ION EXCHANGE BEHAVIOR OF ZEOLITES A AND P SYNTHESIZED BY NATURAL CLINOPTILOLITE (original) (raw)
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Environ Geochem Health , 2022
investigations, activity concentrations of gammaemitting radioactive elements discovered in soils are higher than the global average crustal values, especially around mining activities. Adsorption technique is the most prevalent remedial method for decontaminating radiochemically polluted sites. However, there is a need to investigate integrated approaches/combination techniques. Although complete radionuclide decontamination utilizing the various technologies is feasible, future research should focus on cost-effectiveness, waste minimization, sustainability, and rapid radionuclide decontamination. Radioactive materials can be harnessed as fuel for nuclear power generation Abstract Several anthropogenic activities produce radioactive materials into the environment. According to reports, exposure to high concentrations of radioactive elements such as potassium (40 K), uranium (238 U and 235 U), and thorium (232 Th) poses serious health concerns. The scarcity of reviews addressing the occurrence/sources, distribution, and remedial solutions of radioactive contamination in the ecosystems has fueled data collection for this bibliometric survey. In rivers and potable water, reports show that several parts of Europe and Asia have recorded radionuclide concentrations much higher than the permissible level of 1 Bq/L. According to various
2003
Appreciable concentrations of natural uranium and its daughter radionuclides may occur in drinking water obtained from drilled wells when the bedrock contains these nuclides. Effective methods are needed to remove these radionuclides. A wide range of ion exchange materials, both organic and inorganic, were evaluated for the removal of 234,238 U, 226 Ra, 210 Po and 210 Pb from ground waters. Screening tests were carried out, in which distribution coefficients (K D) were determined for the ion exchangers. The ion exchangers that gave the highest K D 's were tested in column-mode experiments for the removal of the radionuclides from drilled well water. The most efficient exchanger for the removal of U from neutral and slightly alkaline waters was the strong base anion resin. The chelating aminophosphonate resin removed uranium very efficiently from slightly acidic water. As well, it was an efficient exchanger for the removal of toxic and harmful transition metals from drilled well waters. The strong and weak acid cation resins and zeolite A removed radium most efficiently. Large fractions of the total activity of polonium and lead were found to adsorb on equipment in the ion exchange studies. In investigation of this, the well waters were filtered through membranes to determine the soluble and particle-bound forms of 234,238 U, 226 Ra, 210 Po and 210 Pb. Eight of the waters were of Ca−HCO 3 type and two were of Na−Cl type. Some of the waters also had high concentrations of Fe, Mn and humic substances. Uranium was present entirely in soluble form, probably as uranyl ion in soluble carbonate complexes. 226 Ra was in soluble form in the waters with low concentrations of Fe and Mn, but 10% of the total radium activity was bound to particles in Fe−Mn-rich waters. The speciation of Po is complex in natural waters; polonium was present in both soluble and particle-bound forms. A correlation was observed between the fractions of particle-bound 210 Po and the concentrations of iron in the raw waters. A considerable amount of the total activity of 210 Pb was found in the coarse particle fraction in iron-bearing water. The results of the study show ion exchange to be an effective method for the removal of uranium and radium from drinking water. Efficient removal of polonium and lead will often require a second purification method. vi CONTENTS ABSTRACT i PREFACE AND ACKNOWLEDGEMENTS ii LIST OF PUBLICATIONS iv ABBREVIATIONS v vii 5. RESULTS AND DISCUSSION 5.1 Removal of 234,238 U, 226 Ra, 210 Po and 210 Pb by Ion Exchange Method 5.1.1 Screening of the ion exchangers 37 5.1.2 Column experiments 39 5.2 Physico-Chemical Forms of U, 226 Ra, 210 Po and 210 Pb and Their Influence on Ion Exchange 5.2.1 Effects of pH and U concentration on the removal of uranium 5.2.2 Adsorption on the filtration system and filters 47 5.2.3 Fractions of radionuclides in soluble form 48 5.2.4 Radionuclides in particle-size fractions 5.3 Removal of Metals and Anions from Ground Waters by Ion Exchange 6. CONCLUSIONS REFERENCES
Uranium Remediation by Ion Exchange and Sorption Methods: A Critical Review
Johnson Matthey Technology Review, 2016
The solid phase materials or sorbents applied to the removal of uranium from industrial waste streams and surface waters are reviewed. The speciation of the element in the environment is discussed. A series of examples on uranium remediation from the recent literature using the different kinds of solid phase sorbents are reviewed in detail and evaluated. The criteria for making the best choice of ion exchanger are discussed with suggestions for further evaluation of the described technologies.
