Ion exchangers in radioactive waste management: Natural Iranian zeolites (original) (raw)
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Cs+and Sr2+adsorption selectivity of zeolites in relation to radioactive decontamination
Journal of Asian Ceramic Societies, 2015
Zeolites are used as adsorbents of cationic elements in the radioactive decontamination process of water, soil and others. We determined Cs + and Sr 2+ adsorption selectivity of some zeolites to know effective zeolite species for the decontamination of radioactive Cs and Sr. A 30 mL mixed solution containing up to 15 mg L −1 of non-radioactive Cs + or Sr + and up to 0.50 M of Na + or K + was mixed with 0.5 g of Lindetype A, Na-P1, faujasite X, faujasite Y and mordenite. Among the zeolites, mordenite had the highest Cs + adsorption selectivity, and the selectivity had no correlation to the cation exchange capacity (CEC) of the zeolites. In contrast, Sr 2+ adsorption selectivity of the zeolites positively correlated with the CEC of the zeolites; Linde-type A with the highest CEC showed the highest adsorption selectivity, and its adsorption rate was more than 99.9% even in the presence of 0.5 M K +. A simulated soil decontamination experiment of Cs from a Cs-retaining vermiculite by using mordenite and that of Sr from a Sr-retaining vermiculite by using Linde-type A showed decontamination rates of more than 90%.
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.
Separation and Purification Technology, 2012
Sodium nonatitanate is a layered material that contains exchangeable sodium ions between layers. Zeolite A is an aluminosilicate structure that also contains exchangeable sodium ions inside the silica and alumina tetrahedral ''cages''. Both of these inorganic materials are known to selectively trap divalent metals. This paper describes the preparation/characterization of these inorganic samples and a comparative study of their sorption properties. Several types of experiments were performed: first, the experimental conditions for the sorption properties were assessed; then, the thermodynamics of sorption were studied; and finally, these two sorbents were compared in actual radioactive solutions (with low salinity and then with high salinity to simulate liquid waste from the Fukushima site). The maximum sorption capacity, the selectivity for Na/Sr and Ca/Sr, and the adsorption exchange free energy were obtained for the sodium nonatitanate and zeolite A samples. Sodium nonatitanate exhibited satisfactory decontamination properties for solutions with low amounts of calcium and was less affected by the presence of sodium when the strontium content was low. Zeolite A samples were also good candidates for strontium decontamination but were less efficient in a strong saline effluent.
Treatment of radioactive liquid waste by sorption on natural zeolite in Turkey
Journal of Hazardous Materials, 2006
Liquid radioactive waste has been generated from the use of radioactive materials in industrial applications, research and medicine in Turkey. Natural zeolites (clinoptilolite) have been studied for the removal of several key radionuclides (137 Cs, 60 Co, 90 Sr and 110m Ag) from liquid radioactive waste. The aim of the present study is to investigate effectiveness of zeolite treatment on decontamination factor (DF) in a combined process (chemical precipitation and adsorption) at the laboratory tests and scale up to the waste treatment plant. In this study, sorption and precipitation techniques were adapted to decontamination of liquid low level waste (LLW). Effective decontamination was achieved when sorbents are used during the chemical precipitation. Natural zeolite samples were taken from different zeolite formations in Turkey. Comparison of the ion-exchange properties of zeolite minerals from different formations shows that Gordes clinoptilolite was the most suitable natural sorbent for radionuclides under dynamic treatment conditions and as an additive for chemical precipitation process. Clinoptilolite were shown to have a high selectivity for 137 Cs and 110m Ag as sorbent. In the absence of potassium ions, native clinoptilolite removed 60 Co and 90 Sr very effectively from the liquid waste. In the end of this liquid waste treatment, decontamination factor was provided as 430 by using 0.5 mm clinoptilolite at 30 • C.
