Behaviour of Ion Exchange Resins and Corrosion Inhibitors in Dilute Chemical Decontamination

Ethylene diamine tetra acetic acid (EDTA) is a versatile complexing agent and is being employed in decontamination formulations. The dilute chemical decontamination (DCD) process employs ion exchange resins for regeneration of complexants, collection of metal ions/active isotopes and for removal of the decontaminating chemicals. In this work the interactions of EDTA on cation and anion exchange resins have been studied. The pickup of EDTA on cation exchange resin is by ion exchange mechanism and not possibly by precipitation at the low pH existing in ion exchange resin matrix. A mathematical relationship has been worked out to calculate the amount of EDTA adsorbed per unit volume of the cation exchange resin at a given pH. In addition, the behaviour of DTPA, HEEDTA and NTA on cation exchange resin has been evaluated. The chromatographic behaviour of OH- form of strong base anion exchange resin for a formulation containing EDTA, oxalic acid and citric acid has been reported and its relevance to the decontamination process has been discussed.

Even though the corrosion rate of DCD is very low on most of the materials of construction, influence of time, temperature and the composition of the formulation on carbon steel is studied. Different classes of inhibitors were evaluated for reducing carbon steel corrosion.     

Effect of Metallic Impurities on Oxidation Reaction of Ion Exchange Resin, (II)

The catalytic effect of six metallic impurities on the oxidation reaction of cation exchange resin was investigated. The impurities, which were originally adsorbed onto the resin by an ion exchange method, combined with S present in the functional sulfonic acid group during heat-treatment in a nitrogen atmosphere to give the metal sulfides. The sulfides were subsequently oxidized to metal oxides.

In the case of Pd²⁺, Cu²⁺, Fe²⁺ and Fe³⁺ impurities, their sulfides were easily converted into oxides, which catalyzed the resin oxidation. Their catalytic activities depended on the heat of formation of the catalyst oxides ΔH‘₀; the lower was ΔH’₀, the more active the catalyst was. However, Co²⁺ and Ni²⁺ impurities had relatively low catalytic activities. This was because Co and Ni sulfides slowly changed into oxides, and the main chemical compositions of the impurities were not oxides but sulfides, which had no catalytic effect on the resin oxidation.     

The Application of an Advanced Ion Exchange Process to Reprocessing Spent Nuclear Fuels, (I)

In order to develop an advanced ion exchange process for the reprocessing of spent nuclear fuels, a novel anion exchanger, AR-01 with the resin embedded in porous silica beads and benzimidazoles as functional groups has been manufactured. Adsorption behavior of various fission product elements (FPs) and uranium in nitric acid medium were investigated experimentally using this anion exchanger. Separation performance of FPs from U(VI) in simulated spent fuel solutions was demonstrated by column chromatography utilizing dilute HNO₃ and thiourea as eluents.

Most FPs such as Cs(I), Sr(II), Mo(VI), Rh(III) and trivalent rare earths showed negligibly slight adsorption and could be separated from U(VI) satisfactorily. Cerium(IV) was strongly adsorbed, but was gradually reduced to non-adsorptive Ce(III) by the anion exchanger. Zirconium(IV) presented weak adsorption and its a part mixed with U(VI) in the column experiments. Ruthenium(III) exhibited quite strong adsorption in a broad HNO₃ concentration range as the form of anionic nitrosylnitrato-complexes, its most amount mixed with U(VI). Palladium(II) showed significantly strong adsorption probably due to complexes formation with the anion exchanger. The adsorbed Pd(II) was effectively eluted out by thiourea and separated from U(VI) and other FPs completely.     

Simultaneous Adsorption of Cs-137 and I-131 from Water and Milk on “Metal Ferrocyanide-Anion Exchange Resin”

“Metal ferrocyanide-anion exchange resin”, which is made by precipitating the metal ferrocyanide in an anion exchange resin matrix, has been used for selective adsorption of Cs ion in a variety of aqueous solutions.

The “resin” has both properties of metal ferrocyanide and anion exchange resin. Therefore, we tried simultaneous adsorption of radiocesium and radioiodine from water and milk on the “resin”.

