Airi Paajanen

Efficient removal of cesium from low-level radioactive liquid waste using natural and impregnated zeolite minerals

The objective of the proposed work was focused to provide promising solid-phase materials that combine relatively inexpensive and high removal capacity of some radionuclides from low-level radioactive liquid waste (LLRLW). Four various zeolite minerals including natural clinoptilolite (NaNCl), natural chabazite (NaNCh), natural mordenite (NaNM) and synthetic mordenite (NaSM) were investigated. The effective key parameters on the sorption behavior of cesium (Cs-134) were investigated using batch equilibrium technique with respect to the waste solution pH, contacting time, potassium ion concentration, waste solution volume/sorbent weight ratio and Cs ion concentration. The obtained results revealed that natural chabazite (NaNCh) has the higher distribution coefficients and capacity towards Cs ion rather than the other investigated zeolite materials. Furthermore, novel impregnated zeolite material (ISM) was prepared by loading Calix [4] arene bis(-2,3 naphtho-crown-6) onto synthetic mordenite to combine the high removal uptake of the mordenite with the high selectivity of Calix [4] arene towards Cs radionuclide. Comparing the obtained results for both NaSM and the impregnated synthetic mordenite (ISM-25), it could be observed that the impregnation process leads to high improvement in the distribution coefficients of Cs+ ion (from 0.52 to 27.63 L/g). The final objective in all cases was aimed at determining feasible and economically reliable solution to the management of LLRLW specifically for the problems related to the low decontamination factor and the effective recovery of monovalent cesium ion.

Removal of Radioactive Cesium from Nuclear Waste Solutions with the Transition Metal Hexacyanoferrate Ion Exchanger CsTreat

Abstract A transition metal hexacyanoferrate product CsTreat has been utilized at industrial scale for radioactive cesium separation at several nuclear power plants (NPPs) in several countries. A granular hexacyanoferrate ion exchanger has been used in packed-bed column mode operations for the removal of cesium from a variety of wastewater types. CsTreat beds have successfully purified both high-salt evaporator concentrates and dilute floor drain waters at NPPs in Finland and the United States. Furthermore, medium-active reprocessing solutions, containing high concentrations of sodium nitrate, have been decontaminated by a CsTreat bed at the Japan Atomic Energy Research Institute. These solutions are described as are other industrial applications of this ion exchange material, which, of all the commercial materials, has been shown to be the most selective exchanger for cesium. In addition, some prospective fields of hexacyanoferrate utilization, such as the use of CsTreat powder in a precoat filtration system, are discussed.

Hydrolysis and H+/Na+ exchange by Chelex 100 chelating resin

Abstract Chelex 100 chelating resin, as supplied (mixed sodium/hydrogen form 43% /57%), was found to be readily hydrolyzable through hydronium ion exchange from water. Contact with deionized water in solution volume to exchanger weight ratios of 10–4000 brought sodium ions into solution with concentrations of 0.05–1.5 mM and increased the pH from 6.1 to 8.7–10.0. In addition to sodium and hydroxide, the exchanger was found to release chloride and carbonate ions. The two acetate groups vary substantially in their selectivities to hydronium ions, the corrected selectivity coefficients being 1.3 × 10 9 and 1.4 × 10 3 , respectively.

Advanced separation of harmful metals from industrial waste effluents by ion exchange

Advanced separation methods of harmful metals from industrial waste effluents, i.e., radionuclides from nuclear waste solutions, transition metals from metallurgical waste effluents, developed at the Laboratory of Radiochemistry, are discussed.

Separation of Europium from Cobalt Using Antimony Silicates in Sulfate Acidic Media

The ores of rare earth elements (REEs) are usually digested in concentrated sulfuric acid media, which dissolve the REEs as main product with heavy metals as byproduct. In the present work, inorganic ion exchangers based on silico-antimonates (SiSb) were synthesized and characterized. SiSb mixed with metal oxides were prepared in molar ratio 2:1 with different aging time. In batch experiments, radionuclides Eu-152 and Co-57 were taken to represent the lanthanides and heavy metals, respectively. The sorption behavior was examined and distribution coefficients were evaluated for different effective conditions such as sulfuric acid concentration, pH, shaking time, metal ion concentration, and aging time. The new inorganic SiSb materials are characterized by rapid kinetics for Eu(III) and high adsorption selectivity for Co(II). The results showed that the SiSb are acidic in character and that their cation-exchange properties are better in low acidic media. Sorption efficiency is highly correlated with the structural framework, which depends on exchangeable water content. Various chelating agents were tested for desorption of the retained Eu(III) and Co(II). Maximum separation factors were obtained with SiSb materials after 2 or 3 days aging, providing efficient exchangers for the separation of economically valuable REEs from heavy metals.

Decontamination of Radioactive Cobalt, Nickel, Strontium, and Cesium from Simulate Solutions Using Tin Antimonate Columns

Abstract Three different tin antimonates with Sn:Sb ratios of 1:3.8, 1:1.2, and 13.5:1 were tested for decontamination of radionuclides (60Co, 63Ni, 137Cs, and 90Sr). The exchangers were tested in acidic solution (0.1 M HNO3) and in two floor‐drain water simulates containing Na+, Mg2+, and Ca2+ ions. High decontamination factors and processing capacities were obtained for Co, Ni, and Sr. The studied tin antimonates were applicable for column use, though clogging of the column beds did occur, particularly when treating high calcium concentration solutions.

Novel Antimonysilicate Material Quasar-N for the Removal of Radionuclides From Acidic Decontamination Liquids

Novel antimony silicate material, commercially available from PQ Corporation (previously Ineos Silicas) is highly selective for the removal of several key radionuclides (Co-60, Sr-90, Cs-137, Pu-236 and Am-241) from acidic and neutral nuclear waste effluents. The paper will summarise most the key results that have been obtained in the previous studies of the material. In addition, new test results on the removal Co-60, Sr-90, Cs-137 and Am-241 from acid media are reported. Static batch experiments and column experiments show that Am can be removed efficiently from nitric and oxalic acid, indicating that Quasar is suitable e.g. for the purification of acidic decontamination solutions.Copyright

Hydrolysis of Chelex 100 Chelating Resin and its Effect on Nickel Ion Exchange

Chelex 100 chelating resin in sodium form was found to be significantly hydrolysable. Contact with de-ionised water in solution volume to exchanger weight ratios of 10-4000 yielded a conversion to hydronium form of 1 to 10%. Hydrolysis brought sodium ions into solution with concentrations of 0.05-1.5 mM and increased the pH from 6.1 to 8.7-10.0. Hydrolysis has a marked effect on the nickel ion exchange on Chelex 100 in dilute nickel solutions (<0.1 mM): hydrolysis controls the sodium ion concentration in the solution and the increasing pH diminishes the absorption of nickel.