Recovery of uranium (VI) from water solutions by membrane extraction (original) (raw)
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Journal of Radioanalytical and Nuclear Chemistry, 2018
The suitability of dispersion liquid membranes (DLMs) to recover and purify uranium from simulated waste streams containing nitric acid, high uranium concentrations and radionuclide contaminants with tributyl phosphate (TBP) and ammonium carbonate ((NH 4) 2 CO 3) as stripping solution was investigated. The radionuclide surrogates were not extracted and complete uranium recovery was obtained from 15 g U L-1 solutions using a 1:4 ratio of 30% TBP in kerosene and 0.75 M (NH 4) 2 CO 3 dispersion. In addition, all the uranium in the stripping solution was precipitated. Consequently, DLM proved to be a promising solvent extraction contacting method for uranium recovery and purification.
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.
Application of Supported Liquid Membranes for Removal of Uranium from Groundwater
Separation Science and Technology, 1990
The separation of uranium from Hanford site groundwater was studied by hollow-fiber supported liquid membranes, SLM. The carrier bis(2,4,4-trimethylpentyl)phosphinic acid, H[DTMPep], contained in the commercial extractant Cyanex™ 272 was used as membrane carrier, because of its selectivity for U over calcium and magnesium. The water soluble complexing agent, 1-hydroxyethane-1,1-diphosphonic acid, HEDPA, was used as stripping agent. Polyproylene hollow-fibers and n-dodecane were used as polymeric support and diluent, respectively. Laboratory scale hollow-fiber modules were employed in a recycling mode, using as feed synthetic groundwater at pH 2, to confirm the capability of the proposed SLM system to separate and concentrate LJ(VI) in the strip solution, information was obtained on the U(VI) concentration factor and on the long-term performance of the SLMs. Encouraging results were obtained both with a conventional module and with a module containing a carrier solution reservoir. Industrial scale modules were used at Hanford to test the SLM separation of U(VI) from real contaminated groundwater. The uranium concentration was reduced from approximately 3,500 ppb to about 1 ppb in a few hours.
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.
Simultaneous extraction and stripping of uranium ions via multi-dropped liquid membrane system
Russian Journal of Applied Chemistry, 2015
An investigation on the separation of U(VI) from aqueous solutions via a multi dropped liquid membrane (MDLM) and its model is presented. A new method that is more advantageous than other liquid membrane techniques is applied. Di(2-ethylhexyl) phosphoric acid was used as a highly selective carrier for the transport of U(VI) ions through the MDLM. Maximum percentages of U(VI) extraction and stripping achieved were 98.9 % using 1.459 × 10-3 M D2EHPA as the extractant, 1 M NH 4 HCO 3 as the stripping solution. The infl uences of pH and temperature on donor and acceptor phases, the infl uence of carrier phase concentrations and membrane's fl ow velocity were investigated. For the description of relationships of U(VI) concentration in particular phases with time, a model based on the assumption of consecutive fi rst-order reactions was proposed. The kinetic parameters (k 1 , k 2 , R m max , t max , J d max , J a max) were calculated for the interface reactions assuming two consecutive, irreversible fi rst-order reactions. The activation energy value was calculated as 10.2 kcal mol −1 for extraction. The value of calculated activation energy indicates that the process is chemically controlled by U(VI) ions. The experiments have demonstrated that D2EHPA derivative is a good carrier for U(VI) transport through MDLM in the study.
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.
Desalination
Solvent extraction and facilitated transport of UO 2 2+ across supported liquid membrane containing N,N,N′,N′tetra-2-ethylhexyldiglycolamide (T2EHDGA) in n-dodecane as the carrier extractant and 30% iso-decanol as the phase modifier were investigated from nitric acid feed solutions. Extraction constants were comparable to those reported earlier for the U(VI)-TODGA extraction system at 3.0 M HNO 3 feed conditions and consequently, the transport rates were comparable with the two extractants. > 80% U transport was reported in 5 h while using 3 M HNO 3 as the feed and 0.01 M HNO 3 as the receiver phase solution. Mass transport modeling of the facilitated transport of uranyl ion across PTFE supported liquid membranes was done by a developed mathematical model. Diffusion coefficients were calculated using Danesi's model as well as by lag time measurements. The transport was found to be diffusion controlled in the membrane phase and the permeability coefficient was calculated to be (3.20 ± 0.13) × 10 − 4 cm/s for the feed composition of 3 M HNO 3 , receiver phase composition of 0.01 M HNO 3 and membrane carrier phase of 0.2 M T2EHDGA in n-dodecane containing 30% iso-decanol while the membrane diffusion coefficient was calculated to be (1.58 ± 0.16) × 10 − 6 cm 2 /s.
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.
Use of Membrane Emulsion Span 80 and Topo in Uranium Extraction and Stripping
Urania Jurnal Ilmiah Daur Bahan Bakar Nuklir
USE OF MEMBRANE EMULSION SPAN 80 AND TOPO IN URANIUM EXTRACTION AND STRIPPING. Membrane emulsion span 80 and TOPO used in uranium extraction and stripping has been done. The extraction was carried outby emulsion membrane H3PO4 in TOPO-Kerosene. The feed or external aqueous phase was uranium in HNO3. The emulgator span-80 was used to obtain a stable emulsion membrane system. The influence factors were percentage of TOPO-Kerosene, time extraction, molarity of external aqueous phase and molarity of internal aqueous. After the emulsion membrane was formed, the extractionand stripping process was performed. The ratio volume feed : volume membrane phase equal to 1 : 1 and volume of 5 % TOPO-Kerosene : Volume 3 M H3PO4 equal 1 : 1 were used. The relative good yield were obtained at concentration of TOPO in Kerosene and 3 M H3PO4 was 5 %, molarity of internal aqueous phase equal to 1 M, molarity of external aqueous phase 3 M H3PO4 and time extraction equalto 10 minutes with the speed of ...