Organophosphorous Extractants Research Articles

The Sustainable Approach of Process Intensification in Biorefinery Through Reactive Extraction Coupled with Regeneration for Recovery of Protocatechuic Acid.

In the current scenario, where environmental degradation, global climate change, and the depletion of petroleum feedstock pose significant challenges, the chemical industry seeks sustainable alternatives for manufacturing chemicals, fuels, and bioplastics. Biorefining processes that integrate biomass conversion and microbial fermentation have emerged as preferred approaches to create value-added compounds. However, commercializing biorefinery products is hindered by dilute concentrations of final products and the demand for high purity goods. To address these challenges, effective separation and recovery procedures are essential to minimize costs and equipment size. This article proposes a biorefinery route for the production of protocatechuic acid (PCA) by focusing on in situ PCA separation and purification from fermentation broth. PCA is a significant phenolic molecule with numerous applications in the pharmaceutical sector for its anti-inflammatory, antiapoptotic, and antioxidant properties, as well as in the food, polymer, and other chemical industries. The chemical approach is predominantly used to produce PCA due to the cost-prohibitive nature of natural extraction techniques. Reactive extraction, a promising technique known for its enhanced extraction efficiency, is identified as a viable strategy for recovering carboxylic acids compared to conventional methods. The extraction of PCA has been explored using various solvents, including natural and conventional solvents, such as aminic and organophosphorous extractants, as well as the potential utilization of ionic liquids as green solvents. Additionally, back extraction techniques like temperature swing and diluent composition swing can be employed for reactive extraction product recovery, facilitating the regeneration of the extractant from the organic phase. By addressing the challenges associated with PCA production and usage, particularly through reactive extraction, this proposed biorefinery route aims to contribute to a more sustainable and environmentally friendly chemical industry. The incorporation of PCA in the biorefinery process allows for the utilization of this valuable compound with diverse industrial applications, thus providing an additional incentive for the development and optimization of efficient separation techniques.

Synergistic Extraction of Ga(III) from Chloride Solution by Mixture of Cyanex 272 and Alamine 336

Aming to select a suitable system for the synergistic solvent extraction of Ga(III), solvent extraction (SX) experiments were carried out by using acidic organo-phosphorous extractants, namely P204, P507 and Cyanex 272, and their mixtures with neutral extractants (TBP, N503) or amine extractants (Alamine 336). Among the studied mixtures, a remarkable synergistic effect for Ga(III) extraction was resulted by the combination of Cyanex 272 and Alamine 336 and the maximal synergistic enhancement coefficient reached 3.11. Compared to the single Cyanex 272, higher equilibrium pH values were observed when mixture of Cyanex 272 and Alamine 336 was employed. The extraction of hydrogen ions by Alamine 336 during the reaction was considered to be responsible for the synergistic extraction, and thus the the extraction of Ga(III) by Cyanex 272 was promoted. Finally, the synergistic extraction stoichiometry of mixture of Cyanex 272 and Alamine 336 for Ga(III) was projected by slope analysis. Ga(OH)A2 was resulted to be the composition of extracted complexes.

Increasing the circularity of the copper metallurgical industry: Recovery of Sb(III) and Bi(III) from hydrochloric solutions by integration of solvating organophosphorous extractants and selective precipitation

The lack of high-purity ores has made the copper industry exploit low-impurity ores containing As, Sb and Bi which can affect the final product quality due to the floating insoluble arsenates. This is usually solved by treating the electrorefining electrolyte in a polishing stage devoted to removing Sb and Bi using aminophosphonic resins. Once the resin is saturated, it is regenerated using 6 M HCl, and the eluate produced is treated with CaO(s) to precipitate both Sb and Bi. However, this stream is of interest due to the inclusion of both elements in the Critical Raw Material list from the European Union. Therefore, the linear management option must be substituted by a circular approach. This work aims to develop such approach by the selective separation and recovery of Sb and Bi from HCl stream polluted with As. The method presented was based on the use of using a solvating mixture of alkylphosphine oxides commercialized as Cyanex 923 dissolved in kerosene and 1-decanol (10 %) as phase modifier. The separation factors of Sb(III) and Bi(III) from As(V) were evaluated and optimized as function of both extractant concentration and the aqueous to organic phase ratio. Results showed that at the lowest Cyanex 923 concentration (0.15 mol/L) and working at an A/O ratio of 1/3, it could be possible to extract 39 % Bi and 78 % Sb with As co-extraction below 2.5 %. Both Sb and Bi were easily recovered (>90 %) using 8 M HNO3 as stripping agent. Following a treatment using NaOH/NaCl or NaOH, both elements could be recovered either as oxychlorides (SbOCl(s) and BiOCl(s)) or oxides (Sb2O3(s) and BisO3(s)).

