Tunable luminescence of silver-exchanged SOD zeolite thermally treated under mild conditions

Silver nanoclusters confined zeolite scaffolds have been considered as a promising luminescent material. Herein, luminescent silver nanoclusters were synthesized by incorporating Ag+ and Cs+ ions into the as-synthesized SOD zeolites...

Electrochemical Removal of Cesium Ions via Capacitive Deionization Using an Ion-Exchange Layer Coated on a Carbon Electrode

This study was conducted to evaluate the feasibility of using electrosorption to remove cesium (Cs+) ions from aqueous solutions using the membrane capacitive deionization (MCDI) process. The electrochemical properties were analyzed using cyclic voltammetry (CV) and impedance spectroscopy (EIS). The activated carbon electrode coated by a polymer layer showed higher specific adsorption capacity (SAC) and removal efficiency of Cs+ than the AC electrode. The effects of potential, flow rate, initial Cs+ concentration, and pH values were investigated to optimize the electrosorption performance. The electrosorption capacity increased with an increase in the applied potential and the concentration of Cs+ in the influent water. The pH value is an important parameter on electrosorption performance. The removal of Cs+ ions was affected by the pH of the influent water because H+ ions acted as competing ions during the electrosorption process. Cs+ was preferentially adsorbed to the electrode in the early stages of adsorption but was later replaced by H+. A higher presence of H+ ions could reduce the adsorption capacity of Cs+ ions. The ion-exchange layer coated AC electrode was shown to be favorable for the removal of Cs+, despite the limited electrosorption ability in a highly acidic solution.

Electrochemical Sensing and Removal of Cesium from Water Using Prussian Blue Nanoparticle-Modified Screen-Printed Electrodes

Selective screening followed by the sensing of cesium radionuclides from contaminated water is a challenging technical issue. In this study, the adsorption functionality of Prussian blue (PB) nanoparticles was utilized for the detection and efficient removal of cesium cations. An efficient PB nanoparticle-modified screen-printed electrode (SPE) in the three-electrode configuration was developed for the electrochemical sensing and removal of Cs+. PB nanoparticles inks were obtained using a facile two-step process that was previously described as suitable for dispensing over freshly prepared screen-printed electrodes. The PB nanoparticle-modified SPE induced a cesium adsorption-dependent chronoamperometric signal based on ion exchange as a function of cesium concentration. This ion exchange, which is reversible and rapid, is associated with electron transfer in the PB nanoparticle-modified SPE. Using this electrochemical adsorption system (EAS) based on chronoamperometry, the maximum adsorption capacity (Qmax) of Cs+ ions in the PB nanoparticle-modified SPE reached up to 325 ± 1 mg·g−1 in a 50 ± 0.5 μM Cs+ solution, with a distribution coefficient (Kd) of 580 ± 5 L·g−1 for Cs+ removal. The cesium concentration-dependent adsorption of PB nanoparticles was also demonstrated by fluorescence spectroscopy based on fluorescence quenching of PB nanoparticles as a function of cesium concentration using a standard fluorophore like fluorescein in a manner analogous to that previously reported for As(III).

The study on preparing absorbent of potassium nickel hexacyanoferrate (II) loaded zeolite for removal of cesium from radioactive waste solutions and stable solidification method for those spent absorbents

The development of cesium selective adsorbent is urgent subject for the decontamination of intermediate and high level water from nuclear facilities especially in nuclear accidents. For the selective adsorption and stable immobilization of radioactive cesium, K-Ni- hexacyanoferrate (II) loaded zeolite (FCzeolite) (synthesized zeolite of Hanoi University of Science and Technology) were prepared by impregnation/precipitation method. The ion exchange equilibrium of Cs+ for composites FC-zeolite was attained within 5 h and estimated to be above 97% in Cs+ 100mg/l solution at pH: 4-10. Ion exchange capacity of Cs+ ions (Qmax) for FC-zeoliteX was reached 158.7 and 98.0 mg/g in pure water and sea water respectively.Those values for FC-zeolite A was 103.1 and 63.7 mg/g. Decontamination factor (DF) of FC-zeolite X for 134Cs was 149.7 và 107.5 in pure water and sea water respectively. Initial radioactivity of 134Cs ion solution infect to decontamination factor. KNiFC-zeolite X after uptaked Cs (CsFC- zeolite X) was solidificated in optimal experimental conditions: Mixing CsFC-zeolite X with additive of Na2B4O7 (5%), temperature calcined 900oC for 2h in air. Solid forms was determined some of parameters: Cs immobilization, mechanical stability, volume reduction after calcination (%) and leaching rate of Cs+ ions in solution.

Bioaccumulation and distribution of 137Cs in tobacco cultivated under hydroponic conditions

