Precipitation of uranium from low-level liquid wastes

A method for the recovery of uranium from low-level liquid wastes is described. Uranium(VI) is reduced to uranium(IV) in sulphuric-phosphoric acid solution with iron(II). The uranium(IV) is precipitated as the double duoride with sodium. The uranium content of the filtrate is in the low ppm range. Possible modifications to the procedure are discussed.     

Porous nanofiber membrane from phase separation electronspun for selectively recovering uranium from seawater

Journal of Radioanalytical and Nuclear Chemistry - Polymer fibers with amidoxime group are promising candidates to extract uranium from seawater. However, their application is limited majorly by...     

Studies on sorption of uranium on chitin: a solid-state extractant application for removal of uranium from ground water

Studies were carried out to remove uranium from aqueous systems based on the solid phase extraction of uranium by powdered chitin. The effects of various parameters like pH, contact time, and amount of chitin for quantitative sorption of uranium on chitin have been studied. The sorption studies with spiked water samples and natural ground water samples showed that uranium was easily sorbed onto powdered chitin between pH 3 and 6. The effects of various cations and anions, which are present in the water samples, were studied. The method is simple, fast and environmental friendly and it is unaffected by the other ions present in the natural waters. The accuracy of the method was evaluated by applying the present method on ground water samples containing uranium in the range of 100–2,200 μg/L. The uranium remained in water samples is <20 μg/L after treatment with chitin, which is below the AERB limits given for uranium in drinking water. The values are an average of five replicate measurements, with an RSD of ±10 μg/L at 100 μg/L uranium in water samples.     

Studies on recovery of uranium from fluoride matrix employing sonochemistry

Application of power ultrasound in chemical processes is recognized as an effective tool to solve many industrial problems encountered in processes involved in nuclear industry, particularly, digestion and leaching steps. In addition, problems related to radiological safety are the most important factors to be considered, when handling radioactive materials. Sonochemical processes, due to relatively low temperature operations, are attractive in this regards. Further they are eco-friendly and economical as well. Hence, sonochemical studies were taken up for the removal of uranium from fluoride containing matrix. Dissolution studies were carried out in nitric acid medium, in a 5 L capacity tank type sono-reactor, operating at frequency and power of 22 ± 3 kHz and 150 W respectively. The parameters studied were concentration of HNO₃, temperature of water-bath, choice of purged gas (air/oxygen) and flow rate of purged gas passed. Experiments were also carried out to study the amount of fluoride matrix dissolved. Enhancement with US was 76 to 91 % for U removal from MgF₂ slag in 2 M HNO₃. The prime advantage achieved is the reduction in the reaction time. Other advantages are minimizing labor, remotisation of operations to reduce radiation exposure, use of less acid and accordingly lesser effluent for treatment before disposal.     

Production potential of medical isotopes from natural uranium fission processes

Journal of Radioanalytical and Nuclear Chemistry - We present the results of gamma ray yield measurements from the neutron induced fission of natural uranium at a low power research reactor. Our...     

Chromatographic isolation of144Ce and144Pr from the wastes of irradiated uranium treatment

A two-step chromatographic technique was elaborated to isolate¹⁴⁴Ce,¹⁴⁴Pr from a solution of uranium fission products in 6M HNO₃. The oxidation to Ce(III) by bromate and selective adsorption of¹⁴⁴Ce(IV) on anion exchange column were used to concentrate and purify¹⁴⁴Ce. Some impurities of uranium,⁹⁵Zr,⁹⁵Nb,¹⁰⁶Ru remain in¹⁴⁴Ce solution after the first step of its isolation. The final purification is achieved by passing the 6M HNO₃ solution of¹⁴⁴Ce(IV) through the HDEHP-coated teflon column. The decontamination factors of¹⁴⁴Ce from main fission products are given. 7.2 mCi of (¹⁴⁴Ce+¹⁴⁴Pr) are recovered from each gram of irradiated uranium trioxide with the yield greater than 99%. An improvement of known generator was carried out to elute a purer¹⁴⁴Pr from maternal¹⁴⁴Ce(IV) adsorbed on the anion exchange column.     

Distribution of uranium in sediment of creek ecosystem

The present study was carried on distribution of uranium isotopes and Thorium in marine sediment from creek of Mumbai Harbour Bay (MHB) using radiochemical separation followed by alpha spectrometry. The activity concentration of uranium and thorium in sediment of MHB has ranged between 1–4 and 1.8–4.5 ppm respectively. The activity ratio of ²³⁴U/²³⁸U in sediment was found close to unity at most of the locations of creek suggesting a conservative behaviour. The observed Th/U ratio (0.9) in comparison to global Th/U ratio (?3.5) in the creek sediment indicates that it receives low radiogenic nature of terronenous input.     