Theoretical study on the extraction behaviors of MoO22+ with organophosphorous extractants

99Mo is the parent isotope of 99mTc, which is commonly used in nuclear medicine, so the studies on the extraction of 99Mo have been attracted extensive attention. There are some experimental investigations about the extraction of Mo(VI) using the organophosphorous extractants including O-donor Cyanex 272 (HLa) and S-donor Cyanex 301 (HLb). We explored the coordination and complexing nature of Mo(VI) with HLa and HLb using scalar relativistic density functional theory. The electrostatic potentials and frontier molecular orbitals of HLa and HLb show that the former has stronger nucleophilic ability compared to the latter. All the MoO22+ complexes with HLa and HLb are tetra-coordinated structures. The values of Wiberg bond indices (WBIs) indicate that the Mo-S bonds have more covalency than Mo-O bonds. The energy decomposition analysis reveals that the interaction between MoO22+ ion with HLa is stronger than that with HLb, which is also supported by the thermodynamic energy. The thermodynamic energy indicates that [MoO2(H2O)2(NO3)]+ is the dominant initial species and reaction [MoO2(H2O)2(NO3)]++HL → [MoO2L(NO3)] + H++2H2O is the most preferred in the extraction process. This work elucidates the electronic structures and complexing nature of MoO22+ with Cyanex 272 and Cyanex 301 ligands and provides the useful theoretical information on designing acidic phosphorous extractants of MoO22+.

Progress in developing the novel extractants for rare earths

<p indent=0mm>The separation of rare earths is the key joint between the rare earth resources and high-performance functional materials of rare earth. Because most rare earth products were produced by solvent extraction, the performance of extractants is crucial to the efficiency of the extraction and separation of rare earths. In this review, the progress in the development of novel extractants for rare earths in China in the past ten years is briefly reviewed with more attention on the work on dialkyl phosphinic acids (including symmetric- and asymmetric ones), amine-containing organophosphorous extractants and carboxylic acids.

Extraction of rare earth elements from waste products of phosphate industry

Rare earths are critical elements in our modern societies and the ever-increasing demand raises fears of supply risks in the coming years. This work dealt with the feasibility of extracting rare earth elements (REEs) from an industrial waste product from the exploitation of phosphate ores of “Djebel Onk” in Tébessa eastern region of Algeria. The solid residue was first leached at room temperature with three different inorganic acids (HNO3, H2SO4 and H3PO4) at various concentrations and leaching times. It was possible to recover almost 100% of La, Ce, Eu, Gd and Y with HNO3 3 N in 24 h. However, only about 10% of Yb were leached. The leachates were further treated with two organophosphorous extractants, trioctylphosphine oxide (TOPO) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) at various concentrations in chloroform. A virtually total extraction of Eu, Gd, Y and Yb was achieved with TOPO at 0.3 M. The extraction efficiency of light rare earth elements (LREEs), La and Ce, was only 38 and 55%, respectively. Very good selectivities between heavy rare earth elements (HREEs), and LREEs as well as between medium rare earth elements (MREEs) and LREEs were obtained but TOPO was unable to selectively separate HREEs from MREEs. Although D2EHPA led to lower REEs extraction efficiency than TOPO, it showed interesting performance for the selective separation of REEs into three fractions corresponding to LREEs (La and Ce), MREEs (Eu and Gd) and HREEs (Y and Yb).

