HYDROFLUORIC ACID EXTRACTION BY TBP AND BY AMINES: MECHANISM,SPECIES FORMED AND UNIQUE PROPERTIES AT HIGH ACID TO AMINE MOLAR RATIOS

Analysis of data concerning HF extraction by amines reveals a change in extraction mechanism when HF/amine molar ratio in organic phase (Z) reaches 2. Up to this point extraction is by ion-pair formation and after it by H-bonding. As a result, the two HF molecules initially extracted differ in nature from subsequent ones. The change in mechanism explains why seemingly unrelated properties such as water co-extraction dilution and diluent effects, selectivity and viscosity - all change when amine bifluoride composition is attained. Similar change in extraction of other mono-basic acids occurs at Z=1. The system with Z>2 for HF is equivalent to that with Z>1 for other mono-basic acids and to that of extraction by TBP. It therefore provides a model for extraction from concentrated aqueous solutions.     

SYNERGISTIC EXTRACTION OF ZINC(II) BY MIXTURES OF PRIMARY AMINE N1923 AND CYANEX272

ABSTRACT

The extraction of zinc(II) and cadmium(II) from chloride solution by mixtures of primary amine N1923 and Cyanex272 (HA) was studied. The synergistic effect was observed for the extraction of zinc(II) while no synergistic effect for cadmium(II), which makes it possible to separate zinc(II) and cadmium(II) with the mixtures. The results showed that zinc(II) was extracted as (RNH₃Cl)₃·ZnClA instead of ZnA₂·2HA which was extracted by Cyanex272 alone. The extraction mechanism was discussed and the formation constants and thermodynamic functions were determined. The separation factors between zinc(II) and cadmium(II) were calculated.     

EXTRACTIVE SEPARATION OF URANIUM AND ZIRCONIUM SULFATES BY AMINES

ABSTRACT

This paper describes an amine extraction process for zirconium and uranium separation. The behaviour of an extraction system containing uranium (VI) sulfate, zirconium (IV) sulfate, 0.2 and 0.5 M sulfuric acid (as the original aqueous phase), tertiary amine tri-n-lauryl- amine or primary amine Primene JMT in benzene (as the original organic phase) is discussed on the basis of equilibrium data.

The measured dependences show that the degree of extraction of zirconium at the sulfuric acid concentration of 0.5 M and above is only slightly affected by a presence of uranium in solution. From this surprising behaviour it follows that zirconium may be employed for the displacement of uranium from the organic phase. This effect is more pronounced with the primary amine Primene JMT than with TLA.     

SYNERGISM IN THE EXTRACTION OF ZINC(II)AND CADMIUM(II) WITH SOME LOWER FATTY ACIDS IN THE PRESENCE OF AMINES AND THEIR SEPARATIONS∗

Abstract

Synergism in the extraction of Zn(Il) and Cd(II)with chloroform solution of propionic, butyric and valeric acids in the presence of n-butylamine, dibutylamine, tributylamine, β-picoline, pyridine and quinoline is reported The effect of various parameters affecting extractions has been investigated The compositions of synergistic adduct extracted into the organic phase have been proposed on the basis of slope analysis method. In general the species have been represented as MA2.2HA.B (aliphatic amine system and MA₂.2HA.2B (heterocyclic amine system), where M = zn(Il)/CdII), HA = acid and B = amine. On the basis of extraction constant (K_ex) values the relative effectiveness of different amines as synergists has been compared. Based on the extraction data some separations of metal ions have also been reported with fairly high separation factor (β).     

THE EXTRACTION OF COBALT(II) FROM A THIOCYANATE MEDIUM BY SOME DIAMINE AND MONOAMINE EXTRACTANTS DISSOLVED IN 5% ISODECANOL - BENZENE

The tertiary amine extractants N,N,N’,N’-tetra-n-octylethylenediamine, N,N-di-n-octyl-2-(aminomethyl)pyridine and Alamine 336 were used to extract cobalt(II) from a thiocyanate medium. The extraction equilibria were identified and the extraction constants for these equilibria are presented.