The transfer of uranium from sediment to water along Jucar River, Spain

The effect of sediment size, pH, temperature and conductivity on the transfer of uranium from sediment to water has been studied. The uranium concentration and the²³⁴U/²³⁸U,²³⁵U/²³⁸U activity ratios were measured in water, sediments and suspended matter sampled from Jucar River, using low level alpha-spectrometry. Distribution factors were obtained from these measurements. A more detailed sampling was done in the neighbourhood of the Cofrentes Nuclear Plant (Valencia, Spain). Total uranium activity,²³⁴U/²³⁸U activity ratio and distribution factors for²³⁴U and²³⁸U were found to vary with pH. Leaching and dilution, which depend on pH and salinity, are the probable mechanisms for these changes.     

Liquid membranes for separating uranium from vanadium and uranium from molybdenum

This is the third paper in which we describe the transport of uranium ions through liquid membranes. The subject of this paper is the use of liquid membranes to separate uranium from other metals that are present in hydrometallurgical leach solutions derived from uranium ores. It is demonstrated that liquid membranes can cleanly separate uranium from vanadium. The separation of uranium and molybdenum is also investigated. Although this separation is not as clean as that of uranium and vanadium, the results indicate that further refinement of operating conditions of the liquid membrane could lead to substantial improvement. Based on the potential of the membranes to separate the various metal ions, several process schemes are suggested that could be used to recover uranium from hydrometallurgical leach solutions     

Electrode processes of uranium ions and electrodeposition of uranium in molten LiCl-KCl

In the first part, LiCl-KCl-UCl₃ and LiCl-KCl-UCl₃-UCl₄ molten salts were prepared, which were studied employing cyclic voltammetry and chronopotentiometry techniques, respectively. It was determined that the reduction of U(IV) to uranium metal takes two steps. Firstly, U(IV) is reduced to U(III). Then, the reduction of U(III) to uranium metal occurs in a step with a global exchange of three electrons. Cyclic voltammetry studies indicated that at low sweep rates, the reduction of U(III) to uranium is reversible. However, a mixed control of both diffusion and electrontransfer is observed as the sweep rate increases. The diffusion coefficient of U(III) and the formal potential of U(III)/U versus Ag/AgCl reference electrode in these two salt systems were calculated respectively. In second part, based on the data of the electrode processes of uranium ions, electrodeposition of uranium metal was carried out. Uranium deposits were prepared adopting a 304 stainless steel electrode in the molten LiCl-KCl-UCl₃ and LiCl-KCl-UCl₃-UCl₄, respectively by employing suitable electrolytic techniques. The morphology of the deposits and the cross-section of the cathode were investigated by SEM. It was determined that at the beginning of the deposition process, uranium product alloys with stainless steel and forms a thin layer, and then uranium begins to grow adhering to the layer.     

Determination of uranium in pore water from coastal sediment by standard addition ICP-MS analysis

Mass spectrometry using ICP-MS was applied to determine the uranium content in pore water samples through the standard addition method. This method requires less than 0.2 ml of a water sample, without any chemical separation. The sample solution (50 mg) was diluted with ∼1% HNO₃ to make a total weight of 5.00 g, after the addition of uranium standard. The method introduced 1% of analytical precision for measured uranium in the samples. This rapid and simple technique allows multi-trace elemental quantification using mixed standards. The behavior of uranium in pore water and the variations of uranium content at different depths of pore water are discussed.     

Application of modified wastes from phenol-formaldehyde resin and expanded polystyrene in sewage treatment processes

A solution to environmental pollution by polymer plastic wastes can be their chemical modification in to useful products. Such a new solution is the obtaining of effective flocculants for sewage treatment from chemically modified phenol-formaldehyde resin production wastes (SE and NS novolak) and expanded polystyrene wastes. Comparative analysis of flocculation properties was performed for amino derivatives of novolak wastes, synthesized sulphonated derivatives of novolak and expanded polystyrene wastes, of standard polyacryloamide and for Praestol commercial polyelectrolyte. Amino derivatives and sulphonated derivatives of polymer plastic wastes, having properties of anionic type polyelectrolytes, exhibit good flocculation properties in purification processes of sewages with a chemical composition close to that of found in the water circulating system power plant, coal-mine, and steel plant. Application of synthesised flocculants caused a decrease of turbidity, concentration of solved impurities and improved quality parameter of purified water. It was found that synthesised polyelectrolytes could be used in industrial water treatment processes.     