Deep insights into the solution and interface behaviors in heavy rare earth extraction: A molecular dynamics study

Heavy rare earth extraction (HRE) is a complex process involving extractant partition, complexation at metastable oil-water interface and cation separation from aqueous phase to organic phase. Beyond the coordination chemistry of the HRE extracted complex, the solution and interfacial behaviors can be crucial to extractant distribution, orientation and reactivity of ionic species for understanding and further improving the extraction performance. We report a molecular dynamics investigation on dilute and concentrated solutions of four acidic organophosphoric extractants (P507, P204, P227 and Cyanex272) in pure oil phase and oil-water biphasic systems for purpose of depicting solution and interface behaviors, which has been a cornerstone of chemistry in solvent extraction and separation. We can intuitively find that the single extractant promotes the interface movement. When the extractants get concentrated in organic phase, they diffuse and aggregate to dimers and trimers. In oil-water biphasic system, most of the extractants tend to migrate to the interface and remain an excess adsorption phenomenon, where –OH groups point towards water and are ready to capture an approaching HRE cation. Some important findings of different extractants are determined by theoretical simulation, such as interfacial activity, residual water number in equilibrated organic phase and capture time of HRE cation. These simulated quantitative features are in good agreement with the experiments of interfacial tension, phase separation and kinetic extraction. The results indicate the key role of the amphiphilic moiety, the oxygen atoms of P–O ester linkages and the hydrophobicity of P–C ester linkages of extractants in the HRE extraction process. This MD study could provide a straightforward approach to comprehensively evaluate and design the extractants for liquid-liquid solvent extraction in future.

Molecular Insights into Water Clusters Formed in Tributylphosphate-Di-(2-ethylhexyl)phosphoric Acid Extractant Systems from Experiments and Molecular Dynamics Simulations.

Di-(2-ethylhexyl)phosphoric acid (D2EHPA) and tributylphosphate (TBP) are two of the most studied and researched organophosphorous extractants. D2EHPA is an acidic extractant, offering both hydrogen bond donor and acceptor sites while TBP, a neutral extractant, only offers a single acceptor site per molecule. In spite of this, it is observed that 1 M D2EHPA in dodecane is a poorer extractant for water than 1 M TBP in dodecane. The objective of present work is to look into the molecular interactions that cause such behavior. Experiments were carried out with varying molar ratios of TBP and D2EHPA in the organic dodecane phase. Total extractant concentration was kept constant at 1 M with dodecane as diluent. Water extraction was quantified by measuring the moisture content of the organic phase after equilibration. 1H and 31P NMR spectra of the organic phase samples were recorded to study the change in the chemical environment upon extraction. Small angle X-ray scattering data of water saturated extractant phases were analyzed for the possibility of a reverse micellar aggregate formation. Molecular dynamics simulations could calculate free energies in quantitative agreement with experiments. Experimental and simulation studies showed that aggregation in the organic phase was promoted by the presence of water. This combined approach, of experiments and simulation, has shown that water is indispensable for the formation of ordered aggregates of extractants in nonpolar organic solvents. It is seen that, in the organic phase, around 80% of water's hydrogen bonds are with extractant molecules rather than with itself. The analysis clearly indicates that, rather than forming an aqueous core surrounded by extractant, water acts as a bridge between extractant molecules.

Comparative study on Ce (III) and La (III) solvent extraction and separation from a nitric acid medium by D2EHPA and Cyanex272

The solvent extraction of Cerium(III) and Lanthanum(III) from nitric acid solution using the organophosphorous extractants Di-(2-ethyl hexyl) phosphate (D2EHPA) and di-2,4,4- trimethylpentyl phosphoric acid (Cyanex272) in kerosene was investigated. In this study, the magnitude of the extraction of Ce(III) was found to be more significant with Cyanex272 than D2EHPA. D2EHPA was found to be a better extractant for La(III). Among the two extractants, Cyanex272 was used for the separation of Ce from La in three stages with an extraction efficiency of 90.2% for Ce. A 556 mg/L Ce solution was used for the scrubbing of La with an efficiency of ≈34%, which required multi stage scrubbing. The study of thermodynamic parameters such as enthalpy, entropy, and Gibbs free energy impart the exothermic and non-spontaneous process. The chemical speciation curves for lanthanum and cerium in the aqueous phase as a function of pH showed that the free La(III) and Ce(III) metal ion species were largely predominate between a pH = 0 and pH = 7.

