Removal of radionuclides from low level radioactive liquid waste by precipitation

Six elements in several organs of mice fed with Zn deficient diet (Zn-def. mice) and those fed with control diet (control mice) were analyzed by INAA. Zinc concentrations in the organs of Zn-def. mice were not distinctly lower than those of control mice except for bone and pancreas. However, Ce content increased significantly in all organs of Zn-def. mice compared with control mice, indicating the partial substitution of Co with Zn in metal proteins or other materials for the Zn-def. mice.     

Removal of cobalt from liquid radioactive waste by in situ electrochemical synthesis of ferrite

This study combined electrochemical synthesis with traditional ferrite method to remove Co²⁺ from simulated liquid radioactive waste (LRW). The experiment investigated the effects of various reaction conditions including current density, reaction time for electrosynthesis, reaction temperature, initial pH value and boric acid concentration as well as the type of power supply by measuring the concentration of Co²⁺ in the effluent, explored the reaction mechanism by measuring particles using XRD. The results showed that it was feasible to remove Co²⁺ from simulated LRW by electrochemical synthesis of ferrite. The best removal efficiency of 99.99% (the concentration of Co²⁺ in the effluent was 0.447 μg/L) was achieved under the optimal reaction conditions, the sediment was mainly composed of the mixture of CoFe₂O₄ and Fe₃O₄.     

Separation of cesium from intermediate level liquid radioactive waste by solvent extraction with antioxidants

The intermediate level liquid radioactive wastes (RAW) isussed from nuclear power plants have high salt contents ca 200 g·dm^–3, the pH of liquid RAW being 12.5–13.7. A convenient method for separation of cesium under these conditions is solvent extraction with substituted phenols. For this purpose weere tested antioxidants produced in Czechoslovakia: AO 2246 [2,2-methylene-bis-(4-methyl-6-tertbutyl)phenol]; AO 4 [2-tertbutyl-4-(2-phenylpropyl)phenol]; AO 4K [2,6-ditertbuty-4-methylphenol]; AO 301 [2,2-methylene-bis-(4-{2-phenylpropyl}-6-tert-butyl)phenol]; and one antioxidant imporoted from Japan—NOCRAC 2246. This antioxidant is equivalent to AO 2246. After the first experiment it was found that the extraction efficiency for antioxidants AO 4 and Ao 301 is very low and the following experiments were made with AO 2246 (NOCRAC 2246) and AO 4K. Some effects on extracton as, pH of water phase, influence of diluent, influence of concentration of antioxidants, extraction time, were studied. The best results gave antioxidant NOCRAC 2246 in nitrobenzene, the extraction efficiency was 92.3% with pH 13.23.     

Removal of Thoron and Arsenazo III from radioactive liquid waste by sorption onto cetyltrimethylammonium-functionalized polyacrylonitrile

A surfactant-functionalized polyacrylonitrile (SFPAN) was synthesized in the present investigation via gamma radiation-induced polymerization and was applied for sorbing two hazardous organics, Thoron (TH) and Arsenazo III (ARIII), from radioactive liquid waste. Efficient removals were achieved for both organics over a wide range of pH. The sorption kinetic studies of TH and ARIII revealed that the equilibrium time is significantly dependent on the solution pH. Among the tested sorption kinetic models, the kinetic data of TH and ARIII fit well to the pseudo-second-order one. The sorption equilibrium data obtained for TH and ARIII were analyzed using Freundlich, Langmuir, Temkin and Dubinin–Radushkevich (D–R) isotherm models. The obtained results demonstrated that the equilibrium data are well described by Freundlich and D–R models. The calculated values of the sorption energy (E) and the Gibbs free energy change (ΔG ^o) suggested that the sorption process of TH and ARIII onto SFPAN is governed by physisorption. SFPAN was further tested for the uptake of the concerned organics from radioactive process wastewater. The obtained results suggest its applicability for the treatment of liquid organic radioactive wastes.     