DESALINATION AND WATER TREATMENT
The pollution by heavy metal ions is a severe risk for aquatic and earthy living creatures. Ionexchange is an easy way to eliminate heavy metal pollution. Different ion-exchangers have been developed and applied for wastewater and other environmental treatments, such as zeolites. The synthesis of zeolites from inexpensive sources is very important in the minerals industry. The recycling of the waste aluminum foil to obtain the alumina source for the preparation of NaY zeolite and NaX zeolite was investigated in this study. Both Faujasite-type zeolites were obtained by a conventional hydrothermal treatment of the gel at 100°C for 24 h. The prepared zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by X-ray (EDAX), and nitrogen adsorption/desorption isotherms. The synthesized NaY zeolite and NaX zeolite based on aluminum foil had a Si/Al ratio of 2.28 and 1.35, and a specific surface area of 476.248 and 610.256 m 2 /g, respectively. Also, the treatment of the individual, binary, and ternary metals solutions containing Cd(II), Cu(II) and Hg(II) ions was carried out using ionexchange by NaY zeolite and NaX zeolite. The affinity of both zeolites to the selected metal ions was in the following order: Cd(II) > Cu(II) > Hg(II). The ion-exchange results highly adapted to the pseudo-second-order kinetic model with high correlation coefficients (R 2 > 0.96). Furthermore, stabilization of the removed ions inside the spent zeolites was conducted by geopolymers prepared from ordinary Portland cement and fly ash as cement material. Fly ash showed high potential as a solidifying material for the samples examined in the leaching test by H 2 SO 4 solution. The ratio of 1 cement:3 fly ash gave the least leached metals concentration at all testing conditions.
Sorption Behaviour of Armenian Natural Zeolites
Fusion Science and Technology - FUSION SCI TECHNOL, 2005
The sorptive behaviour of radioactive waste on Armenian zeolites, natural, irradiated, chemically treated and heated at high temperatures was studied and their capacity for the separation and enrichment of radionuclides was evaluated.The influence of temperature, acidity, basicity, specific activity, electron and gamma irradiation on sorption have been studied. The chemical analysis of exchanged samples was carried out and the cation exchange capacity was determined. Absorption properties of mono-cationic forms of different clinoptilolite samples were studied depending on type of guest cation and contact time.By means of model experiments the laboratory plant for absorption of metal cations from solutions in dynamic regime was designed and developed. This plant was used for experiments of radioactive waste removal from the Armenian nuclear reactor.
2021
The pollution by heavy metal ions is a severe risk for aquatic and earthy living creatures. Ionexchange is an easy way to eliminate heavy metal pollution. Different ion-exchangers have been developed and applied for wastewater and other environmental treatments, such as zeolites. The synthesis of zeolites from inexpensive sources is very important in the minerals industry. The recycling of the waste aluminum foil to obtain the alumina source for the preparation of NaY zeolite and NaX zeolite was investigated in this study. Both Faujasite-type zeolites were obtained by a conventional hydrothermal treatment of the gel at 100°C for 24 h. The prepared zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by X-ray (EDAX), and nitrogen adsorption/desorption isotherms. The synthesized NaY zeolite and NaX zeolite based on aluminum foil had a Si/Al ratio of 2.28 and 1.35, and a specific surface area of 476.248 and 610.256 m 2 /g, respectively. Also, the treatment of the individual, binary, and ternary metals solutions containing Cd(II), Cu(II) and Hg(II) ions was carried out using ionexchange by NaY zeolite and NaX zeolite. The affinity of both zeolites to the selected metal ions was in the following order: Cd(II) > Cu(II) > Hg(II). The ion-exchange results highly adapted to the pseudo-second-order kinetic model with high correlation coefficients (R 2 > 0.96). Furthermore, stabilization of the removed ions inside the spent zeolites was conducted by geopolymers prepared from ordinary Portland cement and fly ash as cement material. Fly ash showed high potential as a solidifying material for the samples examined in the leaching test by H 2 SO 4 solution. The ratio of 1 cement:3 fly ash gave the least leached metals concentration at all testing conditions.