Results showed that “metal ferrocyanide-anion exchange resin” such as Cu, Fe and Ni ferrocyanide can be used for a rapid and simple concentration of radiocesium and radioiodine quantitatively from a large volume of sample solutions.

This paper also touches upon the removal of ¹³⁷Cs and ¹³¹I in rain water and milk collected in Japan after the Chernobyl accident.     

Incorporation of Radioactive Spent Ion Exchange Resins in Plastics

Experiments were undertaken on the incorporation in plastics—polyethylene in particular—of radioactive spent ion exchange resins produced in nuclear power plants. The resulting polyethylene products burdened with radioactive resin were tested to ascertain the properties considered important for radioactive waste management. The items chosen for testing were mechanical strength, leachability of radionuclide and radiation resistance. Polyethylene products burdened with 50w/o of resin were found to possess an impact strength of 10kg-cm/cm and a compressive strength of 300 kg/cm², which values do not indicate any appreciable decrease in mechanical strength compared with polyethylene unburdened with resin. The leaching rate of ¹³⁷Cs from the resin- burdened polyethylene product was very small—only 0.1% leached out in one year. In respect of decomposition by radiation, the amount of gases evolving upon absorbing a dose of 10⁹ rad was 10 ml/g. The effect of radiation on the mechanical strength was also studied.

It is concluded from above results that solidification of radioactive spent ion exchange resin by incorporation in plastics is one of the best methods devised so far for treating spent resins.     

Adsorption Behavior of Americium on Zeolites

Zeolites are expected to be used in buffer materials as an admixture to bentonite to increase their ion exchange ability. The behavior of ion exchange adsorption of Am³⁺ on various zeolites was examined by batch and column methods. The distribution coefficient of Am³⁺, K_d, increased with equilibrium pH from 1.5 to 4.0. L zeolite and mordenite having large pore size yielded relatively large values of K _d over 10³ at pH 3.0. The K _d for L zeolite was unaffected by the concentration of coexisting cations, i.e. Na⁺ up to 0.1 M, and K⁺, Ca²⁺ and Mg²⁺ less than 0.01 M. The Am³⁺ ion was not detected in the effluent passed through the L zeolite column up to 90 bed volumes, even when the feed solution contained a relatively large amount of Na⁺-0.5 M. Americium ion adsorbed on zeolites could be quantitatively eluted with 0.1 M nitric acid.     

Extraction mechanisms of uranyl ions by 1-butyl-3-methylimidazolium nonafluorobutanesulfonate containing N-dodecyl-2-pyrrolidone

Extraction of U(VI) in HNO₃ to 1-butyl-3-methylimidazolium nonafluorobutanesulfonate (BMINfO) by using N-dodecyl-2-pyrrolidone as an extractant has been investigated. With increasing the concentration of HNO₃ from 0.01 to 3.0 mol/dm³ (M), distribution ratio decreased. This suggests that uranyl ions are extracted by ion exchange with a cation component of BMINfO, i.e. BMI⁺. The amount of BMI⁺ transferred to aqueous phase accompanied by extraction of U(VI) was evaluated with ¹H NMR measurement. Plots of the amount of U(VI) extracted versus the amount of BMI⁺ transferred from BMINfO phase to the aqueous phase indicated linear relationship. The slope of the line was about 1.0 and 0.63 in the extraction system of U(VI) performed in 0.1 and 1.0 M HNO₃, respectively. This result means that two types of extraction mechanisms exist depending on the concentration of HNO₃. One is the ion exchange mechanism. Another is the ion-pair extraction mechanism.     