Thiocyanic and sulphuric acid extraction was investigated. The protonation constants of the tertiary amines with these acids are reported.

The potential of the chelate mode, displayed by tertiary diamine extractants, was evaluated. The extraction properties of tertiary diamine extractants were demonstrated to be superior to a tertiary monoamine extractant, Alamine 336.     

Effect of acetic acid on the leaching behavior of impurities in metallurgical grade silicon

To explore the potential of acid leaching in purification metallurgical grade silicon (MG-Si) for solar cells, the effect of acetic acid on the leaching behavior was investigated in the present work by focusing on the behavior of impurities affected by the addition of acetic acid to a conventional acid mixture composed of hydrochloric acid and hydrofluoric acid. The etching results reveal that the HCl–HF–CH₃COOH mixture is a better lixiviant for dissolving impurity inclusions in MG-Si. The extraction yield of impurities in HCl–HF–CH₃COOH leaching was found to increase by 7% compared to conventional HCl–HF leaching.     

Extraction of Fatty Acids from Noncatalytically Cracked Triacylglycerides Using Aqueous Amines

It has been reported that a basic aqueous solution was effective in extracting short chain C₂–C₆ fatty acids from noncatalytically cracked triacylglyceride oils. However, the extraction efficiency was not optimal over the entire range (C₂–C₁₂) of acids present in the cracking reactor organic liquid product (OLP). Therefore, an additional study was performed to explore the efficiency of solvent extraction using aqueous amines for this application. Based on the screening of several amines, two tertiary amines, trimethyl amine (TMA), and dimethyl ethanolamine (DMEA), were selected and evaluated. The extraction conditions were optimized with respect to several factors: temperature, amine concentration, and the amine-to-OLPratio (amine/OLP). Under optimal conditions, both TMA and DMEA were effective in extracting a wide range of organic acids, with TMA removing 93% of total acids and DMEA removing 100% of total acids. The amine/OLP was found to be a significant factor, as was the concentration of the amine solution. Temperature was not found to be a significant factor over the range studied. These results provide a basis for the development of a scalable, continuous process to produce a variety of C₂–C₁₂ fatty acids from biological sources.     

EFFECT OF BORIC ACID ON THE EXTRACTION OF BASTNASITE LEACHING LIQUOR BY CYANEX 923

The effect of boric acid on the extraction of bastnasite leaching liquor by Cyanex 923 was studied. Boric acid wasnt extracted alone by Cyanex 923 and didnt influence the cerium(IV) extraction. But it can enhance the extraction of hydrofluoric acid evidently and came into organic phase in form of (HF)(H3BO3).(Cyanex 923).     

GOLD EXTRACTION FROM THIOSULFATE SOLUTIONS USING MIXED AMINES

ABSTRACT

The extraction of gold from thiosulfate solutions with amine oxide and its mixture with amines has been studied, the results show that the amine oxide (TRAO) has a higher extraction ability for gold compared with tertiary amine. It can extract gold from neutral and weakly alkaline thiosulfate solutions, similar to the primary amine as extractant. The addition of TRAO enhances the extent of gold extraction with primary, secondary, and tertiary alkyl amines, respectively. The stoichiometry for the extraction of gold from thiosulfate solutions using the mixed solvent containing the primary amine N₁₉₂₃ and the amine oxide TRAO was investigated using slope analysis. The compositions of the gold extraction species with mixed organic solvents are proposed.     

Synergism and Separation Factors in Lanthanide Extraction with Mixtures of Chelating Extractant and Amine Salts in C6H6

Abstract

The solvent extraction of Pr, Gd, and Yb with 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one (HP) and an amine salt (AmHA) has been studied. The composition of the extracted species has been determined as (AmH)[LnP₄]. The values of the synergistic coefficients and separation factors have been calculated. The effect of the amine salt on the extraction and separation of lanthanides has been discussed.     