Solid phase extraction of uranium from phosphoric acid: kinetic and thermodynamic study

Abstract There is a high interest to develop suitable solid phase extractants for uranium separation from aqueous solutions in order to reduce cost and enhance the efficiency. This paper describes solid phase extraction of uranium(VI) from aqueous phosphoric acid solution using MCM-41 based D2HEPA-TOPO organophosphorous extractants. The mixture of D2HEPA (di-2-ethyl-hexylphosphoric acid) and TOPO (tri-n-octylphosphine oxide) was impregnated into the pores of MCM-41 and the synthesized sorbent was fully characterized. The influences of different factors such as synergistic mixture ratio, phosphoric acid concentration, mixing time and temperature were investigated. The results showed that 90% of uranium(VI) extraction can be achieved within 5 min, using D2HEPA-TOPO@MCM-41 (mass ratio 2:1 w/w) from 1 M phosphoric acid containing 64 ppm of uranium at room temperature. High adsorption capacity of uranium(VI) have been achieved at the mentioned conditions. The rate constant for the chemical adsorption of uranium(VI) was 0.988 g mg‒1 min‒1 calculated by the pseudo-second order rate equation. The obtained thermodynamics parameters showed that uranium(VI) adsorption from H3PO4 is an exothermic and spontaneous process.

Extraction Behaviors of Heavy Rare Earths with Organophosphoric Extractants: The Contribution of Extractant Dimer Dissociation, Acid Ionization, and Complexation. A Quantum Chemistry Study.

Heavy rare earths (HREs), namely Ho3+, Er3+, Tm3+, Yb3+ and Lu3+, are rarer and more exceptional than light rare earths, due to the stronger extraction capacity for 100 000 extractions. Therefore, their incomplete stripping and high acidity of stripping become problems for HRE separation by organophosphoric extractants. However, the theories of extractant structure-performance relationship and molecular design method of novel HRE extractants are still not perfect. Beyond the coordination chemistry of the HRE-extracted complex, the extractant dimer dissociation, acid ionization, and complexation behaviors can be crucial to HRE extraction and reactivity of ionic species for understanding and further improving the extraction performance. To address the above issues, three primary fundamental processes, including extractant dimer dissociation, acid ionization, and HRE complexation, were identified and investigated systematically. The intrinsic extraction performances of HRE cations with four acidic organophosphoric extractants (P507, P204, P227 and Cyanex 272) were studied by using relativistic energy-consistent 4f core pseudopotentials, combined with density functional theory and a solvation model. Four acidic organophosphoric extractants have been qualified quantitatively from microscopic structures to chemical properties. It has been found that the Gibbs free energy changes of the overall extraction process (sequence: P204 > P227 > P507 > Cyanex 272) and their differences as a function of HREs (sequence: Ho/Er > Er/Tm > Tm/Yb > Yb/Lu) are in good agreement with the experimental maximum extraction capacities and separation factors. These results could provide an important approach to evaluate HRE extractants by the comprehensive consideration of dimer dissociation, acid ionization, and complexation processes. This paper also demonstrates the importance of the P-O bond, the P-C bond, isomer substituent, and solvation effects on the structure-performance relationship that can be used to guide molecular designs of HRE extraction in future.

