Uptake Of Cs Research Articles

Boosting cesium retention efficiency with polyoxometalate-ionic liquid composites: Insights into {WO6} octahedral affinity

Commonly used polyoxometalate (POM) adsorbents exhibit high cesium (Cs) adsorption capacity. However, its impotent ability to sequester adsorbates poses a risk of Cs migration in radioactive waste decontamination and disposal. By leveraging the cesium affinity of POMs and the regulatory properties of ionic liquids (ILs), POM-IL composites hold promise for mitigating the risk of cesium migration through efficient adsorption and retention. Herein, we designed two POM-ILs composed of the phosphotungstate anion (PW) and tetrabutylammonium cation (TBA), i.e., the {WO6}-saturated TBA-PW12 and mono-lacunary TBA-PW11, for the capture and retention of aqueous Cs. The composites were then characterized, and the performance and mechanism of Cs uptake were investigated. TBA-PW12 exhibited ∼300 nm aggregate of particles around 20–60 nm. TBA-PW12 retained the Keggin structural features of PW12O403−, which was proven essential for the binding of Cs+. With a retention efficiency of 97.3% in an NH4Cl eluent and a maximum adsorption capacity of 400.9 mg/g at 338 K, TBA-PW12 exhibited superior Cs capture and retention compared to the POM-IL derived from common Cs adsorbent phosphomolybdate. The Cs adsorption onto TBA-PWs achieved equilibrium within 180 min. Cs uptake by TBA-PWs was monolayer chemisorption of Cs+ accompanied by H+ release, and the removal efficiencies stabilized around initial pH 5–10. Due to intense affinity between {WO6} and Cs+, TBA-PW12 efficiently sequestered Cs + through {WO6} octahedra so that the {WO6}-saturated TBA-PW12 presented better Cs uptake performance than the mono-lacunary TBA-PW11. The IL anion [N(C4H9)4]+ provided a composite-water biphasic interface for aqueous Cs adsorption, while retaining the ability of POM cation PW12O403− to form a stable structure with Cs via its affinity to {WO6} octahedra. These findings support the design of POM-IL composites as efficient adsorbents for capturing and retaining Cs, aiding in the decontamination and safe disposal of radioactive waste, thereby minimizing the risk of nuclide leakage into the environment.

High-affinity potassium transporter TaHAK1 implicates in cesium tolerance and phytoremediation

Cesium (Cs) is a toxic alkaline metal affecting human health. Plant high-affinity K transporters (HAKs) involved in Cs uptake and transport have been identified in several plants. However, the molecular regulatory mechanisms of Cs uptake and transport, and homeostasis between Cs and K by HAKs remain unknown. In this study, TaHAK1 was overexpressed in rice (TaHAK1-OEs) to evaluate Cs absorption capacity and the Cs and K homeostasis mechanisms. Results showed that TaHAK1 promoted seedling growth by fixing Cs in the root cell wall and modifying Cs distribution. Transcriptome and bioinformatics analyses revealed that 37,828 differentially expressed genes (DEGs) were significantly induced in TaHAK1-OEs, of which the pathways involved in cell wall biosynthesis and ion absorption transport were notably affected including genes, XTHs, CSLEs, HAKs, and ABCs. Moreover, under Cs-contaminated soil, TaHAK1-OEs exhibited improved Cs tolerance by decreasing Cs accumulation and increasing K content in different tissues, particularly in the grains, indicating that TaHAK1 acts as a candidate gene for screening genetic modification of Cs phytoremediation and developing low-Cs-accumulation rice varieties. This study provides new insights into the uptake and translocation of Cs and the homeostasis of Cs and K in plants, and also supplies new strategy to improve phytoremediation efficiency.