Removal of Uranium from Mine Water Using Ion Exchange at Driefontein Mine
2009
Mine waters from gold and sometimes coal mining contain low but potentially harmful levels of uranium. These are not easily removed by conventional treatment technologies such as lime precipitation. The use of ion exchange resins for the recovery of uranium from water sources in especially mine water circuits is commonplace and can be considered to be state-of-the-art for medium to low uranium concentrations. A pilot plant was operated at Driefontein mine to determine the ability of ion exchangers (Lewatit Monoplus S6368) to reduce low levels of uranium to below acceptable International Discharge Limits. Results show that uranium can be reduced to below 10 µg/l consistently, and that the uranium can be effectively eluted from the ion exchange resin. The selected resin showed a very high affinity for uranium, resulting in very long run times and hence giving extremely low operating costs. Data has been obtained for engineering design purposes, and has exposed the particular challenge...
Removal of radionuclides from Estonian groundwater using aeration, oxidation, and filtration
Proceedings of the Estonian Academy of Sciences, 2012
Groundwater in the northeastern suburb of Tallinn was analysed to determine the content of iron, manganese, sulphides, ammonia, and radionuclides (Ra 226 , Ra 228) and total radioactivity. It was established that for several wells of the Cambrian-Vendian water layer the annual effective dose would exceed the EU guideline for drinking water (0.1 mSv/yr). The purpose was to find a technology for simultaneous purification of groundwater from iron, manganese, sulphides, ammonia, and some radionuclides (Ra 226 , Ra 228). A pilot plant consisting of a Venturi-type aeration unit GDT (Gas-Degas Technology, Mazzei Corp., USA), an oxidation tank, and two-stage filtration columns was constructed. Several non-catalytic (Everzit Special Plus, sand) and catalytic filter materials (Filtersorb FMH, Pyrolox) were tested. Along the flow sheet from the aerator to the II stage filter outlet the pH, dissolved oxygen and carbon dioxide, turbidity, the content of iron, manganese, and ammonia were monitored, mainly by using spectrophotometry (HACH DR/2000). Radioactivity of water samples was determined by the Estonian Radiation Centre using the liquid scintillation counting method and γ-spectrometry. It was established that by intensive aeration of groundwater followed by oxidation for a certain contact time and appropriate selection of filter materials of different properties, it was possible to remove together with iron and manganese also radium isotopes. The total effectiveness of the process was 90% removal of gross-alfa and 70% removal of gross-beta activity of groundwater. Since the uranium content in the well water was marginal and radon was almost totally (99%) removed in the degas separator, the total effective dose was calculated by Ra 226 and Ra 228. It was about 0.067 mSv/yr, which is lower than the EU DWD guideline (0.1 mSv/yr). The theoretical assumption that radionuclides were already removed with Fe(OH) 3 flocks in the first filtration step was verified by examining wash water. The radioactivity of wash water containing precipitate and the filtered wash water were measured. Results showed 4.6 times higher gross-alfa and 5.3 times higher gross-beta activity in the water containing precipitate. The co-precipitation process, where MnO 2 and Fe(OH) 3 flocks played an essential role, resulted in simultaneous removal of radium isotopes. Co-precipitation of radium with MnO 2 was more effective than with Fe(OH) 3 .
