Phosphonic Acid Mono 2-ethylhexyl Ester Research Articles

Recovery of rare earth elements and thorium from acid leaching residue of ionic rare earth concentrates

The acid leaching residue (ALR) of ionic rare earth (IRE) concentrates containing radioactive elements such as thorium (Th) is classified as low-level radioactive waste. ALR holds valuable strategic resources such as rare earth and Th, while improper long-term heaping storage of ALR poses a substantial environmental risk. This paper proposes a comprehensive process involving low-temperature roasting, hydrochloric acid leaching, single extractant enrichment, and stepwise stripping to recover rare earth elements and thorium from ALR. The achieved leaching efficiencies are 80.11% of LnY, 99.43% of Sc(III), and 98.67% of Th(IV) after the carbonization of the organic phase in the ALR through low-temperature roasting. Despite large amounts of acid and impurities present in the leachate, 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester (HEHEHP) still exhibits nearly 100% extraction efficiency for Sc(III) and Th(IV). The effective separation of LnY, Th(IV), and Sc(III) was achieved by implementing fractional extraction enrichment of Th(IV) and Sc(III), followed by Th(IV) removal through H2SO4 and Sc(III) removal via NaOH from the loaded organic phase. This scheme successfully achieves a recovery of RE and Th and offers a viable solution for the safe disposal of ALR.

Nano ZrO2 Synthesis by Extraction of Zr(IV) from ZrO(NO3)2 by PC88A, and Determination of Extraction Impurities by ICP-MS

High purity Zirconium (Zr) materials are essential in many components of nuclear reactors, especially fuel cladding tubes. Due to the matrix influence, determination of impurities in the Zr materials requires separation from the Zr matrix. Among extraction methods, solvent extraction is common and suitable for large-scale production. In this study, extraction capability of Zr(IV) by 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester (PC88A) was examined by FT-IR and UV of ZrO(NO3)2 salt, PC88A-toluene solvent, and Zr-PC88A-toluene complex. ZrO2 (obtained from Institute for Technology of Radioactive and Rare Elements—ITRRE), after being separated from the Zr matrix, was determined for impurities using internal standard (indium, In) by 50% of PC88A dissolved in toluene. Separation of impurities from the Zr matrix underwent two stages. First, one cycle of extraction of the Zr matrix and impurities in 3 M HNO3 using 50% PC88A/toluene was conducted. Second, impurities were scrubbed by 4 M HNO3 in two cycles. Results revealed that approximately 74% of Zr(IV) was separated to the organic phase and 26% remained in the aqueous phase. Determination of impurities after separation from the Zr matrix by ICP-MS using internal standard in revealed that the recovery of impurities achieved 95–100%. With the mentioned amount of Zr, the effect of the Zr matrix on the determination of elements by ICP-MS is negligible. Levels of impurities have relative standard deviations (RSD) of less than 6.9% and recovery of 88.6–98.8%. Therefore, the determination of impurities has high reliability and accuracy. The back-extraction of Zr(IV) in organic phase by 1 M H2SO4 has stripped about 99.5% of the Zr matrix back to the aqueous phase. Following this, NH3 was added to the solution containing Zr after back-extraction to form Zr(OH)4 which was then desiccated to produce ZrO2. X-ray Diffraction (XRD), Scanning and Transmission Electron Microscopy (SEM and TEM) images showed that the new ZrO2 product has spherical nanostructure with diameters of less than 25 nm, which is suitable for applications for the treatment of colorants, metal ions in wastewater sources and manufacture of anti-corrosion steel. In addition, the energy dispersive X-ray (EDX) of the new ZrO2 product showed that it has high purity.

Studies on the Separation and Recovery of Uranium from Phosphoric Acid Medium Using a Synergistic Mixture of (2-Ethylhexyl)phosphonic Acid Mono 2-Ethyl Hexyl Ester (PC-88A) and Tri-n-octylphosphine Oxide (TOPO)

This paper deals with studies on the extraction of uranium(VI) from phosphoric acid medium using (2-ethylhexyl)phosphonic acid mono 2-ethylhexyl ester and tri-n-octylphosphine oxide individually as well as from their synergistic mixture. Different extraction parameters were investigated. With an increase in phosphoric acid concentration in the aqueous phase, the distribution ratio (Du) was found to decrease in all the cases. Synergism was observed when a mixture of PC-88A and TOPO was used. The synergistic mixture in the mole ratio of 4:1 (1.80 M PC-88A: 0.45 M TOPO) in xylene was found to be most suitable for uranium extraction. Among the various strip liquors used, 5% (w/v) solution of (NH4)2CO3 was found to be the most suitable. Using a mixture of 1.8 M PC-88A and 0.45 M TOPO as the extractant system and 0.5 M ammonium carbonate as the stripping agent, uranium recovery was found to be better than 97% ± 3% in multiple contacts, (n = 2) from actual Davies Gray Waste while in case of wet phosphoric acid more than 52% ± 3% (n = 3) only could be recovered where n is the number of contacts.

Synergistic extraction of cerium from sulfuric acid medium using mixture of 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester and Di-(2-ethyl hexyl) phosphoric acid as extractant

Synergistic extraction of cerium(IV) from sulfuric acid medium using mixture of 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester(HEH/EHP, HL) and Di-(2-ethyl hexyl) phosphoric acid (HDEHP, HA) as extractant was investigated. The results indicated that the maximum synergistic enhancement coefficients were obtained at the mole fraction of HEH/EHP=0.6, and cerium(IV) was extracted into organic phase in the form of Ce(SO 4) 0.5HL 2A 2. A cation exchange mechanism was proposed for the synergistic extraction of Ce(IV). The equilibrium constants and thermodynamic functions such as Δ G, Δ H, and Δ S were determined in the extraction of Ce(IV) from sulfuric medium using mixture of HEH/EHP and HDEHP.