Long-term effects of potassium chloride, wood ash, and EDTA on 137Cs soil-plant transfer in a mixed forest of Ukraine

We conducted a 10-year field experiment to study the effects of potassium chloride, wood ash, zinc, and manganese on reducing 137Cs uptake by young leaves and green shoots of common dwarf shrubs and tree species near the Chornobyl Nuclear Power Plant. A field experiment had four treatments: a control with no fertilisation, and three fertilised treatments: potassium fertiliser (KCl), a combination of potassium fertiliser and wood ash (KCl + Ash), and a solution providing zinc and manganese (EDTA). There was approximately 30 % decrease in 137Cs uptake by most of the studied plants species growing on plots fertilised with KCl compared to unfertilised plots during intermediate (2014–2016) and late (2018–2021) periods. Combining KCl with wood ash was found to be the most effective countermeasure, reducing 137Cs uptake by up to 60% in most species, while treatment with EDTA was less effective. Generally, the decline in 137Cs uptake by plants over the study years following treatments with fertilisers was more pronounced than in the control, indicating the efficiency of fertilisation in reducing 137Cs uptake by forest plants. Our research suggests that a combination of potassium chloride and wood ash can still effectively reduce 137Cs transfer in most common forest species, even years after the accident.

Correlating shale geochemistry with metal sorption: influence of kaolinite content

ABSTRACT Argillaceous rocks constituting clay fractions are potential host rock candidates for isolation of radioactive waste in underground repositories. The present study aims at characterization of two argillaceous rocks (shales) from different geological settings (surface and subsurface localities) and investigation of their cesium (Cs) sorption behaviour. The shales were characterized using various analytical techniques to evaluate the textural attributes, mineralogical constituents and surface properties. The major mineralogical constituent of the surface and subsurface shale was quartz (62%) and kaolinite (56%), respectively. The abundance of smectite and illite in both the shales was comparable. Fluorescence and UV-Vis spectra confirmed the presence of polyaromatic hydrocarbons (PAHs) in the subsurface shale. The subsurface shale demonstrated higher Cs retention (17 mg g−1) than the surface shale (12 mg g−1) due to higher kaolinite content. Surface analysis of the shale samples revealed involvement of ion exchange mechanism in Cs uptake. The agreement of experimental results with Freundlich sorption isotherm suggests the heterogenous nature of the shales with multiple sorption sites. The correlation of geochemistry (especially the kaolinite content) for both the shales with Cs sorption is clearly highlighted in the present studies. The present investigation implies the applicability of the studied shales for waste management applications.

Sorption Efficacy of Weathered Basalt Rock for Metal Ions of Nuclear Importance

Background:: A safe and long-term isolation of radionuclides is crucial for efficient waste management in the nuclear fuel cycle. Clay minerals of geological origin are considered candidate barrier materials for the sequestration of nuclear waste for geological disposal applications. Objective:: The present study encompasses a systematic characterization of weathered basalt rock and the influence of its constituent clay minerals (formed mainly due to the weathering process) in the uptake of metal ions of nuclear importance, such as cesium (Cs+) and strontium (Sr2+). Methods: The structural profile of the weathered basalt has been investigated using different analytical techniques, including polarizing microscope, XRD, FTIR and EDXRF. The sorption behaviour of the rock sample for Cs+ and Sr2+ has been investigated in a comprehensive batch mode by varying the experimental conditions. The analytical findings for structure and batch sorption performance of the material have been further correlated to understand the influence of different parameters on the uptake of metal ions and the underlying mechanism. Results:: Structural analyses confirmed the presence of clay minerals viz., kaolinite, illite and montmorillonite in the sample. A comprehensive sorption performance assessment carried out in batch mode at different experimental conditions revealed that the uptake of both the metal ions was rapid and dependent on initial metal ion concentration and solution pH. The uptake of Cs+ ions was found to be higher as compared to the Sr2+ ions. EDXRF analysis confirmed the loading of Cs+ and Sr2+ on the weathered basalt. Experimental batch sorption data presented a better agreement with the theoretical Freundlich isotherm pertaining to the heterogeneous nature of the sorbent. Conclusion:: The studies highlight that the clay minerals formed by structural alteration of basalt rock upon intense weathering could be very useful in fixing the nuclear fission waste components such as Cs+ and Sr2+.