Quartz Dissolution as Influenced by pH and the Presence of a Disturbed Surface Layer

Quartz particles (10 to 2 microns in diameter, produced by grinding) released 45 ppm of SiO₂ to a buffer solution of pH 7 during a 48 hr period. The grinding of quartz particles produced a disturbed surface layer with solubility properties intermediate between crystalline quartz (6 ppm SiO₂) and amorphous silica (120 ppm SiO₂). Removal of the disturbed layer by treatment with 1N HF lowered the SiO₂ dissolution from 45 to 3 ppm. Use of 12N HF decreased the amount of SiO₂ dissolved to 2 ppm, a result found to coincide with a preferential dissolution of the finer quartz particles in addition to the removal of the disturbed surface layer. The rate of dissolution of SiO₂ from quartz particles, subsequent to treatment with 1N HF, increased with decrease in particle size, from 1 to 3 ppm for quartz particles 50 to 20 microns in diameter to 30 to 44 ppm for particles 2 to 0.2 microns in diameter, during each of three consecutive 14-day extractions with pH 7 buffer solution. The amount of SiO₂ dissolved from quartz in buffer solutions increased in the pH range of 4 to 10, from 0.6 ppm of SiO₂ at pH 4 to 19 ppm at pH 10 during a 14-day period of extraction from quartz particles, 10 to 2 microns in diameter. Quartz particles, subsequent to the removal of the disturbed surface layer, removed SiO₂ from pH 4 and pH 8 buffer solutions prepared with more SiO₂ in solution than would be released from quartz in the respective solution.     

EXTRACTION OF URANYL IONS BY SYNERGISTIC MIXTURES OF THENOYLTRIFLUOROACETONE AND MACROCYCLIC DONORS

A linear polyether, 1, 13-bis[8-qulnoly]-l,4,7,10,13-pentaoxa-trldecane (K-5) and an aza-crown ether, 4,13-didodecyl-1,7,10,16-tetraoxadiazacyclooctadecane (K22DD) when combined with thenoyltrlfluoroacetone (HTTA) have been shown to exhibit a synergistic effect on the extraction of uranyl ion. The effects of the addition to the organic phase of K-5, K22DD, and tert-butylcyclohexyl-15-crown-5 (15-C-5) on the extraction of UO₂ ⁺² by HTTA in chloroform from 0.5 M NaNO₃ at 25°C have been measured. The results indicate the extraction is enhanced by the formation of an adduct, UO₂(TTA)₂S for K-5 and K22DD. No enhancement of the extraction was seen with the crown ether. The organic phase stability constants for both K-5 and K22DD were evaluated and found to be similar in magnitude. These results suggest that the major factor in the formation of the synergistic adduct is the presence of the nitrogen atom in the synergist.     

Development of biocompatible NaGdF4: Er3+, Yb3+ upconversion nanoparticles used as contrast agents for bio‐imaging

Upconversion nanoparticles with special fluorescence and magnetic properties have been considered an alternative contrast agent for multiple bio‐imaging techniques. It is important to understand the effects of the surface properties and dosage of upconversion nanoparticles on both the magnetic resonance (MRI) image and the photoluminescence spectrum. Here, NaGdF₄: Er³⁺, Yb³⁺ upconversion nanoparticles (UCNPs) modified with amine functional group were produced through a one‐pot thermal decomposition. The average length of the cubic UCNPs is estimated at 53 ±13 nm. The effect of the dosage of amine modified UCNPs on the MRI image is investigated. The T₁ and T₂ relaxivities of the amine modified UCNPs in agarose gel at 3 T are r₁ = 6.79 ±0.14 and r₂ = 17.0 ±0.18 (mmol/L)^?1 s^?1, which are comparable to the relaxivities of commercially available MRI contrast agents. In addition, the photoluminescence of the amine modified UCNPs at low concentrations < 150 µg/mL are further investigated with the excitation wavelength (λ_ex) at 980 nm. The internalization of the amine modified UCNPs cultured with human umbilical vascular endothelial cells (HUVEC) is observed by the fluorescence imaging. Meanwhile, T₁‐weighted MRI imaging of HUVEC cells treated with amine modified UCNPs at 10 µg/mL can be obtained. No significant toxic effect on cells is found when the concentration of the amine modified UCNPs is < 300 µg/mL. This study indicates that a low concentration of amine‐modified NaGdF₄: Er³⁺, Yb³⁺ UCNPs can be used as the contrast agent for both fluorescence imaging and magnetic resonance imaging.     