Synergistic extraction of praseodymium with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester and 8-Hydroxyquinoline

The synergistic extraction of Pr(superscript 3+) from hydrochloric medium using mixture of 2-ethylhexyl phosphonic acid mono2-ethylhexyl ester (P507, HL) and 8-Hydroxyquinoline (HQ) in heptane was investigated. The effect of equilibrium of aqueous acidity on extraction of Pr(superscript 3+) was discussed. The effect of extractant concentraction, different diluents, equilibrium time and acetate ion concentration on extraction reaction were also studied. With a method of double-logarithmic slope, composition of the extracted species on 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester and 8-Hydroxyquinoline was derived. The result shows that the synergistic extraction system not only overcomes emulsification of 8-Hydroxyquinoline, but also shows perfect capacity of synergistic extraction. The largest synergistic enhancement factor can be calculat ed to be 5.49 at pH 3.6 for Pr(superscript 3+).

Selective separation of Cu(II), Zn(II), and Cd(II) by solvent extraction

An experimental investigation was presented on the separation of Cu(II), Zn(II), and Cd(II) from a rich sulfate leachate of zinc slag by solvent extraction. The results of orthogonal experiments indicate that LIX 984N is highly selective and very efficient in the extraction of Cu(II), and the analysis of variance indicates that the sequence of parameters according to their influence on the separation efficiency is phase ratio > LIX 984N concentration > pH value > extraction time. The optimal condition for copper extraction is obtained as 25% of LIX 984N concentration, 7 min of extraction time, 3:2 of phase ratio O/A, and pH = 1.7. The separation of Zn(II) and Cd(II) was performed after the copper extraction from the raffinate. Comparative analysis of the separation with di-2-ethylhexyl phosphoric acid (D2EHPA), D2EHPA- tributylphosophate (TBP) synergistic extracting system, and 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester (HEHEHP) was made at pH = 2.0. It is demonstrated that the extraction efficiency with D2EHPA is improved after being saponified by sodium hydroxide, and D2EHPA-TBP synergistic extracting, as well as HEHEHP, has a superior selectivity to Zn(II) over Cd(II).

Separation of Gallium and Arsenic in Wafer Grinding Extraction Solution Using a Supported Liquid Membrane that Contains PC88A as a Carrier

Wafer grinding extraction solution was passed through a supported liquid membrane (SLM) that contained PC88A (2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester) as a carrier, to separate gallium from arsenic by selective permeation. The SLM separation process was conducted under various conditions. The kind of membrane supporter, the pH of the feed, the feed concentration, and the HCl content in the strip governed the concentration of gallium and arsenic in the strip phase. The conditions determined as optimal in the laboratory test were used to perform the pilot test. Well separation between gallium and arsenic was performed in both laboratory and pilot tests. Hydrophobic membrane polytetrafluoroethylene (PTFE) with 0.2 μm pores was the best of three membrane supporters. The most efficient separation was obtained using an acidic feed (pH at 1.8) with 1000 ppm gallium. Over a 12-h period of stripping, the striped Ga concentration increased with the HCl concentration from 0.5 to 2.0 M and then leveled off. The recovery rate in the pilot test exceeded that on the laboratory scale because the membrane area was greater. The pilot test yielded a high recovery percentage of gallium (at 91%) and a low recovery of arsenic (merely 1.3 ppm) in the strip over 72 h.

Solvent extraction separation of gallium(III) with 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester (PC-88A)

A rapid method for the extraction separation of gallium(III) with PC-88A in toluene has been studied. The extraction of gallium(III) was found to be quantitative with 0.025 M PC-88A in toluene in the pH range 2.0–3.0. Gallium(III) extracted in the organic phase was stripped with 2.0 M HCl and was determined spectrophotometrically by the PAR method. Effects of parameters such as reagent concentration, time to achieve equilibrium, various diluent and diverse ions on the extraction of gallium(III) were also studied. The stoichiometry of the extracted species of gallium(III) was determined on the basis of slope analysis method. The extraction reaction proceeds via a cation exchange mechanism and the extracted species is in the GaL 33HL form. Temperature dependence of the extraction equilibrium constant was also examined to estimate the apparent thermodynamic functions Δ H, Δ G and Δ S for extraction reaction.

MECHANISM OF THE EXTRACTANT LOSS IN LANTHANIDE EXTRACTION PROCESS WITH SAPONIFIED ORGANOPHOSPHORUS ACID EXTRACTION SYSTEMS — II: FORMATION OF AQUEOUS AGGREGATES

ABSTRACT Organophosphorus acids, including di(2-ethylhexyl) phosphoric acid (D2EHPA), 2-ethyIhexyI phosphonic acid mono 2-ethylhexyl ester (PC88A), and di(2-ethylhexyl) phosphinic acid (P229) form reversed micelles (d=20-100A) or water-in-oil (w/o) microemulsions (d=100-2000 A) in n-heptane when they are saponified with concentrated alkalis, such as NaOH, KOH and NH3H2O. After equilibrating with water or solution containing europium, some extractant and diluent in the saponified organic phase transfers into the aqueous phase, and some water solubilized in the w/o microemulsion returns to the aqueous phase. Dynamic light scattering (DLS) results indicate that aggregates within the range of micelles or microemulsions are formed in the equilibrated aqueous phase. The normal micelle or o/w microemulsion has a non-polar core that solubilizes n-heptane. Therefore, the formation of aqueous aggregates leads to extractant and diluent loss in the extraction procedure. FT-IR spectra also confirm the presence of extr...