Uptake from water and depuration of 137Cs and 90Sr by silver Prussian carp (Carassius gibelio)

To follow up field observations in the Chornobyl Exclusion Zone (ChEZ), a series of controlled model aquarium experiments were conducted to determine the uptake and depuration rates of 137Cs and 90Sr in silver Prussian carp (Carassius gibelio) in fresh water, varying in temperature from 5 to 27 °C, with daily feeding rates of 0–1.5 % fish weight day−1.In the present study, the 137Cs uptake rates in muscle tissues directly from water, 0.05–0.09 day−1 at temperatures of 5–27 °C, were significantly lower than previously reported for fish fed under natural conditions in contaminated lakes within the ChEZ. The rate of 90Sr uptake in bone tissues of silver Prussian carp varied from 0.055 day−1 at a water temperature of 5 °C and feeding rates ≤0.15 % fish weight day−1 to 1.5 ± 0.2 day−1 at a temperature of 27 ± 1 °С and at the highest tested feeding rate of 1.5 % day−1.The rate of decrease of 137Cs concentration in muscle tissues was kb = 0.0028 ± 0.0004 day−1 (T1/2 = 248 ± 35 days) at the lowest water temperature tested (5 °С). At water temperatures between 13 and 26 °С and a feeding rate of 0.15 % day−1, the rate increased to kb = 0.0071–0.0092 day−1 (T1/2 = 75–99 days).The rates of decrease of 90Sr activity concentration in bone tissues at water temperatures between 22 and 25 °С and a feeding rate of 0.5 % day−1 were kb=0.004–0.0014 day−1, and the associated biological half-life T1/2 ranged 50–160 days, respectively. The present work supported conclusions related to the main pathways of 137Cs and 90Sr uptake by silver Prussian carp, and demonstrated the usefulness of combining field and laboratory uptake and depuration experiments.

Reduction‐Induced Uptake of Cs+ in Metal–Organic Frameworks Loaded with Polyoxometalates (Small 17/2024)

Reduction‐Induced Uptake of Cs⁺ in Metal–Organic Frameworks Loaded with Polyoxometalates (Small 17/2024)

Reduction-Induced Uptake of Cs+ in Metal-Organic Frameworks Loaded with Polyoxometalates.

Materials for Cs+ adsorption continue to be important for the treatment of various solutions. Metal-organic frameworks (MOFs) with large specific surface areas promise adsorption properties for various gases, vapors, and ions. However, the utilization of MOFs for alkali ion capture, specifically, Cs+ capture is still in its infancy. Herein, MOFs are hybridized with polyoxometalates (POMs) to study the effect of i) MOF type, ii) POM type, and iii) POM loading amounts on Cs+ capture. In particular, the composite of ZIF-8 and [α-PMo12O40]3- (PMo12/ZIF-8) adsorbed Cs+ ions effectively when compared to pristine ZIF-8. In addition, the reduction of Mo within the POM from MoVI to MoV by ascorbic acid during the Cs+ uptake process doubled the Cs+ uptake capacity of PMo12/ZIF-8. This observation can be attributed to the increased overall negative charge of the POM facilitating Cs+ uptake to compensate for the charge imbalance. Hybridization with other MOFs (MIL-101 and UiO-66) largely suppresses the Cs+ uptake, highlighting the importance of hydrophobicity in Cs+ capture. Furthermore, PMo12/ZIF-8 led to an outstanding Cs+ uptake (291.5mg g-1) with high selectivity (79.6%) from quinary mixtures of alkali metal cations even among other representative porous materials (Prussian blue and zeolites).