liquid–liquid extraction of lactic acid with Alamine 336

The extraction of lactic acid (HL) from aqueous solutions by Alamine 336 (B) dissolved in toluene was studied. Experiments were performed in the temperature range of 25–60°C and for two amine concentrations of 20 and 40% (v/v) in toluene. The extent to which the organic phase (amine + toluene) may be loaded with lactic acid is expressed as a loading ratio, Z = C_HL /C_B. Z values are independent of the amine concentration and, hence, the extracted complex contains only one molecule of amine. Z decreases with increasing temperature. Experimental results indicate that the system presents overloading, i.e. Z > 1. The extraction equilibrium may be interpreted as a result of consecutive formation of three acid–amine species with stoichiometries of 1:1, 2:1 and 3:1.     

Modified supercritical CO2 extraction of amine template from hexagonal mesoporous silica (HMS) materials: Effects of template identity and matrix Al/Si molar ratio

In this work, the primary amine template has been extracted from freshly synthesized hexagonal mesoporous silica (HMS) materials by means of modified supercritical carbon dioxide at 60–85 °C under 10.0–20.0 MPa. The influences of amine identity and matrix Al/Si ratio on the extraction efficiencies and structural properties of HMS thus obtained are investigated in detail. The results show that the extraction efficiency is strongly dependent on the pore size of the HMS materials produced by five different templates. For aluminium-incorporated samples, the extraction efficiency is observed to decrease with the Al/Si molar ratio since as the Al/Si molar ratio increases, more amine will get protonated and the matrix/template interactions become stronger, subsequently rendering the extraction more difficult and the efficiency decrease. The formic acid modifier has resulted in better extraction performance than methanol, yielding higher extraction efficiencies. The SFE-treated materials exhibit better structural properties like higher pore volume and specific surface area as compared to those prepared by conventional calcinations. Besides, results of pyridine adsorption and conversion of 2-propanol to propylene suggest that the SFE-treated HMS materials may have higher acidity than the directly calcined samples.     

Recovery of Fumaric Acid from Industrial Wastewater by Chemical Extraction and Stripping

Abstract

The study on chemical extraction and stripping for the recovery of fumaric acid from low concentration organic acid wastewater has been carried out. The parameters influencing the extraction efficiency were investigated, including extractant concentration, the initial pH, the volume ratio of water to oil (W/O), the extraction temperature, and the concentration of n‐octanol. The heat effect of the extraction process, the formation of acid‐amine complexes, and the corresponding equilibrium constant were determined. In the optimum condition that kerosene/N₇₃₀₁/n‐octanol was 2:2:1, pH was 0.5, W/O was 1:1, and the temperature was 303K, through chemical extraction and stripping, the COD_cr value of fumaric acid wastewater decreased from 71040 mg/l to 8411 mg/l, and the overall COD_cr removal rate reached 88.16%, and the extraction efficiency of fumaric acid was 70.67%. The extractant was regenerated by a stripping process with 2% NaOH, and the stripping rate almost arrived at 100%. The regenerated extractant was cycled seven times without decreasing extraction efficiency and the stripping rate. And fumaric acid was obtained by adjusting the pH of the salt from stripping. After extraction, the fumaric acid wastewater can be further treated by oxidation or biodegradation to environmentally acceptable levels.     

