 were prepared by W/O/W emulsion. The diameter of obtained micro-sphere particles was ～10 µm and shell thickness was 2 µm. The adsorption of Co(II) and Ni(II) from aqueous solutions using prepared micro-sphere particles was investigated. Experiments were carried out as a function of solute concentration and temperature (25–60°C). Several kinetic models were used to test the experimental rate data and to examine the controlling mechanism of the adsorption process. Equilibrium adsorption data were analyzed using Langmuir isotherm model. The results indicated that prepared micro-sphere particles can be used as an efficient adsorbent for the removal of Ni(II) and Co(II) from aqueous solution.     

Separation of vanadium and tungsten in roasting-acid leaching solutions of the spent selective catalytic reducing denitration catalyst by co-extraction using hydroxyoxime extractant-quaternary ammonium salt extractant LIX984–N263 extractant

This study presents a synergistic extraction and recovery of vanadium and tungsten by mixed extractants (LIX984 and N263) from an acid leaching solution which was obtained from spent denitrification catalysts by chlorination heat treatment and acid leaching. Through thrice counter-flow extraction, 99.5% V and 99.7% W were extracted, while 3.0% Fe, 2.9% Ti, 2.1% P, and 3.3% Mg were co-extracted at a LIX984:N263 volume content of 22.0%, the phase ratio of 2.5 and the mother liquor's pH of 2.5. Then, at 0.80 mol/l NaOH and a phase ratio of 1, 99.9% tungsten and 99.1% vanadium were stripped from the organic phase to the aqueous phase. Subsequently, the aqueous phase's tungsten of 99.3% and vanadium of 98.1% were separated as calcium tungstate and ammonium metavanadate, respectively. In contrast, the residual solutions containing tungsten and vanadium can be returned to the following purification separation process to recover the valuable metals from the solution. Roasting converts the precipitated calcium tungstate and ammonium metavanadate to V₂O₅ and WO₃ products. In addition, the thermodynamic analysis found the separation and recovery of tungsten and vanadium from the acid leach solution with LIX984:N263 to be an exothermic process. This method can be effectively extended for the separation of vanadium and tungsten from spent denitrification catalysts by the proposed process and validates the conclusion that metals with similar properties can be extracted using a mixture of extractants.     

Comparison of Two Solvent Extraction Systems for the Separation of V(V) and Cr(VI) from an Industrial Leaching Solution

Two solvent extraction systems for V (V) and Cr (VI) separation in leaching solution were investigated in order to select the suitable separation method for the disposing of chromium-bearing vanadium slag. The best/suitable system was determined by extraction yield (E_V，%) and the separation factor of V(V) and Cr(VI) (β_V/Cr). On the condition of 1:1 molar ratio of H⁺ to vanadium (V), the E_V values were 99.8% and 95.1%, while the β_V/Cr values were 546.58 and 29.53 using the two different systems, respectively. The extraction reactions for system 1 were determined by the slope method, and the chemical equilibrium constants were obtained.     

钒铬还原渣酸浸液中钒铬初步分离工艺

钒铬还原渣是钠化提钒过程的典型危险固体废弃物,其资源化利用需求迫切。中国科学院过程工程研究所提出钒铬还原渣硫酸酸解-钒铬初步分离-铬/钒/铁络合深度分离技术路线,并在攀钢集团建成万吨级示范工程。本文重点考察钒铬还原渣酸解液中钒铬初步分离原理及工艺,研究了H₂O₂和Na₂S₂O₈两种氧化剂对沉钒效果的影响,并通过实验确定了最佳工艺条件。结果表明：以H₂O₂为氧化剂时,H₂O₂与钒摩尔比为0.75、氧化温度为60℃、初始溶液pH为2.0、氧化时间为60min、水解温度为95℃、水解时间为2.5h的条件下可得到84.2%的沉钒率;以Na₂S₂O₈为氧化剂时,Na₂S₂O₈与钒摩尔比为0.65、氧化温度为90℃、氧化时间为45min、沉钒初始溶液pH为2.5、沉钒温度为90℃、沉钒时间为2.5h的条件下可获得93.1%的沉钒率。过硫酸钠氧化过程温和,沉钒率高,铬损失小,更适合工业推广应用。采用SEM获得了沉淀产物的微观形貌,煅烧后得到V₂O₅产品,采用XRF获得了产品组成,通过X射线衍射确定得到的V₂O₅产品为正交晶型。     

黏土钒矿直接常压活化酸浸提钒热力学分析

目前黏土钒矿直接酸浸的试验以及基础性研究较少,为了进一步推动此类问题的研究进展,本项研究采用试验结合热力学计算的方法,通过试验得到了最佳浸出剂结果,运用热力学计算诠释了活化浸出钒过程的热力学行为以及其机理,同时进一步分析了不同硫元素的总量对酸浸液中各组分的影响,为从酸浸液中提钒工艺进行了溶液化学分析。结果表明：二氧化锰有能力将低价钒氧化至高价钒,从而提升钒的浸出率,升高温度对浸出率的提高以及二氧化锰的氧化均会造成不利影响,但是会抑制杂质的浸出,对杂质分离起到积极影响。硫酸的用量一方面会影响浸出过程的pH,同时会影响酸浸液中各组分的含量,低硫的酸浸体系与高硫体系中钒的离子形态存在差异。低硫体系中铁杂质的溶解度会小于高硫体系,有利于提钒过程中杂质的分离。通过分析浸出过程中溶液组分的变化,可以为后续提钒工序提供理论依据。     