Extraction and recovery of cadmium(Ⅱ) using phosphine-oxide, tris[(dibutylamino)methyl]-(7CI,8CI) from nitric acid solutions

ABSTRACTIn the present article, a new separation system was employed for the extraction of cadmium from nitric acid solutions for the first time. Phosphine oxide, tris[(dibutylamino)methyl]-(7CI,8CI),which contains nitrogen atoms and phosphorus atom in molecular, was used as extractant. The influence of the following parameters was investigated: the organic/aqueous phase ratio (O/A), pH, contact time, temperature, the concentration of extractant, cadmium (Ⅱ), sodium nitrate and sodium chloride. Results demonstrated that quantitative extraction of cadmium was feasible from 50 mg/L cadmium feed solution in a single stage at pH 3.0, 15 min and O/A phase ratio 1:5 with 20% extractant in cyclohexane diluent. The cadmium extraction isotherm under different cadmium ion concentrations was established. The loaded cadmium could be stripped by 4 mol/L ammonium chloride aqueous solutions. A contrast study was carried out, and the results indicated that phosphine oxide, tris[(dibutylamino)methyl] –(7CI,8CI), could take the place of commercial organo-phosphorous extractants in the process of cadmium(II) extractions for its effectivity, stability and low price.

On the Extraction of Vanadium (V) by Alkanols: A comparative Study of 1-pentanol and 3-methyl-1-butanol Isomers as Extractants for Vanadium (V) Extraction from Hydrochloric Acid Solutions

&lt;p&gt;Further to the previous study on the extractive recovery of V(V) from HCl solution by some alkanols, the extraction of V(V) from HCl solutions by 1-pentanol and 3-methyl -1-butanol (isomers) dissolved in n-heptane were investigated in the present study, still propelled by the need to proffering viable alternatives to the scarce and relatively costly organophosphorous extractants, and also compare the extraction efficiency of straight- and branched-chain extractants. At the studied pH range (0.5-4.0) with 1-penttanol as extractant, the percentage V(V) extraction (extraction efficiency, E%) reached optimum E%= 40.0 at pH of 3.0 and for 3-methyl-1-butanol, optimum E% was 36.7 at pH 2.0. Increasing concentration of HCl at the studied range (1.0 – 6.0 mol L&lt;sup&gt;-1&lt;/sup&gt;) was found to have an appreciable effect on percentage V(V) extraction. With both extractants, E% peaked at 5.0 and 6.0 mol L&lt;sup&gt;-1&lt;/sup&gt;HCl with values 70.0 and 66.7% for 1-pentanol and 3-methyl-1-butanol respectively.&lt;/p&gt;&lt;p&gt;With increase in the concentration of extractants, both extractants produced a trend of increased/decreased in E% for V(V), suggesting the extraction of two different species. The optimal percentage extraction values were 70.0 and 66.7% observed at log [1-pentanol] = 0.86 mol L&lt;sup&gt;-1&lt;/sup&gt; and log[3-methyl-1-butanol]=0.86 mol L&lt;sup&gt;-1 &lt;/sup&gt;, in that order. The determined enthalpy change. for 1-pentanol and 3-methyl-1-butanol systems were -80.4/120 kJ mol&lt;sup&gt;-1 &lt;/sup&gt;and -203.0/254.7 kJ mol&lt;sup&gt;-1&lt;/sup&gt; respectively, indicating exothermic/endothermic extraction processes. The isomer 3- methyl -1-butanol gave a higher extraction efficiency after a three-stage extraction (E% = 92.5) than 1-pentanol (E% = 83.4). Recycling experiment revealed both to be recyclable. From slope analysis, analytical and spectra data, the extracted complexes have been formulated as VO&lt;sub&gt;2&lt;/sub&gt;Cl.nROH and (VO&lt;sub&gt;2&lt;/sub&gt;Cl)&lt;sub&gt;m&lt;/sub&gt;.nROH (where m&amp;gt;&amp;gt; n) at low and high concentrations of extractant, respectively. On the whole, 3-methyl-1-butanol was assessed as fairly better as an extractant for vanadium (V) at lower temperature experimental conditions. The effect of methyl branched-chain played an insignificant role on the extraction.&lt;/p&gt;

Solvent extraction of cobalt and nickel from chloride solution by mixtures of acidic organophosphorous extractants and amines

In order to extract Co and Ni from the chloride solution with low initial pH (1–3), solvent extraction experiments were performed by employing the mixture of organophosphorous extractants (D2EHPA, PC 88A and Cyanex 272) and amine extractants (Alamine 336, Alamine 308, and Alamine 300). Among the studied mixtures, a mixture of Alamine 308 and Cyanex 272 showed the best efficiency for the selective extraction of Co (63%) over Ni from chloride solutions with an equilibrium pH of 4.9. Although Co was not extracted by each single extractant, the synergism was observed for Co extraction using this mixture. Moreover, it was possible to selectively extract Co over Ni using the mixture of Alamine 308 and Cyanex 272.