Recovery of palladium by silica/polymer-based 2,6-bis(5,6,7,8-tetrahydro-5,8,9,9-tetramethyl-5,8-methano-1,2,4-benzotriazin-3-yl)pyridine adsorbents from high level liquid waste

The adsorption properties of a porous silica-based adsorbent 2,6-bis(5,6,7,8-tetrahydro-5,8,9,9-tetramethyl-5,8-methano-1,2,4-benzotriazin-3-yl)pyridine (Me₂-CA-BTP/SiO₂-P) towards Pd(II) were investigated. The adsorption ability of Me₂-CA-BTP/SiO₂-P towards Pd(II) increased dramatically with the increase of HNO₃ concentration and showed a saturated uptake of Pd(II) after the HNO₃ concentration reached 3 mol/dm³. It was found that nitrate ion would participate in the adsorption reaction. Palladium adsorption kinetic and isotherm were in accordance with the pseudo-second-order rate law and Langmuir isotherm adsorption model, respectively. Thiourea could effectively elute the adsorbed palladium from Me₂-CA-BTP/SiO₂-P. Adsorption studies with high level liquid waste elements showed a high selectivity towards Pd(II) over other fission product elements in ≥3 mol/dm³ HNO₃ solution. The stability of Me₂-CA-BTP/SiO₂-P against HNO₃ was satisfied for the reason of the adsorption performance keeping for Pd(II) after a long-time contact with HNO₃ solution. The adsorbent performed good γ-irradiation stability in dry state and low concentrations of HNO₃. The presence of HNO₃ enhanced the radiolysis and the adsorbent still reserved a presentable adsorption amount after γ-irradiation in 3 mol/dm³ HNO₃.     

Effect of Gamma-Irradiation on Cation Exchange Resin

Several forms of cation exchange resins with different crosslinkages have bsen subjected to ⁶⁰Co γ-radiation, in wet or dry state and the effects of such variables as adsorbed ionic species, crosslinkage of the resin, and the water content in the resin on radiation damage to organic resin have been examined in their relation to γ-radiation dose. The result showed that radiation caused marked changes in the chemical and physical properties of the resin, and phenomena such as de-crosslinking, loss of strong-acid capacity, formation of a functional group composed of a weak-acid exchange group were observed. The degree of such degradation phenomena was not affected by adsorbed ions when their valency states were kept unchanged during irradiation, but when the adsorbed ions were reduced during exposure, the extent of degradation was found inhibited to a significant extent. It may be concluded from the results that the decomposition of the cation exchange resin is mainly initiated by reaction with the resin produced by radiation-formed reducing species, i.e., H atoms. A mechanism of resin degradation is also proposed.     

Feasibility studies on the selective separation of fission palladium(II) by isoHex-BTP/SiO2-P adsorbent from HLLW

Aiming at the selective recovery of fission palladium(II) from high-level liquid waste (HLLW), the silica/polymer (SiO₂-P)-based isoHex-BTP adsorbent (isoHex-BTP/SiO₂-P) was synthesized by impregnating complexing agent isoHex-BTP into the multiporous SiO₂-P inert support. The feasibility of separation of Pd(II) from HLLW by isoHex-BTP/SiO₂-P was evaluated by batch experiment method. The results showed that isoHex-BTP/SiO₂-P exhibited much higher adsorption selectivity for Pd(II) than the other fission products, even Am(III) and Pu(IV) presented in HLLW. The ideal nitric acid concentration for the adsorption of Pd(II) by the adsorbent was shown to be ≥2 mol dm^–3. The adsorption of Pd(II) fits well to the pseudo-second-order kinetic model and Langmuir isotherm model. Quantitative Pd(II) desorption was achieved by using 0.5 mol dm^?3 SC(NH₂)₂ - 0.1 mol dm^?3 HNO₃ solution.     

Free Energy of Formation for Solid Lithium Nitride

Breakthrough properties of Cs were examined at 298 K using columns packed with K⁺ forms of ferrierites. Breakthrough curves showed symmetrical S-shaped profiles at lower space velocity (SV) below 50/h. The adsorption zone of Cs increased linearly with flow rate and exceeded the length of packed column over 50/h. The S-shaped curves were obtained at lower HN0₃ concentrations below 1 mol/dm³, whereas Cs readily flowed out through the column in the presence of 5 mol/dm³ HNO₃. The break point was shifted to lower bed volumes with increasing concentration of coexisting cations; the amounts of Cs adsorbed were lowered in the presence of competing cations in the order, Na⁺>K⁺>Rb⁺. Cesium adsorbed on ferrierites could be quantitatively eluted with 1 mol/dm³ KNO₃ as an eluent. The selective removal of Cs was achieved by passing the simulated radioactive liquid wastes through the ferrierite columns.     