Insight to the cesium entrapment by natural shale: implications to geological disposal of nuclear waste

ABSTRACT The knowledge of radionuclides sorption behavior of various site-specific heterogeneous geosystems is essential for developing different clean-up strategies and predicting the radiological risks for long term. The present study is aimed at understanding the mineralogical and textural characteristics of natural shale rock (sampled from Kachchh Basin of Gujarat, India) and its correlation with cesium (Cs) sorption behavior. The modal mineralogical composition, textural attributes, petrophysical properties, surface functionalities and morphology of shale were evaluated. Clay minerals (smectite, kaolinite and illite) constitute more than 40% of the shale along with the major component- quartz. A comprehensive Cs batch sorption study performed at varying experimental parameters demonstrated that the maximum Cs retention of shale was 34.80 ± 2.85 mg g−1 in the studied concentration range. Sorption equilibrium data agreed well with Freundlich isotherm, highlighting the heterogeneity of shale. Variation in solution pH (in the range of 6–10) during sorption demonstrated the buffering of solution in near neutral range indicating the role of cations (available in the interlayers of clay minerals) in Cs uptake. Alternatively, the presence of illite mineral in the shale with known frayed edge sites contributed to the irreversibility of sorption event. The present studies illustrate the potential of shale as host rock for its application in nuclear waste management.

Differentiation between chemo- and radiotoxicity of 137Cs and 60Co on Lemna minor

The uptake and effects of stable Cs and Co on L.minor were extensively studied, together with the effects of gamma radiation using a 137Cs or 60Co source. Innovative is that we combined external irradiation (from 137Cs or 60Co sources) with the direct uptake of certain amounts of stable Cs or Co to simulate the impact of the same mass of a radioisotope compared with that of the stable element. Such approach allows to differentiate between chemo- and radiotoxicity of 137Cs or 60Co, permitting to study the 137Cs and 60Co uptake by L. minor without using high concentrations of these elements in solution. Our results indicate that radiotoxicity of both 137Cs and 60Co has a greater importance compared to their chemotoxicity. This was also supported by the independent action and concentration addition concepts. Both concepts resulted in a good prediction of the dose-response curve of the combination exposure. The maximal removal of 137Cs or 60Co per gram dry matter of L. minor was lower compared with the removal of the corresponding stable isotope. The toxicity of 60Co was higher compared to 137Cs based on EC50 values and uptake data. With respect to the effects on photosynthetic pigments, starch and soluble sugars contents, only starch increased in a concentration- and dose-dependent manner.

Layered metal sulfides with MaSbc- framework (M = Sb, In, Sn) as ion exchangers for the removal of Cs(Ⅰ) and Sr(Ⅱ) from radioactive effluents: a review.

Nuclear power has emerged as a pivotal contributor to the global electricity supply owing to its high efficiency and low-carbon characteristics. However, the rapid expansion of the nuclear industry has resulted in the production of a significant amount of hazardous effluents that contain various radionuclides, such as 137Cs and 90Sr. Effectively removing 137Cs and 90Sr from radioactive effluents prior to discharge is a critical challenge. Layered metal sulfides exhibit significant potential as ion exchangers for the efficient uptake of Cs+ and Sr2+ from aqueous solutions owing to their open and exchangeable frameworks and the distinctive properties of their soft S2- ligands. This review provides a detailed account of layered metal sulfides with MaSb c- frameworks (M = Sb, In, Sn), including their synthesis methods, structural characteristics, and Cs+ and Sr2+ removal efficiencies. Furthermore, we highlight the advantages of layered metal sulfides, such as their relatively high ion exchange capacities, broad active pH ranges, and structural stability against acid and radiation, through a comparative evaluation with other conventional ion exchangers. Finally, we discuss the challenges regarding the practical application of layered metal sulfides in radionuclide scavenging.