Uranium determination in water samples by liquid scintillation counting after cloud point extraction

The aim of this study is the radiometric determination of uranium in waters by liquid scintillation counting (LSC) after pre-concentration of the element by cloud point extraction (CPE). For CPE, tributyl phosphate (TBP) is used as the complexing agent and (1,1,3,3-Tetramethylbutyl)phenyl-polyethylene glycol (Triton X-114) as the surfactant. The measurement is performed after phase separation by mixing of the surfactant phase with the liquid scintillation cocktail. The effect of experimental conditions such as pH, reactant ratio (e.g. m(TBP)/m(Triton), ionic strength (e.g. [NaCl]) and the presence of other chemical species (e.g. Ca²⁺ and Fe³⁺ ions as well as humic acid and silica colloids) on CPE has been investigated. According to the experimental results the total method efficiency is (13 ± 2)% and the chemical recovery (50 ± 10)% at pH 4 and reactant ratio (V(TBP)/V(Triton) = 0.1). Regarding the other parameters, generally Ca²⁺ and Fe³⁺ ions as well as the presence of colloidal species in solution (even at low concentrations) results in significant decrease of the chemical recovery of uranium. On the other hand increasing NaCl concentration leads to enhancement of chemical recovery. The detection limit under optimum experimental conditions has been found to be 0.5 Bq L^?1 indicating that the method could be applied only to waters samples with increased uranium concentration. Moreover, the negative effect of the chemical species found in natural waters limits the applicability of the method with the respect to environmental radioactivity measurements.     

Separation of phenols from aqueous micellar solutions by cloud point extraction

The cloud point technique was used to recover phenol, 4-methylphenol, and 4-nitrophenol from aqueous solutions using oxyethylated methyl dodecanoates as nonionic surfactants. Oxyethylated methyl dodecanoates are convenient nonionic surfactants for such separations. Their cloud points can be easily modified by a change in surfactant hydrophilicity or by the addition of a second nonionic surfactant and/or an electrolyte. The use of the hydrophile lipophile balance is preferred to model the cloud point of oxyethylated methyl dodecanoates and their mixtures with other surfactants. The composition of the surfactant-rich phase depends on electrolyte type and the overheating. The phase can contain only 5-15% of water. Recovery of phenols changes in the order 4-nitrophenol >4-methylphenol > phenol and is increased in the presence of sodium chloride. The presence of salting-out electrolytes is preferred both to decrease the cloud point and to increase the efficiency of extraction.     

Decontamination of oil-polluted soil by cloud point extraction

An extraction procedure based on cloud point phase separation of nonionic surfactants was used to remove oil contamination from soils. The detergent employed was Triton X-114, and its clouding behavior was monitored by means of a fluorescence probe. Changes in the I (1)I (3) ratio of pyrene indicated gradual dehydration of the detergent micelles upon heating. The rate of phase separation, and the volume and water content of the micellar phase were determined. In the practical clean-up, 85-98% of the oil present in the soil was found to enter the micellar phase of the separated washing liquid. A 15-min washing time with 3-5% detergent was found to be sufficient for this degree of contaminant removal from soil containing 0.009-0.017% oil, using a liquid:solid ratio of 5:2. The extraction efficiency decreased with increasing carbon content of the soil. The process holds promise for large-scale treatment of oil-polluted soils.     

Recovery of cesium from intermediate level liquid radioactive waste

The antioxidant Lowinox 22M46 (Naftonox 22M46) were used for the extraction of cesium from intermediate level liquid radioactive wastes.     

