Cs Adsorption Research Articles

Removal of cesium from low-level radioactive wastewaters using magnetic potassium titanium hexacyanoferrate

The rapid development of nuclear energy in China has led to an increase in attention to the treatment of low-level radioactive wastewaters (LLRWs). One of the important contaminants is radioactive Cs. The removal of trace amounts of 134Cs and 137Cs can be achieved by means of a selective adsorption process. One of the possibilities is the application of potassium titanium hexacyanoferrate. In this paper, a novel magnetic potassium titanium hexacyanoferrate (M-PTH) material was prepared. The batch experiments demonstrate a selective adsorption of Cs over a wide pH range from 1 to 10. The co-existing nonradioactive ions can affect the adsorption of Cs. By increasing the Na+ and K+ concentration from 0.001 to 0.1M, the distribution coefficient (Kd) of Cs drops slowly within the ranges of 7.28×104 to 1.10×104mL/g and 1.25×105 to 1.49×104mL/g, respectively. The adsorption isotherm coincides well with the Langmuir model. The thermodynamic study reveals an endothermic and spontaneous process. The kinetic performance follows the pseudo-second-order adsorption model, with intra-particle diffusion as the rate-controlling step. Based on the characteristics of M-PTH, a sequencing batch reactor (SBR) was considered to be suitable for the treatment of LLRWs containing radioactive Cs. Up to a total throughput of 70 batches, the decontamination factor (DF) can be kept at 1000. The volume ratio of treated solution and exhausted adsorbent was almost 7000.

In situ growth of Prussian blue nanocrystal within Fe3+ crosslinking PAA resin for radiocesium highly efficient and rapid separation from water

A new nanocomposite, called FPPB, was prepared by the in situ synthesis of a Prussian blue (PB) nanocrystal within Fe3+ crosslinking poly(acrylic acid) (PAA) resin for the highly efficient and rapid separation of radiocesium from water. The adsorption of Cs+ by FPPB follows the Langmuir and Freundlich isotherm model with distribution coefficients touched 1.15×105mL/g and a good adsorption capacity of 72.47mg/g (pH≈7). FPPB displays high adsorption capacity for Cs+ capture under a wide pH range (4.0–10). The kinetics of Cs+ uptake by FPPB is fast (>90% elimination capacity of relatively low Cs+ concentrations during only 20min of Cs+/FPPB contact) and fit well with the pseudo-second-order kinetic model. This should be attributed to the high dispersion of PB nanoparticles. The adsorption Cs+ from complex solutions containing various competitive cations in large excess was also effective. FPPB is a cost-effective sorbent and could be developed by only stirring using environmental friendly and inexpensive materials at room temperature. Furthermore, the FPPB-Cs+ can be easily retrieved from water with sieve. It is expected that the as-prepared FPPB has extensive applicability in the elimination of radiocesium from nuclear wastewater.

Limitation of adsorptive penetration of cesium into Prussian blue crystallite

The adsorption of cesium (Cs) onto Prussian blue (PB) with different crystallite sizes is investigated to examine the limitations of the adsorptive penetration of Cs+ into PB crystallite. The adsorption of Cs+ onto soluble PB occurs via ion exchange with a charge-compensation cation like K+, which originally resides in the crystalline lattice. The ratio of the compensation cation sites that are replaced by Cs+ after adsorption time of 2 weeks significantly increases with decreasing crystallite size, meaning that the adsorption occurs only near the surface of the crystallite during the adsorption time. The depth of Cs+ penetration after 2 weeks is only within approximately 1–2 nm (or 1–2 units of the crystalline lattice) from the external surface of the crystallite at ambient temperature, regardless of the crystallite size. Hence, the crystallite size is the most important factor governing the adsorption performance.

Caesium incorporation and retention in illite interlayers

Radioactive caesium (chiefly 137Cs) is a major environmental pollutant. The mobility of Cs in temperate soils is primarily controlled by sorption onto clay minerals, particularly the frayed edges of illite interlayers. This paper investigates the adsorption of Cs to illite at the molecular scale, over both the short and long term. Transmission electron microscopy (TEM) images showed that after initial absorption into the frayed edges, Cs migrated into the illite interlayer becoming incorporated within the mineral structure. Caesium initially exchanged with hydrated Ca at the frayed edges, causing them to collapse. This process was irreversible as Cs held in the collapsed interlayers was not exchangeable with Ca. Over the long term Cs did not remain at the edge of the illite crystals, but diffused into the interlayers by exchange with K. Results from extended X-ray absorption fine structure spectroscopy (EXAFS) and density functional theory modelling confirmed that Cs was incorporated into the illite interlayer and revealed its bonding environment.