Removal of perfluorooctanoic acid from water by adsorption on high surface area mesoporous materials

Removal of perfluorinated alkylated substances (PFAS) such as perfluorooctanoic acid (PFOA) from aqueous solution is an actual topic in light of their widespread diffusion and their persistence in the environment. The process of adsorption has been identified as an effective technique to eliminate PFAS in water, however the process efficiency strongly depends on the adsorbents employed (silica, alumina, activated carbon, layer doubled hydroxides). In this work three nanostructured mesoporous silica materials of similar pore diameter (~4 nm) featuring high surface area (~900 m²/g) and high pore volume (0.7–1.0 mL/g) were evaluated in PFOA removal: calcined MCM-41 (MCM-41c), calcined hexagonal mesoporous silica (HMSc) and HMSe obtained after ethanol extraction of the amine templates from HMS. Sorption kinetics and isotherms were performed at PFOA concentrations from 10 µg/L to 10 mg/L. It appeared that HMSe showed much faster and higher adsorption capacity for PFOA than the other tested adsorbents (MCM-41c and HMSc) whatever the pH of the solution (5 < pH < 9). Thermogravimetric analysis of HMSe evidenced that the ethanol extraction of the templating amines was not complete (70 %) and HMSe possessed some remaining hexadecylamine (HDA) (0.08 mol amine per mol SiO₂) on the surface conferring some hydrophobic properties to the adsorbent and also some probable complex formation between anionic PFOA^? and protonated HDA. Indeed, the incomplete amine extraction is surely due to the presence of protonated HDA in strong electrostatic interactions with SiO^? avoiding their removal by simple ethanol extraction as for H-bonding amine with Si–OH groups. Considering both adsorption isotherms and adsorption kinetics, PFOA could be efficiently removed from contaminated water in a wide range of concentration by an environmental friendly adsorbent as HMSe.     

Extraction of antimony and niobium with tributyl phosphate from fluoride-ammonium solutions

The purification of niobium from antimony impurity via extraction with tributyl phosphate from solutions of the HF + NH₄F mixture has been studied. It has been established that at an HF + NH₄F content equal to 7–16 mol/L and an NH₄F concentration of 30% in the mixture, Sb extraction hardly changes (70–80% for one stage), and Nb coextraction abruptly decreases to values of less than 0.5%.     

EXTRACTION OF METAL-OXALATE COMPLEXES BY DICATIONIC ANION-EXCHANGE EXTRACTANTS

The extraction of oxalate complexes of divalent metal ions (Zn²⁺, Cd²⁺ ) by dicationic anion-exchange extractants, polymethylenebis(trioctylphosphonium)s (abbreviated as C_nBP), was studied. The shorter the length of methylene-chain connecting two cationic centers within an extractant molecule, the higher was the extractant capability, i. e., the extraction ability of extractants decreased in the order: C₂- > C₃- > C₄- > C₅- > C₆- > C₈- > C₁₀- > C₁₂BP. The entirely inverse order was obtained in the extraction of metal-halide complexes (M^IICl₄ ²-) and metal-cyanide complexes (M II(CN) ₄ ²-). The extraction abilities of monocationic extractants were inferior to even that of the least efficient one among the dicationic extractants. The extraction equilibrium was also studied.     

Tantalite treatment process at the Congo deposit and columbite at the Zashikhinsk deposit

The conditions of tantalite (Congo deposit) and the decomposition of columbite (Zashikhinsk deposit) using an HF and H₂SO₄ mixture when heated to 80°C have been found. The extraction of Ta and Nb into solutions achieved levels of more than 99% and ～94% for tantalite and columbite, accordingly. It has been found that operation with filtrates that were obtained during the decomposition of concentrates and sent for the Ta and Nb extraction was radiation-proof. Schemes for the Ta and Nb separation and cleaning by octanol-1 extraction have been proposed.