Modeling long-term transfers of radiocesium in farmland under different tillage and cover crop treatments

The 2011 nuclear accident at Japan's Fukushima Daiichi Nuclear Power Plant (FDNPP) prompted inquiries about the long-term transfer of Cesium-137 (137Cs) from soil to agricultural plants. In this context, numerical modeling is particularly useful for the long-term evaluation of the consequences of agroecosystem contamination. Agricultural practices, such as tillage and cover cropping, play key roles in 137Cs recycling in agroecosystems. In this study, we used 10-year monitoring data to develop a dynamic model to predict 137Cs redistribution (via uptake, litterfall, translocation, and percolation) under different tillage (no-tillage, NT; rotary cultivation, RC; moldboard plow, MP) and cover crop (rye; hairy vetch; fallow weed) treatments. The verification exercise and assessment results indicated the model's reliability, as the temporal dynamics of predicted values agreed with observed values. Tillage significantly influenced the 137Cs distribution in soil, thereby decreasing plant uptake of 137Cs, whereas cover crop exerted a minimal effect on 137Cs cycling. Furthermore, while the 137Cs concentrations in soybean grain under RC and NT treatments were comparable 62 years after the FDNPP accident, the concentration under MP treatment remained consistently the lowest. Despite natural decay being the main cause of the decreased global 137Cs level in the agroecosystem, with minimal losses from percolation to deeper soil layers and soybean harvesting, adopting an appropriate tillage practice was shown to promote a long-term reduction of 137Cs concentration in crops. Finally, to improve the model's accuracy, further research should consider incorporating the effects of soil properties and extreme weather events on 137Cs flow into the model, as these factors are essential for realizing improved agroecosystem predictions.

Xylem K+ loading modulates K+ and Cs+ absorption and distribution in Arabidopsis under K+-limited conditions.

Potassium (K+) is an essential macronutrient for plant growth. The transcriptional regulation of K+ transporter genes is one of the key mechanisms by which plants respond to K+ deficiency. Among the HAK/KUP/KT transporter family, HAK5, a high-affinity K+ transporter, is essential for root K+ uptake under low external K+ conditions. HAK5 expression in the root is highly induced by low external K+ concentration. While the molecular mechanisms of HAK5 regulation have been extensively studied, it remains unclear how plants sense and coordinates K+ uptake and translocation in response to changing environmental conditions. Using skor mutants, which have a defect in root-to-shoot K+ translocation, we have been able to determine how the internal K+ status affects the expression of HAK5. In skor mutant roots, under K+ deficiency, HAK5 expression was lower than in wild-type although the K+ concentration in roots was not significantly different. These results reveal that HAK5 is not only regulated by external K+ conditions but it is also regulated by internal K+ levels, which is in agreement with recent findings. Additionally, HAK5 plays a major role in the uptake of Cs+ in roots. Therefore, studying Cs+ in roots and having more detailed information about its uptake and translocation in the plant would be valuable. Radioactive tracing experiments revealed not only a reduction in the uptake of 137Cs+ and 42K+in skor mutants compared to wild-type but also a different distribution of 137Cs+ and 42K+ in tissues. In order to gain insight into the translocation, accumulation, and repartitioning of both K+ and Cs+ in plants, long-term treatment and split root experiments were conducted with the stable isotopes 133Cs+ and 85Rb+. Finally, our findings show that the K+ distribution in plant tissues regulates root uptake of K+ and Cs+ similarly, depending on HAK5; however, the translocation and accumulation of the two elements are different.

Cesium Fractionation in Miarolitic Pegmatites: A Reevaluation of K-Feldspar Data

Abstract A review of K-feldspar compositions from miarolitic pegmatites shows that in most pegmatites the pocket K-feldspars are enriched in Rb and Cs relative to exopocket K-feldspar within the same body. Rayleigh modeling of simultaneous crystallization of K-feldspar from a melt and coexisting aqueous solution predicts that the Cs content of K-feldspar falls to nil, which implies that rare-alkali enriched (up to 2190 ppm Cs) pocket K-feldspar must have crystallized from a fluid-undersaturated pegmatite melt. However, most petrologists contend that miarolitic cavities develop after exsolution of an aqueous phase from a pegmatite melt. To investigate the process responsible for the high uptake of Cs and Rb in pocket K-feldspar we determined the rare-alkali content of synthetic K-feldspars that crystallized at 500 °C from a supercritical aqueous fluid in a granitic melt + fluid system. The K/Cs ratio of the synthetic K-feldspar was compared to modeled K/Cs ratios for K-feldspars formed from a water-saturated melt in which the initial Cs concentration (Co) of the melt was identical to the starting glass used in experiments. Our results show that the K/Cs ratios of synthetic K-feldspar are orders of magnitude lower than that predicted using the Rayleigh fractionation model. We attribute the high uptake of Rb and Cs in K-feldspar to kinetic effects associated with rapid crystal growth in an undercooled water-saturated melt. Therefore, we propose that Rb- and Cs-rich K-feldspars that line the pockets of natural miarolitic pegmatites are the products rapid growth in an aqueous fluid that coexists with a highly fractionated residual melt.