应用[Omim][BF_4]为萃取剂分离钒铬渣酸浸液中钒/铬的研究

离子液体是一种新型绿色溶剂,在重金属离子萃取分离方面较传统的有机物质有显著的优势,但其成本昂贵是制约其作为溶剂应用的重要瓶颈,将其作为重要萃取剂是其扩大应用的一种有效途径。研究了1-辛基-3-甲基咪唑四氟硼酸盐离子液体([Omim][BF_4])萃取分离V(Ⅴ)、Cr(Ⅲ)的影响因素,包括相比(O/A)、时间、温度及金属离子初始质量浓度。结果表明,[Omim][BF_4]对于钒铬渣酸浸液中的V(Ⅴ)具有较好的萃取选择性,而对于Cr(Ⅲ)的萃取能力较弱,可以用于钒铬分离,为钒铬渣的绿色资源化利用开辟了新的途径。     

Three-liquid-phase extraction and separation of V(V) and Cr(VI) from acidic leach solutions of high-chromium vanadium–titanium magnetite

A new method by liquid–liquid–liquid three phase system, consisting of acidified primary amine N1923(abbreviated as A-N1923), poly(ethylene glycol)(PEG) and (NH_4)_2SO_4 aqueous solution, was suggested for the separation and simultaneous extraction of V(V) and Cr(VI) from the acidic leach solutions of highchromium vanadium–titanium magnetite. Experimental results indicated that V(V) and Cr(VI) could be selectively enriched into the A-N1923 organic top phase and PEG-rich middle phase, respectively, while Al(III)and other co-existing impurity ions, such as Si(IV), Fe(III), Ti(IV), Mg(II) and Ca(II) in acidic leach solutions,could be enriched in the(NH_4)_2SO_4 bottom aqueous phase. During the process for extraction and separation of V(V) and Cr(VI), almost all of impurity ions could be removed. The separation factors between V(V) and Cr(VI) could reach 630 and 908, respectively in the organic top phase and PEG middle phase, and yields of recovered V(V) and Cr(VI) in the top phase and middle phase respectively were all above 90%.Various effects including aqueous p H, A-N1923 concentration, PEG added amount and(NH_4)_2SO_4 concentration on three-phase partitioning of V(V) and Cr(VI) were discussed. It was found that the partition of Cr(VI) into the PEG-rich middle phase was driven by hydrophobic interaction, while extraction of V(V) by A-N1923 resulted of anion exchange between NO_3~- and H_2V_(10)O_(28)~(-4). Stripping of V(V) and Cr(VI) from the top organic phase and the middle PEG-rich phase were achieved by mixing respectively with NaNO_3 aqueous solutions and Na OH-((NH_4)_2SO_4 solutions. The present work highlights a new approach for the extraction and purification of V and Cr from the complex multi-metal co-existing acidic leach solutions of high-chromium vanadium–titanium magnetite.     

Separation and recovery of vanadium from leached solution of spent residuehydrodesulfurization (RHDS) catalyst using solvent extraction

Leached solution, generated by oxalic acid washing of spent residue hydrodesulfurization (RHDS) catalyst, was used for separation and recovery of vanadium. First of all, solvent extraction, using mixture of 20% (v/v) Alamine-336 and 5% (v/v) tri-butyl phosphate (TBP) as a phase modifier, was conducted to extract molybdenum completely at pH 0.50. Then molybdenum-free solution was used for vanadium extraction at pH 1.25 with 20% Alamine-336 and 5% TBP. Stripping of vanadium from loaded organic solution was performed with 1.5 M H₂SO₄ at O/A phase ratio of 5:1 where more than 99% of vanadium was stripped in two stages. The stripped vanadium solution was further processed by precipitating with ammonium hydroxide to recover ammonium-meta-vanadate which was calcined to obtain vanadium pentoxide. Finally a conceptual process was established for recovery of high purity vanadium pentoxide from oxalic acid leached solution of spent residue hydrodesulfurization (RHDS) catalyst.     

SOLVENT EXTRACTION OF POLYVANADATES FROM SULPHATE SOLUTIONS BY PRIMENE 81R. ITS APPLICATION TO THE RECOVERY OF VANADIUM FROM SPENT SULPHURIC ACID CATALYSTS LEACHING SOLUTIONS

Recovery of vanadium from a spent catlaysts leaching process has been studied using primary amine PRIMENE 81R, resulting in an industrial multistage process for the treatment of these effluents. An extraction mechanism for V(V) is proposed for this amine in acidic media, verifying the influence of pH on the process. Adequate ranges for the variables: O/A ratio, organic phase composition, pH, stirring speed and phase separation speed were fixed and simulated in industrial conditions. Vanadium is finally recovered by means of precipitation as ammonium metavanadate and later calcination to obtain vanadium pentoxide of commercial grade.