Concentration of radioactive components in liquid low-level radioactive waste by membrane distillation

The paper addresses some aspects of liquid low-level radioactive waste (LLLW) purification. Since the volume of liquid low-level wastes is usually large and the activity is rather low, the radioactive substances separated from the non-active portion have to be concentrated into the small volume for subsequent conditioning and disposal. The need for the improvement of decontamination and minimisation of the costs have led to new specific methods being under examination and development. The method proposed in the paper is membrane distillation. The experimental work described below supports the statement that membrane distillation can be an attractive alternative for liquid radioactive waste treatment. The advantages of membrane distillation over the other processes commonly used for the processing of LLLW are discussed in the paper.     

Determination of the isoflavone genistein in soybeans by high-performance liquid chromatography following cloud point extraction

A simple and sensitive method has been developed for preconcentration and determination of genistein in soybeans. This method is based on cloud point extraction (CPE) of genistein from soybeans using ethylene glycol monoalkyl ether (Genapol X-080) as a nonionic surfactant. The concentration of extracted genistein was determined by HPLC with a UV detector. Optimum experimental conditions were established. With 5% Genapol X-080 (v/v), a liquid/solid ratio of 25:1 mL/g, and ultrasonic-assisted extraction at 40 degrees C for 45 min, the extraction percentage of genistein reached its highest value. The preconcentration factor for genistein was about 16.5. The RSD for seven replicate measurements and the LOD were +/- 4.45% and 15.0 ng/mL, respectively. CPE is simple, inexpensive, and suitable for extraction of genistein from soybean. It uses environmentally friendly surfactants and offers a convenient alternative to more conventional extraction systems.     

Denitration of simulated radioactive liquid waste

Journal of Radioanalytical and Nuclear Chemistry - Radioactive liquid wastes containing large amounts of nitric acid (approx. 4–7 M) generated in the nuclear fuel cycle are very...     

Thorium determination in water samples by liquid scintillation counting after its separation by cloud point extraction

The aim of this study is the separation and pre-concentration of thorium from aqueous solutions by cloud point extraction (CPE) and its the radiometric determination by liquid scintillation counting (LSC). For CPE, tributyl phosphate (TBP) was used as the complexing agent and (1,1,3,3-Tetramethylbutyl)phenyl-polyethylene glycol (Triton X-114) as the surfactant. The radiometric measurements were performed after phase separation by mixing of the surfactant phase with the liquid scintillation cocktail. The effect of experimental conditions such as pH, ionic strength (e.g. [NaCl]) and the presence of other chemical species (e.g. Ca²⁺ and Fe³⁺ ions, and humic acid colloids) on the CPE separation recovery have been investigated at constant reactant ratio (m(TBP)/m(Triton) = 0.1). According to the experimental results the maximum chemical recovery is (60 ± 5)% at pH 3. Regarding the other parameters, generally Ca²⁺ and Fe³⁺ ions as well as the presence of colloidal species in solution (even at low concentrations) results in significant decrease of the chemical recovery of uranium. On the other hand increasing NaCl concentration leads to enhancement of chemical recovery. Generally, the method could be applied successfully for the radiometric determination of thorium in water solutions with relatively increased thorium content.     

Removal of60Co and134Cs from radioactive process waste water by flotation

The removal of¹³⁴Cs and⁶⁰Co from radioactive process waste water using cetyl pyridinium chloride (CPC) as a collector and cobalt(II) hexacyanoferrate(II) as a precipitant for⁶⁰Co and sorbent (ion exchanger) for¹³⁴Cs was intensively investigated and the best removal conditions could be established. The results indicate that under the optimum conditions removals higher than 96% and 97% could be achieved for Co(II) and Cs(I), respectively. Cobalt(II) hexacyanoferrate(II) was found to have high affinity for cesium and can preferentially remove it in presence of relatively high amounts of other alkali or alkaline earth cations. A two-stage flotation process was successfully tested for the removal of both Cs(I) and Co(II) from waters containing both cations.     