Potential of plants to uptake metals from soil solution can be successfully applied for removal of long-lived radionuclides such as radiostrontium 90Sr or radiocaesium 137Cs. This work deals with bioaccumulation of Cs in tobacco plants (Nicotiana tabacum L.) hydroponically grown in diluted Hoagland media (HM) spiked with 137CsCl. Speciation analysis using a program Visual MINTEQ showed, that more than 97% of caesium in HM occurred in the form of Cs+ ions. We found that bioaccumulation of Cs significantly decreased from the value 100% to the value 20% removing of Cs from media after 8 days cultivation of plants with increasing HM concentration. However, the concentration ratio (CR) [Cs]shoot : [Cs]root increased with increasing HM concentration from the value 0.10 to the value 0.85. Bioaccumulation of Cs by tobacco plants significantly decreased with increasing CsCl concentration in media from the value 95% found at concentration of CsCl 10 μmol/dm3 to the value 44% at concentration of CsCl 1 000 μmol/dm3. We did not found visual symptoms of Cs toxicity on plants after 8 days cultivation or significant differences in growth rate or transpiration activity at CsCl concentration up to 0.2 mM. However, at > 0.2 mM CsCl concentration the decrease of growth rate and necrosis of young leaves or die-back of leaves (> 2 mM CsCl) were observed. The CR ([Cs]shoot : [Cs]root) increased with increasing concentration of CsCl (10 – 1 000 μmol/dm3) in media from the value 0.10 to the value 0.40. The obtained data suggest that fast growing plant species with high biomass production like tobacco might be a suitable in phytoextraction or rhizofiltration technologies used for 137Cs removing from environment.

Sorption of Co2+, Zn2+, Cd2+ and Cs+ ions by activated sludge of sewage treatment plant

Sludges are byproducts of sewage treatment process. Land application of sewage sludge is one of the final steps of waste water treatment, but solubilization of toxic metals restricts this method of sludge disposal. In our paper cobalt, zinc, cadmium and cesium sorption by suspension of non-treated activated sewage sludge (14 g/dm3, dry wt.) from waste water spiked with 60CoCl2, 65ZnCl2, 109CdCl2 or 137CsCl were determined in laboratory experiments at 20°C. Activated sludge supplied by the municipal sewage treatment plant in Zeleneč (Trnava region, Slovakia) showed high efficiency to sorb Co2+, Zn2+, Cd2+ and Cs+ ions from waste water pH 6-7. The process can be characterized by the concentration equilibrium (Csolid/Cliquid) typical for sorption processes. Efficiency of the sorption increased in the order Cs < Co < Zn < Cd. Metal sorption process was not inhibited by pretreatment of the sludge with 0.2% formaldehyde or thermal inactivation at 60°C, what confirms that the process was not dependent on metabolic activity of the sludge. Cobalt, zinc, cadmium and cesium were easily removable from the sludge by washing with diluted HCl, EDTA or water solutions of the corresponding metal ions, but with low efficiency by deionized water.

Composite Zn(II) Ferrocyanide/Polyethylenimine Cryogels for Point-of-Use Selective Removal of Cs-137 Radionuclides

The feasibility of several approaches to the fabrication of monolith composite cryogels containing transition-metal ferrocyanides for Cs+ ion uptake has been evaluated. Although in the series of investigated metal ion precursors (Cu(II), Zn(II), Ni(II), and Co(II)), in situ formation of the sorption active phase in polyethyleneimine (PEI) cryogel was feasible only in the case of Zn(II) ferrocyanide, this approach has shown significant advantages over the immobilization of ex situ synthesized ferrocyanide nanoparticles. Nanoparticles of the mixed ferrocyanide Zn1.85K0.33[Fe(CN)6] formed in situ had an average size of 516 ± 146 nm and were homogeneously distributed in the monolith located at the polymer surface rather than embedded in the matrix. The Young modulus of the PEI cryogel increased after modification from 25 to 57 kPa, but composites maintained high permeability to the flow. Sorption of Cs+ ions has been investigated at superficial velocity up to 8 m/h. Steep breakthrough profiles and uptake efficiency of >99.5% until breakthrough point confirmed that a supermacroporous structure of the monolith composite assured good mass transfer, so that intraparticle diffusion was not the limiting stage of sorption kinetics. Application of the rate-constant distribution model (RCD model) to analyze the breakthrough curves of Cs+ sorption allowed the identification of two types of sorption sites with a difference in sorption rate constants of ~1 log unit. Most likely, sorption on “fast” sorption sites was governed by ion exchange between Cs+ ions in solution and K+ ions in the ferrocyanide lattice. Cs-137 radionuclide removal was investigated using the monolith composite columns of various geometries at superficial velocity up to the 6.6 m/h; specific gamma activity was reduced from 265 kBq/L to the background level, showing high potential of these materials for POU application.

Prussian Blue Analogues of A2[Fe(CN)6] (A: Cu2+, Co2+, and Ni2+) and Their Composition-Dependent Sorption Performances towards Cs+, Sr2+, and Co2+

Investigation in radioactive contaminant removal from aqueous solutions has been considered essential upon unexpected nuclear accidents. In this report, we have successfully prepared Prussian blue analogues (PBAs) with different substituted cations (A2[Fe(CN)6] (A: Cu2+, Co2+, and Ni2+)). The synthesized PBAs were characterized and employed for the removal of Cs+, Sr2+, and Co2+ as sorption models, which are commonly found in radioactive waste. Sorption examinations reveal that Cu2[Fe(CN)6] has the highest sorption capacity towards Cs+, Sr2+, and Co2+ compared with those of Co2[Fe(CN)6] and Ni2[Fe(CN)6]. This is mainly attributed to the cation-exchange ability of substituted metal within the framework of PBAs. The sorption mechanism is qualitatively and quantitatively supported by infrared spectroscopy (IR) and total reflection X-ray fluorescence spectroscopy analysis (TXRF). In addition, it was found that Cs+ is adsorbed most effectively by PBAs due to the size matching between Cs+ ions and the channel windows of PBAs. These findings are important for the design of sorbents with suitable ion-exchange capacity and selectivity toward targeted radioactive wastes.