Leaching of structural Ca2+ ions from a chalcogenide adsorbent by H+ lifts Cs(I) uptake

Acidic wastewater containing radioactive 137Cs is difficult to treat by selective adsorption. Abundant H+ under acidic conditions damages the structure of adsorbents and competes with Cs+ for adsorption sites. Herein, we designed a novel layered calcium thiostannate (KCaSnS) that contains Ca2+ as a dopant. The dopant Ca2+ ion is metastable and larger than the ions attempted before. The pristine KCaSnS demonstrated a high Cs+ adsorption capacity of 620 mg/g at 8250 mg/L Cs+ solution and pH 2, which is 68% higher than that at pH 5.5 (370 mg/g), a trend opposite to all previous studies. The neutral condition allowed the release of Ca2+ present only in the interlayer (∼20%); whereas the high acidity facilitated the leaching of Ca2+ from the backbone structure (∼80%). The complete structural Ca2+ leaching was made possible only by a synergistic interaction of highly concentrated H+ and Cs+. Doping a large enough ion, such as Ca2+, to accommodate Cs+ into the Sn-S matrix upon its liberation opens a new way of designing high-performance adsorbents.

One-pot synthesis of superparamagnetically modified zeolite chabazite for removal of Cs+ from radioactively contaminated water

Composites of sodium-exchanged zeolite chabazite particles with attached superparamagnetic nanoparticles of Fe3O4 and CoFe2O4 ferrite spinels have been produced using a novel solvothermal route. These have been characterized by a combination of techniques, including powder x-ray diffraction, x-ray fluorescence spectroscopy, vibrating sample magnetometry, and both scanning and transmission electron microscopy. These confirm the nature of the attached nanoparticles, and the microscope images show a good dispersion of nanoparticles with a narrow size range deposited uniformly on the surface of the zeolite particles. The magnetization is of sufficient strength to allow magnetic separation from a solution. Both time and pH dependent Cs uptake experiments show that the magnetized systems are still excellent for the rapid uptake of Cs via an ion exchange process with no reduction in property due to the attached nanoparticles.

Interactions between micaceous minerals weathering and cesium adsorption

The environmental behavior of radioactive cesium (RCs) in contaminated areas is generally governed by soil and sediment components and natural weathering conditions. In this study, desorption tests and spectroscopic approaches were used to explore the interaction between the weathering of micaceous minerals (i.e., biotite and phlogopite) and the adsorption of Cs+ and the critical role of weathering in the environmental behavior of RCs. Results showed that the reaction sequence between weathering and Cs+ adsorption significantly affected the surface species of Cs+ and the structure of biotite and phlogopite. Regardless of whether it occurred before, after, or during Cs+ adsorption, weathering generated more high-affinity adsorption sites, namely, interlayer sites (ITs) and frayed edge sites (FESs), to different extents, and then facilitated the uptake of Cs+ at FESs and ITs on micaceous minerals in a poorly exchangeable state. Cs+ stabilized the micaceous mineral structure once it was absorbed within collapsed interlayers by hindering cation exchange and preventing further destruction during weathering. As important weathering factors, high temperature and Ca2+ content promoted the binding of Cs+ in the interlayers of biotite and phlogopite by enhancing interlayer cation exchange. These findings are beneficial for a better understanding of the environmental behaviors of RCs in the hydrosphere and pedosphere.