Reduction of Cesium Leaching Ratio from Cementitious Resin Forms Using Natural Active Silica

Cesium adsorption behavior of active silica, which is a natural acid clay composed of cristobalite and quartz, was evaluated for its applicability as Cs adsorbent to be added to cementitious waste forms containing spent ion exchange resin. Since active silica carried the Cs exchangeable silanol group (—SiOH) originally, the Cs distribution coefficient was remarkably high (<10⁴). It increased in saturated Ca(OH)₂ solution, simulating the cement paste, due to formation of new silanol groups. With its addition to the cementitious forms with ¹³⁴Cs adsorbed ion exchange resin solidified by slag cement, the Cs leaching ratio was reduced to below 1/10 that without active silica.     

季铵树脂上硫酸铀酰络离子的红外光谱研究

本文用红外光谱研究了季铵树脂吸附的硫酸铀酰络合物。树脂吸附UO_2(SO_4)_2~(2-)时,UO_2~(2+)的γ_3峰值为918cm~(-1),吸附UO_β(SO_4)_3~(4-)时,该峰值为910cm~(-1)。树脂在组成接近铀水冶条件的吸附液中吸附平衡后,吸附n值为2.5—2.7的UO_2(SO_4)_n~(2-2n),其UO_2~(2+)的γ_3峰与树脂的季铵峰合并于900cm~(-1);该树脂在KBr压片中会发生转换反应,使硫酸铀酰络离子转成UO_2(SO_4)_2~(2-)和SO_4~(2-)。还利用红外光谱定量测定反应终了的自由硫酸根量,在化学当量法求得的树脂吸附铀量及SO_4~(2-)量基础上,计算了n值。     

微波消解-原子吸收法应用于核级树脂锂型转型率的分析研究

常规核级离子交换树脂锂型转型率的测量采用将离子交换树脂中的锂用酸淋洗后测量锂浓度,再计算锂型转型率,存在分析时间长、分析结果偏低等不足。本文采用微波消解-原子吸收法测量核级离子交换树脂的锂型转型率,利用微波消解实现树脂的完全消解,利用原子吸收仪测量锂浓度,结合氢型树脂湿基工作交换容量计算离子交换树脂的锂型转型率,实现离子交换树脂锂型转型率的准确测量。分析结果表明,锂浓度加标回收率为99%,相对标准偏差为0.97%（n=7）,锂型转型率达99.20%。方法具有离子交换树脂使用量少、分析结果准确等优点,可用于核级离子交换树脂锂型转型率的测量。      

铀的离子交换反应——Ⅳ.盐酸介质中铀(Ⅵ)在强碱性阴离子交换树脂上的化学状态

用当量计算、分配比的测定以及红外光谱等三种实验方法,证明从盐酸介质中吸附到强碱性阴离子交换树脂上的铀酰,主要是以(UO_2Cl_4)~(2-)存在。     

Influence of ion exchange resin on the performance of continuous electrodeionization (CEDI) treating low-level radioactive wastewater

With the fast development of nuclear power, low-level radioactive wastewater (LLRW) treatment will meet more severe requirements. Continuous electrodeionization (CEDI) is a novel technology to treat LLRW with advantages of lower level effluent and smaller waste production. In this study, the influences of ion exchange resins (IERs) in the concentrate and dilute compartments on the performance of CEDI were investigated. The three stacks filled with anion exchange resins in the dilute compartments were more efficient for boron removal than metal ions, while the three stacks filled with cation exchange resins were more efficient for the removal of metal ions than boron. The stack filled with a type of mixed IERs was good at removing both metal ions and boron. The correlation analysis showed that no significant correlations were found between ion exchange capacities or ion exchange kinetics with the decontamination factors of metal ions. The removal ratios of boron were positively correlated with the ion exchange capacities, but were not correlated with the ion exchange kinetics. The results can guide the CEDI stack design by filling different IERs for different purposes.     