Electrode materials derived from plastic wastes and other industrial wastes for supercapacitors

The present review not only devotes on the environmental consequences of plastic bag wastes and other industrial wastes observable in the landfills,in the oceans or elsewhere but also gives a new insight idea on conversion of them into worth material,carbon,for the best electrochemical supercapacitor.Transformation of plastic wastes into high-value materials is the incentive for plastic recycling,end-oflife handling case for plastic bag wastes in practice quite limited.The plastic recycling waste for reuse saves energy compared with manufacturing virgin materials.Herein,we identified several synthetic methods to convert plastic waste and other industrial wastes into carbon material for supercapacitor.Different kinds of carbon materials,including nanofiber,nanotube,graphene,mesoporous carbon,etc.,have been derived from plastic waste,and thus give a superior potential for transforming trash into a "gold capacitor".Finally,conclusions and future trends of high-voltage supercapacitors were made as well as the easy and mass production of high-performance electrode materials for supercapacitors.Our work offers a promising sustainable approach to handle plastic bags,waste,and other industrial wastes and provides a new avenue in supercapacitor applications and other areas.     

Studies on sorption of antimony and europium from liquid organic and aqueous radioactive wastes on different sorbents

Sorption of¹²⁴Sb(III) from benzene, toluene, o-xylene and nitrobenzene on treated fly ash, pyrolysis residue and bentonite clay was studied at room temperature using the batch method. In comparison to a former study for the sorption of¹²⁴Sb(V), the results revealed relatively higher sorption of the trivalent state than the pentavalent one. According to the type of the nonpolar solvent used, the order of uptake of the radioactive isotopes was often o-xylenetoluene>benzene. The sorption tendency of the sorbents used towards the radionuclides was: bentonitepyrolysis residue>treated fly ash. Sorption from an aqueous medium on the same sorbents has also been investigated for¹²⁴Sb(III) compared to¹²⁴Sb(V),¹⁵²Eu(III) and their mixtures. The obtained results showed that the order of uptake of the different radionuclides was: Eu(III)>>Sb(III)>Sb(V)>mixture. The investigation was extended to the desorption studies of these radionuclides in the acidic and the neutral media from the dried radioactivity loaded sorbents.     

X-ray and electron induced Auger processes for I2 adsorption on uranium

The accurate determination of the kinetic energy of X-ray induced Auger electrons, which is necessary in XPS experiments, e.g. for calculating the Auger parameter, is sometimes hampered by peak interferences or by the high secondary electron background. The latter is of special importance for low kinetic energy electrons like e.g. the U(OPV) and U(OVV) Auger electrons. These problems can be circumvented by using electron induced Auger transitions (AES). However, since XPS and AES use different reference points for the energy scales, both scales have to be matched. This can be done by measuring the kinetic energy of an appropriate Auger transition in XPS and relating this value to the maximum of the second derivative of the same peak in AES.     

Studies of leaching of copper ores and flotation wastes

In Poland, there are significant deposits of copper ores. During the copper extraction, large amounts of flotation wastes are produced. In the ores and flotation wastes many other important elements are present. The main goal of this work was analysis of uranium content and to elaborate procedures for recovery of U from these materials. Two types of ores and four types of waste were examined. It has been found that uranium content varies from 4.5 to 25 ppm. The other elements have also been determined in these materials: Cu (4–5 % in ores and 0.3–1.7 % in waste), Ag, Re, Mo, La, Ni, V, etc. For leaching, sulfuric acid and sodium carbonates of various concentrations (temperature, time) were used. The optimum conditions for leaching have been found. The concentration of uranium in the final solution was generally less than 25 μg/mL. The other elements are also present in the leaching solutions. Simultaneous liquid–liquid extraction of uranium with these elements from leaching solution is under study. In our opinion, only such combined procedure for the recovery of uranium together with the accompanying elements could be cost-effective.     

Molecular distillation process for recovering biodiesel and carotenoids from palm oil

Carotenoids and biodiesel from palm oil were recovered through a process involving neutralization and transesterification of palm oil followed by molecular distillation of the esters. The concentrated obtained contains more than 30,000 ppm of carotenoids and the distillate contains above 95% of light-colored biodiesel. The experimental data were obtained from falling film and centrifugal molecular distillators. It can be seen that each one has its own characteristics, which are a function of the operating temperatures and of the tendency of the material thermal decomposition. These characteristics can determine the type of equipment to be used, since they have different operating conditions. The experimental results were compared to the ones from simulations using the mathematical modeling for the falling film and centrifugal distillators developed.     

Separation of uranium from soils for its determination

A method has been developed for the determination of microamounts of uranium in soils, which is based on application of the rapid and effective removing of luminescence quenchers from liquid preparations with subsequent uranium determination by laser-induced luminescence registration of its polysilicate complexes. To remove the luminescence quenchers, they were precipitated in strongly basic carbonate medium in the presence of activated charcoal (as a collector of the precipitate).