Soil fertilisation with 137Cs-contaminated and uncontaminated wood ash as a countermeasure to reduce 137Cs uptake by forest plants

The purpose of present study was to find out whether wood ash with a high pH value and neutralizing capacity reduces 137Cs uptake by forest plants many years after the radionuclide fallout. The effects of one-time point fertilisation with 137Cs-contaminated and uncontaminated wood ash alone or in combination with KCl on 137Cs transfer from soil to young leaves and green shoots of various dwarf shrubs and tree species were examined in a long-term fertilisation experiment (2012–2021) conducted in Bazar mixed forest, around 70 km from Chernobyl nuclear power plant. The results indicated minor effects of soil fertilisation, although there were differences between 137Cs uptake by species and years. Soil amendment with 137Cs-contaminated wood ash generally did not affect 137Cs uptake by young shoots and leaves of plants over the growing season in the first year and only slightly decreased Tag for 137Cs in the following years. The effect of a single application of 137Cs-uncontaminated wood ash on reducing 137Cs uptake by plants was generally negligible. Application of 137Cs-contaminated wood ash in combination with KCl reduced plant 137Cs uptake by about 45%, however, such reduction was only significant in some years for bilberry berries, young leaves and green shoots of lingonberry and alder buckthorn. Thus application of wood ash to 137Cs-contaminated forest soil many years after radionuclide fallout generally does not reduce 137Cs uptake by forest vegetation in a mixed forest ecosystem and this countermeasure should be applied with caution.

Uptake and Translocation of Cesium in Lettuce (Lactuca sativa L.) under Hydroponic Conditions

The uptake of radiocesium (RCs) by plants is key to the assessment of its environmental risk. However, the transfer process of RCs in the water-vegetable system still remains unclear. In this work, the uptake and accumulation processes of Cs+ (0-10 mM) in lettuce were explored under different conditions by using hydroponics. The results showed that the higher exposure concentration of Cs+ could lead to a faster uptake rate and would be beneficial to the uptake and accumulation of Cs+. The uptake of K+ by roots and leaves was inhibited significantly when Cs+ concentration increased, but unapparent for Ca2+ and Mg2+. It was found that the higher K+ and Ca2+ concentration was, the higher inhibition was found for the uptake of Cs+ in root. The uptake of Cs+ leads the decrease of chlorophyll content and brought a negative effect on plant photosynthesis, consequently, a negative effect on lettuce morphology and obvious decrease of biomass and root length. The contents of glutathione (GSH), malondialdehyde (MDA), and root vitality were increasing during the growth following stress of high concentrations of Cs+, which caused stresses on the antioxidant system of lettuce. The enrichment coefficient for Cs+ in leaves was in the range of 8-217. Moreover, the transfer factor was in the range of 0.114-0.828, which suggested that the high Cs+ concentration could enhance the transfer of Cs+ from lettuce root to leaf. This study provides more information on the transfer of RCs from water to food chain, promoting the understanding of the potential risk of RCs.

Doped umbite materials for selective abatement of cesium radionuclides from nuclear waste streams

Sb- and Nb-doped Zr and Sn-umbites have been prepared using hydrothermal synthesis with both high purity and yield. All four materials display excellent removal of Cs+ cations from acidic, neutral, and basic solutions, abating at least 80% of the Cs present. This performance is retained in the presence of competing Na+ cations as well as across the pH range. The most sustained selectivity is observed in acidic media, with evidence of a minor reduction in selectivity under basic conditions. The umbites have successfully been shaped into pellets, introducing macroporosity and retaining the selective uptake of Cs in the presence of excess Na. Through thermal treatment, samples of partially Cs-exchanged umbite can be converted into dense silicate phases where radioactive Cs can be immobilized in a potential wasteform for long term storage. These findings present doped umbites as prospective materials for industrial use with selective abatement properties and capabilities for deployment followed by end of life geological disposal.