Synthesis of a Magnetic Composite Resin and Its Cobalt Removal Characteristics in Aqueous Solution

A series of stepwise procedures to prepare a new organic-inorganic composite magnetic resin with phenolsulphonic-formaldehyde and freshly formed iron ferrite was established, based upon wet-and-neutralization method for synthesizing iron ferrite and pearl-polymerization method for synthesizing rigid bead-type composite resin. The ion exchange and sorption characteristics of the composite resin prepared by the above method at various conditions were experimentally disclosed. The composite resin prepared shows stably high removal efficiency to Co(II) species in aqueous solution in a wide range of solution pH. The overall isotherm is qualitatively explained by the generalized adsorption isotherm concept proposed by McKinley. The standard enthalpy change derived from van't Hoff equation conforms to the typical range for chemisorption or ion exchange. The selectivity of the PSF-F (phenolsulphonic formaldehyde-iron ferrite) composite resin to Co(II) species and other competing chemicals (i.e. Na₂EDTA, Ca(II) and Na) was compared. It is anticipated that the composite resin can also be used for column-operation with process-control by applying external magnetic field, since the rigid bead-type composite resin shows magnetic-susceptibility due to its paramagnetic inorganic constituent (i.e. iron ferrite).     

Application of photoluminescence microspectroscopy: a study on transfer of uranyl and europium ions on dry silica gel plate

ABSTRACT

When water contacts with porous materials, water and chemical species dissolved in the water transfer into the inside of the porous materials. Here, to study the transfer of uranyl and europium ions on a dry silica gel plate, we dropped a small amount of aqueous solution (~0.5 μL) dissolving the two ions on a dry silica gel plate, and the distributions of the two ions spread on the silica gel plate were observed by photoluminescence microspectroscopy. Photoluminescence images of uranyl and europium ions clearly show that when uranyl ion coexists in the solution, europium ion transfers in a larger area compared to uranyl ion. It can be interpreted that the larger-area distribution of europium ion is caused because uranyl ion is preferentially adsorbed to silica gel and the uranyl adsorption disturbs the adsorption of europium ion. The coexistence of uranyl ion may influence the mobility of other ion species.     

放射性废离子交换树脂高温裂解处理技术研究

通过热重实验以及台架试验,进行了废阴/阳离子交换树脂的高温裂解处理技术研究。结果表明,通过电磁感应加热反应器中的金属球并辅助搅拌,可以实现树脂的高温裂解。相比于氮气和水蒸气,空气是更合适的反应气氛。在空气氛围下,当树脂处理量为1 kg/h时,设定空气流量2 m³/h,反应温度600 ℃～700 ℃,添加剂选择CuSO₄·5H₂O,阴/阳离子交换树脂经本裂解工艺处理,废物残留率分别为8%和12%左右,两种树脂最终的裂解残留率可以达到3%～5%左右,可以实现较为彻底的裂解反应。阴离子和阳离子交换树脂的裂解反应有明显的区别,其中阴离子交换树脂热敏性更高,裂解需要的温度和空气流量更低,但反应更剧烈,烟气量更大。     

Hydrous Titanium Oxide Ion Exchanger, (I)

Abstract

Synthesis of hydrous titanium oxide ion exchanger was tried from three systems: (a) TiCl₄-NaOH-H₂O, (b) ATS (ammonium titanyl sulphate monohydrate)-NaOH-H₂O and (c) TiCl₄-NH₄OH-H₂O. The first method gave the best results under the conditions covered in the present work.

It was found that repeated washing and aging of the hydrous titanium oxide precipitate were indispensable in order to obtain reproducible results, and that this operation further obviated the need of precisely adjusting the conditions for mixing the reagents.

Both the yield of exchanger and the ion exchange capacity of the resulting product increase with concentration of the reagents. A cation exchange capacity of about 3 meq·Na⁺/g could be obtained, which is considerably higher than any corresponding value reported in literature. The value decreased with increasing drying temperature. Irrespectively of the conditions of synthesis, the chemical composition was TiO₂·(2.0–2.2) H₂O, and the impurities contained in the product were found to be less than 0.1%. The exchanger produced is in granular form suitable for use in column operation. It is fairly stable in alkaline solution, and also in mineral acid solutions of <0.1 n concentration.