Use of Membrane Emulsion Span 80 and Topo in Uranium Extraction and Stripping (original) (raw)
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Chemical Engineering and Processing - Process Intensification, 2018
Use of emulsion liquid membrane (ELM) extraction of uranium(VI) from lean streams containing nitric acid using tri-n-butyl phosphate (TBP) suffers from major drawback that TBP transports nitric acid to the strip phase, thereby reducing the driving force for extraction. This problem is completely eliminated by using near neutral sodium nitrate solution as the feed. The membrane phase is light liquid paraffin, containing TBP and the strip phase is aqueous sodium carbonate. Emulsion is stabilized using polymeric surfactant system, which exhibits low rate of leakage of the strip phase and no noticeable swelling of the emulsion. The key step is pH control of the continuous phase between 4.0 and 4.5 in order to neutralize sodium carbonate leaking from the emulsion phase. Effect of concentration of NaNO3 in the feed phase, Na2CO3 in the strip phase and volume ratio of the feed to the strip phase, on the rate of extraction of uranium(VI) and its enrichment, is studied. Using this process, it is possible to achieve nearly quantitative extraction of uranium(VI) with enrichment factor greater than 60. The superiority of the present process is established by comparing its performance with ELM extraction of uranium(VI) from nitric acid.
E3S Web of Conferences
The continuous extraction of uranium from artificial wastewater by an emulsion liquid membrane containing di-2-ethylhexylphosphoric acid (D2EHPA) and tri-n-butyl phosphate (TBP) as the carrier was carried out using one stage mixer-settler. The optimum condition gave the ratio of emulsion velocity to the feed velocity 1:4 and steady state reached after five minutes. The optimum condition was obtained at the 90.91 % of uranium recovered from raffinate, using EDTA as the masking agent with concentration 5x10-2M. The total concentration of carrier was 3% with ratio D2EHPA and TBP 3:1. The emulsion liquid membrane has high relative selectivity after steady state with separation factors were UNi 115.43 and UFe 328.55. The result of the experiment showed that emulsion liquid membrane containing D2EHPA and TBP as the carrier have good performance for the continuous system.
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.
Analytical Sciences, 1997
It was found that the extraction percent (L) values of U(VI), Th, Zr and Fe(III) from 0.1 mol dm-3 (M) HNO3 solution by 0.1 M TOPO in cyclohexane solution are 98, 78, 85 and 85%, respectively. Among these elements, only U(VI) and Th were found to be stripped from their organic phase by 0.1 M sodium citrate solution. Cerium, copper and cadmium were not extracted by trioctylphosphine oxide (TOPO) under similar conditions. Based on these equilibrium results, a liquid emulsion membrane (LEM) was prepared from TOPO/Span 80/sodium citrate and the factors affecting its stability were studied. Permeation of U(VI) into this membrane was kinetically studied in detail. Its forward permeation rate was found to be mainly dependent on TOPO concentration and slightly dependent on U(VI) and HNO3 concentration of the external phase. Permeation results showed that it is possible to recover 98% of U(VI) and 82% of Th from 0.1 M HNO3 solution containing Ce, Zr, Fe(III), Cd, and Cu by the membrane. The recovered U(VI) and Th were contaminated with less than 2% of Fe(III).
Recovery of uranium (VI) from water solutions by membrane extraction
The extraction of uranium from aqueous model solutions, as well as from real solutions reulting from leaching uranium ores was carried out in the system equipped with the Liqui-Cel® Extra-Flow membrane contactor with polypropylene capillary membranes. D2EHPA in toluene was used as an organic phase. Different arrangements of flow inside the membrane module were tested. The better approach appeared to be the arrangement with aqueous phase in the shell side of the contactor and organic phase inside the capillary membrane. The extraction efficiency for model solutions reached 95% and 87% for real post-leaching liquors.
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.
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.
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.
Using microemulsion for recovery of uranium from phosphoric acid of Annaba (Algeria)
Hydrometallurgy, 2004
In this work the microemulsion liquid membrane operation of reversed type water-in-oil was applied to extraction of uranium from phosphoric acid produced at Annaba plant in Algeria. Obtained results show that an extraction yield of more than 90% of uranium present in the phosphoric acid may be reached in three theoretical stages with aqueous/organic phase ratio = 12:1 without acid pretreatment for the removal of organic matter. The extracted uranium was precipitated and the microemulsion was recycled for further use as solvent phase. D