Feasibility Study on the Separation of Uranium and Thorium by a Hollow Fiber Supported Liquid Membrane and Mass Transfer Modeling (original) (raw)
Related papers
Journal of the Chinese Institute of Chemical Engineers, 2007
Extraction and stripping of uranium ions from nitrate media using a hollow fiber liquid membrane contactor was studied. In this study, tri-butyl phosphate (TBP) diluted in kerosene was used as extractant and sodium hydroxide was applied as a stripping solution. Uranium ions were extracted using TBP 5%(v/v) by rejecting thorium ions into raffinate with a maximum percentage of extraction for the uranium being 67%. The mathematical model was focused on the extraction side of the liquid membrane system. The permeability for each concentration of HNO 3 was investigated by mass transfer theory. When the concentration of HNO 3 increased, more uranium ions were extracted; however, when the concentration of uranium and thorium in the feed solution was increased, the percentage of extraction and stripping slightly decreased because the permeability decreases when the concentration of the feed solution increases due to membrane fouling and concentration polarization.
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.
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.
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.
Journal of Radioanalytical and Nuclear Chemistry, 2018
In this study the application of various surfactant agents on the performance of HFRLM for uranium transfer was investigated. Using Taguchi experimental design in recycling mode of HFRLM, maximum uranium recovery of 63.17% was obtained at 0.15 mol L-1 H 2 SO 4 , 0.0125 mol L-1 Alamine 336 and 0.25 mol L-1 NH 4 Cl in the donor, liquid membrane and acceptor phase, respectively. Also, the continuous mode experiments were conducted and HFRLM stability was compared with HFSLM. The uranium transfer would be improved by adding 0.
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.
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).
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.
Desalination, 2008
Membrane based non-dispersive solvent extraction (NDSX) of Th(IV) from aqueous nitric acid medium was carried out using din -hexyl octanamide (DHOA) in normal paraffin hydrocarbon (NPH) using a commercial hollow fiber module containing microporous hydrophobic polypropylene capillaries. The NDSX operation was carried out with pumping various concentrations of nitric acid (1-6 M) containing Th(IV) through the tube side and organic extractant (usually 1.1 M DHOA in NPH) through the shell side of the hollow fibre capillaries at aqueous and organic phase flow rates of 3.5 mL/s and 4.5 mL/s, respectively. Extraction studies were performed under different hydrodynamic conditions and the overall mass transfer was evaluated under counter-current flow condition. The percentage NDSX of Th(IV) increased with the increase in the extractant concentration (from 0.1 M DHOA to 1.1 M DHOA) as well as with nitric acid concentration (from 1 M to 6 M). Stripping studies were carried out using both distilled water as well as oxalic acid as the strippant. The possibility of the separation of U from Th was also evaluated.