Natural and anthropogenic radionuclides in water and wastewater: Sources, treatments and recoveries
Journal of Environmental Radioactivity, 2020
Water-energy nexus in the context of changing climate amplifies the importance of comprehending the transport, fate and recovery of radioisotope. While countries have been more interested for zero/low greenhouse gas emission technologies, energy production from nuclear power plant (NPP) can be a prominent solution. Moreover, radioisotopes are also used for other benefits such as in medical science, industrial activities and many more. These radionuclides are blended accidently or intentionally with water or wastewater because of inefficacious management of the nuclear waste; and therefore, it is an imperative task to manage nuclear waste so that the harmful consequences of the waste on environment, ecology and human health can be dispelled. Due to generation of significant amount of waste throughout its utilization, a noticeable number of physical, chemical and biological processes has been introduced as remediation processes although mechanisms of optimum removal process are still under investigation. Removal mechanisms and influencing factors for radionuclide removal are elucidated in this review so that, further, operation and process development can be promoted. Again, resource recovery, opportunities and challenges are also discussed for elevating the removal rates and minimizing the knowledge gaps existing in development and applications of novel decontamination processes.
Uranium recovery from industrial effluent by ion exchange—column experiments
Minerals Engineering, 2005
The recovery of uranium from nuclear industrial effluent has been studied using laboratory column and polymeric ion exchange resin. The industrial effluent, at pH around 10, contains uranium (40 mg/L), ammonium (80 g/L) and carbonate (170 g/L) and cannot be discharged without previous treatment. Uranium is in the form of uranyl quadrivalent complex anions [UO 2 (CO 3) 3 ] 4À. The resin IRA 910 U was employed for its specific application for uranium extraction. Adsorption was carried out at flow rate of 1.0, 2.0, and 5.0 mL/min, which corresponds to a retention time of 10, 5.0 and 2.5 min, respectively. The use of ion the exchange technique makes the recovery of more than 98% of the uranium possible. Elution was carried out with ammonium carbonate solutions and also with the diluted effluent. The eluate contained uranium ranging from 2.4 to 2.7 g/L. The solution eluate might be recycled back into the process with the advantage of saving this valuable metal.
Applied Radiation and Isotopes, 1999
Five samples of natural zeolites from different parts of Iran were chosen for this study. In order to characterize and determine their structures, X-ray diffraction and infrared spectrometry were carried out for each sample. The selective absorption properties of each zeolite were found by calculating the distribution coefficient (K d) of various simulated wastes which were prepared by spiking the radionuclides with 131 I, 99 Mo, 153 Sm, 140 La and 147 Nd. All the zeolite samples used in this study had extremely high absorption value towards 140 La; clinoptolite from Mianeh and analsite from Ghalehkhargoshi showed good absorption for 147 Nd; clinoptolite from Semnan and clinoptolite from Firozkoh showed high absorption for 153 Sm; mesolite from Arababad Tabas showed good absorption for 99 Mo; and finally mesolite from Arababad Tabas, clinoptolite from Semnan and clinoptolite from Firozkoh could be used to selectively absorb 131 I from the stimulated waste which was prepared. The natural zeolites chosen for these studies show a similar pattern to those synthetic ion exchangers in the literature and in some cases an extremely high selectivity towards certain radioactive elements. Hence the binary separation of radioactive elements could easily be carried out. Furthermore, these zeolites, which are naturally occurring ion exchangers, are viable economically and extremely useful alternatives in this industry.
Ion-exchange separation of uranium, thorium and plutonium isotopes from environmental samples
Journal of Radioanalytical and Nuclear Chemistry Articles, 1996
Radioisotopes of uranium, thorium and plutonium in water, soil and fertilizer samples, have been chemically separated and determined by alpha-spectrometry method. Radiochemical procedure involving ion-exchange, enabled to determine these isotopes in very low concentrations (under 50 IJ-Bq/g). 232U, 229Th and 238Pu were used as a tracers for radiochemical yield recoveries (up to 90%). Thin layer so~ces have been obtained by electredeposition.