Analysis of 99Tc in the radioactive liquid waste after extraction into suitable solvent

⁹⁹Tc is one of the long lived fission product with high fission yield. From radioactive waste management point of view it is very much essential to evaluate the concentration of technetium in the radioactive liquid waste in order to finalise the treatment process to extract/isolate it from the stream which is discharged to the environment. For the estimation of ⁹⁹Tc in the radioactive liquid waste stream, extraction of the stable complex of technetium-tetraphenyl arsonium chloride (TPAC) into chloroform followed by beta counting was studied. Various parameters like pH, time of equilibration, concentration of TPAC in chloroform, use of other solvent for extraction as well as interference of various other radionuclides present in the waste were also studied. The radioactive liquid waste being handled in plant contains high concentrations of salts in the form of sodium nitrate. Hence effect of salt concentration on the percentage extraction was also evaluated. The extraction behavior does not dependent on change in the pH of the solution. Almost 99.5% extraction was observed in the pH range of 1?C13.0. High concentration of salt is affecting the extraction. However, this can be taken care by diluting the radioactive waste. It takes almost 90?min time for maximum extraction. Presence of radionuclides like ¹³⁷Cs, ⁹⁰Sr are not interfering the extraction of ⁹⁹Tc. However, ¹⁰⁶Ru is getting slightly extracted along with ⁹⁹Tc. The error due to ¹⁰⁶Ru can be eliminated by taking gamma spectrum and deducting the activity from the total beta activity to get ⁹⁹Tc activity. Nitrobenzene can be used for extraction of Tc?CTPAC complex in place of chloroform.     

Determination of thermodynamic parameters for cloud point extraction of Arsenazo-III and Magdala Red dyes using mixed micelles: An essential requirement for high performance

A simple and low cost method for extraction and preconcentration of Arsenazo-III (ARS-III) and Magdala Red (MR) was developed by an efficient cloud point extraction (CPE) method using mixed micelles of Triton X–114 (TX–114) and cetyltrimethyl ammonium bromide (CTAB). Various parameters, such as pH/concentration of H₂SO₄, surfactant concentrations (TX-114 and CTAB), equilibrium temperature and time have been studied to maximise efficiency. Thermodynamic quantities like change in Gibbs free energy (ΔG⁰), change in enthalpy (ΔH⁰) and change in entropy (ΔS⁰) were calculated. The results show that the CPE of ARS-III and MR dye is feasible, spontaneous, and endothermic in the temperature range of (50–80) °C indicating good recoveries for the developed method. The effect of temperature, surfactant concentration and dye concentration on various thermodynamic quantities was investigated and it was found that ΔG⁰ values increased with temperature but decreased with surfactant and dye concentration. ΔH⁰ and ΔS⁰ values increased as surfactant concentration increased and decreased as dye concentration decreased. The recoveries were found to be the range from 90.02 – 101.03 % for ARS-III and 86.07–99.46 % for MR dyes which proves that the method is highly efficient.     

Determination of triptonide by cloud point extraction combined with MEKC

A method has been developed for the determination of triptonide in the traditional Chinese herb Tripterygium wilfordii Hook F. by micellar electrokinetic capillary chromatography combined with cloud point extraction. The analyte was extracted at pH 3.0 by micelles of the nonionic surfactant polyoxyethylene 7,5-octylphenyl ether (Triton X-114). A 250-muL aliquot from the extracted surfactant-rich phase was diluted to 400 muL with ethanol to reduce its viscosity before separation by MEKC. Under optimum conditions, an enrichment factor of 25 is obtained and the determination limit of triptonide is found to be 3.15 x 10(-7) mol/L. The proposed method has been successfully applied to the determination of triptonide in T. wilfordii tablet and spiked urine matrix, demonstrating the feasibility and reliability of the proposed method.     

Recovery of molybdenum by solvent extraction from simulated high level liquid waste

Journal of Radioanalytical and Nuclear Chemistry - In this study, simple and a rapid solvent extraction method is investigated to recover Mo(VI) from simulated HLLW. The (NH4)6Mo7O24·4H2O...