Studies on the Recovery of Uranium from Phosphoric Acid Medium by D2EHPA/n-Dodecane Supported Liquid Membrane (original) (raw)
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Hydrometallurgy, 2009
This paper describes the extraction of uranium from aqueous phosphoric acid medium using (2-Ethyl hexyl) Phosphonic acid, mono (2-ethyl hexyl) ester (PC88A) and tri-n-butyl phosphate (TBP) individually as well as their synergistic mixture in different diluents. The various experimental parameters are investigated to optimize optimise the suitable extraction conditions. Results indicate that a synergistic mixture of 0.90 M PC88A + 0.15 M TBP in xylene, can be used for the extraction of uranium from low phosphoric acid medium. Back extraction studies reveals that among all the common strippants used, 0.50 M solution of (NH 4 ) 2 CO 3 was most suitable. The synergistic mixture of 0.90 M PC88A + 0.15 M TBP as extractant system and 0.5 M (NH 4 ) 2 CO 3 as strippant is used to recover uranium from a conditioned wet process phosphoric acid and from actual radioanalytical waste generated during uranium analysis by modified Davies-Gray method. The recovery is found to be around 80% from conditioned WPA whereas better than 90% from modified Davies-Gray waste.
Separation Science and Technology, 2009
This paper describes the extraction of uranium from aqueous phosphoric acid medium using (2-Ethyl hexyl) Phosphonic acid, mono (2-ethyl hexyl) ester (PC88A) and tri-n-butyl phosphate (TBP) individually as well as their synergistic mixture in different diluents. The various experimental parameters are investigated to optimize optimise the suitable extraction conditions. Results indicate that a synergistic mixture of 0.90 M PC88A + 0.15 M TBP in xylene, can be used for the extraction of uranium from low phosphoric acid medium. Back extraction studies reveals that among all the common strippants used, 0.50 M solution of (NH 4 ) 2 CO 3 was most suitable. The synergistic mixture of 0.90 M PC88A + 0.15 M TBP as extractant system and 0.5 M (NH 4 ) 2 CO 3 as strippant is used to recover uranium from a conditioned wet process phosphoric acid and from actual radioanalytical waste generated during uranium analysis by modified Davies-Gray method. The recovery is found to be around 80% from conditioned WPA whereas better than 90% from modified Davies-Gray waste.
Separation Science and Technology, 2010
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 (NH 4 ) 2 CO 3 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% AE 3% in multiple contacts, (n ¼ 2) from actual Davies Gray Waste while in case of wet phosphoric acid more than 52% AE 3% (n ¼ 3) only could be recovered where n is the number of contacts.
Extraction of Uranium(VI) using D2EHPA/TOPO based supported liquid membrane
Journal of Radioanalytical and Nuclear Chemistry, 2009
This work concerns the extraction of U(VI) using supported liquid membrane (SLM) by di-(2-ethylhexyl) phosphoric acid (D2EHPA) and tri-n-octyl phosphine oxide (TOPO) with polyvinylidene difluoride (PVDF) as a membrane support. The influence of ionic strength (S), stirring rate (V) and extraction time (t) were studied. The effect of membrane thickness on the permeability and extraction yield of uranium was investigated. A comparative study was carried out using a 2 3 full factorial design between SLMs with one membrane and two membranes, and to achieve the best conditions of recovery procedure, obtaining the mutual interaction among variables and optimizing these variables. The recovery of U(VI) is almost quantitative, and the supported liquid membrane with two membranes in series is effective.
Uranium extraction from purified wet process Jordanian phosphoric acid: a development study
Hydrometallurgy, 2000
A study on the physical properties, liquid-liquid equilibrium and the performance of a pulsed sieve plate column was conducted using the system: Jordanian purified filter phosphoric acid Ž . 28% P O -uranium-0.5 M DEPA-0.125 M TOPO diluted in kerosene. Density and surface 2 5 tension were found to follow simple negative linear relationship with temperature while an Arrhenius type model was adequate to fit the viscosity dependence on temperature.
Effect of anions in commercial phosphoric acid on the extraction of uranium by DEHPA /TOPO
Abstract Extraction of uranium from commercial phosphoric acid by DEHPA/TOPO process is a well-developed process on the commercial and pilot plant scale. Commercial phosphoric acid contains certain anions such as Cl−, F− and SO2− 4 in varying concentrations. The presence of such anions could have a negative effect on the extraction process. This paper investigated the effect of Cl−, F− and SO2− 4 anions present in commercial wet phosphoric acid on the uranium extraction process. The effect of adding SiO2 which complexes with F− and other anions was also studied. The results obtained showed that these anions formed complexes with UO2+ 2 and therefore had a negative influence on the extraction of uranium from laboratory and commercial phosphoric acids. This effect was strong in the case of F− followed by SO2− 4 and much less for Cl−. Addition of SiO2 was found to negate the effect of F− and other anions and to exert a positive effect on uranium extraction.
EFFECT OF OXIDATION-REDUCTION ON THE EXTRACTION OF URANIUM FROM WET PHOSPHORIC ACID BY DEHPA/TOPO
Uranium is recovered from wet phosphoric acid by DEHPA/TOPO in kerosene. Uranium is present in wet phosphoric acid in the tetravalent and hexavalent states but DEHPA/TOPO extracts uranium in the hexavalent state only. The ratio of U4+/U 6+ depends on several factors such as the origin of the phosphate rock, the method of preparation of phosphoric acid and the ~resence of other impurities. Therefore it is important to oxidize the wet acid to convert all uranium to U ~+ before extraction. Uranium is stripped from the solvent by a reverse process where a concentrated phosphoric acid is used under reducing conditions. This paper studies the oxidation of wet phosphoric acid from Homs plant/Syria by H202 oxidant and the effect of oxidation on extraction Coefficient K. It also studies the reduction by iron and its effect on back extraction of uranium from the solvent to phosphoric aci
The uranium(VI) extraction mechanism of D2EHPA-TOPO from a wet process phosphoric acid
Journal of Radioanalytical and Nuclear Chemistry - J RADIOANAL NUCL CHEM, 2002
This paper reports the results of an investigation into the solvent extraction of uranium from technical grade phosphoric acid using industrially available extractants as D2EHPA and TOPO diluted in technical grade kerosene. Preliminary tests showed that, the effect of different parameters such as uranium oxidation stage, temperature and the molar ratio of D2EHPA/TOPO on the uranium recovery was in good agreement with those of previous investigations. However, a detailed investigation into the effect of phosphoric acid concentration, organic concentration and acid/organic phase ratios suggested that the mechanism of D2EHPA/TOPO synergism was rather complex and it presented a different character depending on the acid concentration.