Separation of cobalt from nickel using novel ultrasound-prepared supported liquid membranes containing Cyanex 272 as carrier

The demand for cobalt has increased significantly in recent years due to its use in a wide variety of products and processes. Cobalt and nickel often accompany each other in nature and close physicochemical properties of both metals make their separation a complicated practical problem. Organophosphorous extractants have been widely used to separate cobalt from nickel. This paper presents the preliminary results obtained for separation of cobalt from nickel using Cyanex 272 containing supported liquid membranes prepared by a novel ultrasound-assisted method. The results show that this novel supported liquid membrane preparation method leads to higher separation factors than those described in the literature under similar separation conditions.

Recovery of manganese and zinc from waste Zn–C cell powder: Mutual separation of Mn(II) and Zn(II) from leach liquor by solvent extraction technique

Acidic organophosphorous extractants were screened for the mutual separation of Mn(II) and Zn(II), in a leach solution of waste Zn–C cell powder. This was done using a 2mol/L H2SO4 solution containing 2g/L glucose. Extraction characteristics of both metal ions in this mixture have been examined as functions of equilibrium pH. Although tech. and anal. grade D2EHPA are not so effective for the separation, PC88A, Cyanex 272, Cyanex 302 and Cyanex 301 are all promising for this purpose. Strippings of Mn(II) and Zn(II) from the extracted organic phases have been examined, using 0.25, 0.50 and 1mol/L H2SO4; and 1mol/L HCl, HNO3 and HClO4 at different phase ratios. H2SO4 appears to be the best stripping agent. A 1mol/L H2SO4 solution strips almost 100% of target metal ions in 10min, regardless of the extractant used. As ΔpH1/2=2.75 and as the max. separation factor (β)=1793 for Cyanex 302 at pH(eq)=4.0, a flow sheet has been developed for their mutual separations. Finally, classical precipitation methods have been adopted to obtain MnS and ZnS, which can be easily oxidized to MnO2 and ZnO, respectively.

Solvent Extractive Separation of Zirconium and Hafnium from Hydrochloric Acid Solutions by Organophosphorous Extractants and Their Mixtures with Other Types of Extractants

From 1 to 4 M HCl medium, zirconium was selectively extracted over hafnium by organophosphorous extractants (D2EHPA, PC88A, Cyanex 272). In order to increase the separation factor Zr/Hf, mixtures of organophosphorous extractants with amines (Alamine 336, Aliquat 336) or cationic extractants (Versatic acid 10, LIX 63) were employed in 1–4 M HCl medium. Mixtures with Versatic acid 10 and LIX 63 led to depression in the extraction percentages. But the mixture with LIX 63 was found to be the most effective in separating the two metals among the extractant systems tested in this study. The highest separation factor of around 9.5 was obtained with a mixture of 0.01 M LIX 63 + 0.05 M Cyanex 272 at HCl concentration of 2–4 M. The Zr and Hf were effectively stripped from the loaded mixture of LIX 63 + Cyanex 272 by sulfuric acid solution.

Synergistic extraction of Eu(III) with mixture of picrolonic acid and neutral organophosphorous extractants

Synergistic extraction of Eu(III) has been studied with a mixture of picrolonic acid (HPA) and neutral organophosphorous extractants; trioctylphosphine oxide (TOPO), triphenylphosphine oxide (TPPO) and tributylphosphate (TBP) in chloroform separately, from aqueous solution of pH 1-2, having ionic strength of 0.1 mol dm−3 (K+/H+, Cl−). Highest extraction (≥99 %) was achieved at pH 2 within five minutes using all the three mixtures. Composition of the extracted adduct has been determined as Eu(PA)3·2TOPO, Eu(PA)3·2TPPO and Eu(PA)3·TBP. The equilibrium constants (logKMix) for Eu(III) were calculated to be 4.54 ± 0.03, 5.69 ± 0.06 and 6.17 ± 0.04 using 0.01 mol dm−1 mixture of HPA and TBP, TPPO and TOPO respectively. Highest extraction was observed with HPA-TOPO, followed by HPA-TPPO and least with HPA-TBP mixture. Order of extraction becomes TOPO > TPPO > TBP. Separation factors for various metal ions have also been calculated and it is found that Eu(III) can be separated quantitatively from divalent metal ions. Pronounced synergism was observed in the range of 103–104 when the europium was extracted with the mixture of these extractants.

Solvent extraction of praseodymium(III) from acidic nitrate medium using Cyanex 921 and Cyanex 923 as extractants in kerosene

Solvent extraction of praseodymium(III) from acidic nitrate medium by the neutral organophosphorous extractants Cyanex 921 and Cyanex 923 in kerosene was studied. The effects of various parameters like equilibration time, nitric acid concentration, nitrate ion concentration, extractant concentration, temperature, and nature of diluents on the extraction behavior of Pr(III) were investigated. The extraction of 0.001 M Pr(III) was quantitative (93%) from the aqueous phase containing 0.001 M HNO_3 and 0.1 M KNO_3 using 0.5 M Cyanex 921/1 M Cyanex 923. On the basis of slope analysis, the compositions of the extracted species were formulated as Pr(NO_3)_3.2Cyanex 921 and Pr (NO_3)_3.Cyanex 923. The percentage of extraction of Pr(III) was found to decrease with increases in temperature. The standard enthalpy and entropy changes were negative owing to the complexation with decrease in randomness without a compensatory disruption of the hydration sphere of the metal ion. Mineral acids like hydrochloric acid (0.008 M) and sulfuric acid (0.03/0.02 M) were effective for the stripping of Pr(III) from the loaded organic phase with 0.5 M Cyanex 921/1 M Cyanex 923.

Alkanols for the Extraction of Vanadium (V) From Hydrochloric Acid Solutions

Extractive recovery of vanadium (V) from hydrochloric acid solutions using alkanols (1-butanol and 1-octanol) dissolved in n-heptane has been investigated by liquid-liquid extraction, propelled by the need to proffering alternatives to the scarce and relatively costly organophosphorous extractants. At the studied pH range (1.0-4.0), with 1- butanol as extractant, the percentage V(V) extraction (extraction efficiency, E%) reached optimum (E% = 63.3) at pH of 0.5, and for 1-octanol, optimum E% was 73.3 at pH 1.0.Increasing concentration of HCl at the studied range (1.0–6.0 mol L-1) was found to have an appreciable effect on percentage V(V) extraction. With both extractants, E% peaked at 6.0 mol L-1 HCl with values 86.7 and 70.0% for 1-butanol and 1-octanol, respectively. With increase in the concentration of extractants, both extractants produced a trend of increase/decrease in E% for V(V), suggesting the extraction of two different species. The optimal percentage extraction values were 76.7 and 96.7% observed at log[1-butanol] = 0.81 mol L-1 and log[1-octanol] = 0.49 mol L-1, in that order. The determined enthalpy change, ?H, for 1-butanol and 1-octanol systems were -19.9kJ mol-1 and -37.1 kJ mol-1, respectively, indicating exothermic extraction processes. On the number of required extraction stages, 1-octanol gave a higher extraction efficiency after three consecutive extractions (E% = 99.3) than 1-butanol (E% = 88.6). Recycling experiment showed 1-octanol as more recyclable than 1-butanol (Recycling coefficient R.C. = 1.0 for 1-octanol while R.C. > n) at low and high concentrations of extractant, respectively. On the whole, 1-octanol could be adjudged a better extractant for vanadium (V) under the prevailing experimental conditions.