Preparation and characterization of a novel electrospun ammonium molybdophosphate/polyacrylonitrile nanofiber adsorbent for cesium removal

Adsorption of Cs+ ion from aqueous solution onto a novel electrospun ammonium molybdophosphate/polyacrylonitrile nanofiber adsorbent with variation in AMP content, adsorbent concentration, pH, contact time, initial concentration and temperature was studied. The physicochemical characterization was performed by FTIR, XRD, BET and SEM analyses. Langmuir, Freundlich and Dubinin–Radushkevich models were used for analysis of equilibrium data. Kinetic results showed that the experimental data best fitted the pseudo-second-order kinetic model. The adsorption affinity of metal ions onto adsorbent was in order of Cs+ > Co2+ > Mg2+ > Ca2+ > Sr2+. The adsorbent could be easily regenerated after five cycles of adsorption–desorption.

Molecular Study of Cs and CO 2 Adsorption Sites in Smectite Nanoparticles

The Cs adsorption sites were specifically studied by means of positronium annihilation spectroscopy. Beside the interlayer Cs+ cations, a population of Cs is able to adsorb on the surfaces of open nanospaces A and B with their sizes of ~ 0.3 nm and ~ 0.9 nm, which are formed by inserting one- and two-clay nanosheets into the interlayer spaces. The chemical form for Cs in the open nanospace A is the Cs+ cation, whereas the CsOH compound followed by the Cs2O compound and its corresponding hydrate exists at the two-nanosheet edge site in addition to the Cs+ cations on the surfaces in the open space B. Cs adsorbed on the surfaces of both the open nanospaces A and B is so adhesive that it cannot be removed even by the hydrochloric acid solution of pH 1.0, the open nanospaces A and B thus acting as the specific Cs adsorption site. The characteristic local molecular sites as a clay-nanosheet edge and a wedge-shaped frayed part available in the open spaces A and B are responsible for the specific Cs adsorption. Preliminary results of thermogravimetry and differential thermal analysis (TG-DTA) after CO2 gas flow implied that above-mentioned adsorption sites play an important role in capturing CO2.

Granulous KMS-1/PAN composite for Cs+ removal

A novel KMS-1/PAN composite was successfully fabricated simply by combining KMS-1 with PAN. The KMS-1/PAN combines the efficient, rapid adsorption of Cs+ by KMS-1 with granulation for easy separation after adsorption.

Efficient synthesis of size-controlled open-framework nanoparticles fabricated with a micro-mixer: route to the improvement of Cs adsorption performance

An efficient preparation of size-controlled nanoparticles of an open framework coordination polymer.

Preliminary study on removing Cs+/Sr2+ by activated porous calcium silicate—A by-product from high-alumina fly ash recycling industry

137Cs+/90Sr2+-containing radioactive wastewater is one of the most important problems that the world has been facing with. A by-product, activated porous calcium silicate, is generated at high levels by the pre-desiliconizing and soda-lime-sintering processes for producing Al2O3 from high-alumina fly ash. In order to examine if this by-product could be used as an absorbent for removal of 137Cs+/90Sr2+ from radioactive wastewater, various parameters, such as pH, adsorbent dose, contact time, and initial concentration, were discussed. Results indicated that the equilibrium reached in about 2 hr. Activated porous calcium silicate was highly pH sensitive and able to remove Cs+/Sr2+ in a near-neutral environment. The adsorption equilibrium was best described by Freundlich isotherm equations, and the adsorption of Cs+/Sr2+ was a physical process. The adsorption kinetic data could be better fitted by the pseudo-second-order model, and the adsorption was controlled by multidiffusion. Current study showed that activated porous calcium silicate has a good adsorption of Cs+/Sr2+ for their removal. However, other characteristics, such as selectivity because of coexisting cations, elution and regeneration, thermal stability, and acid resistance, should be discussed carefully before using it in an actual field.Implications:Removing 137Cs+/90Sr2+ from radioactive wastewater is one of the tough issues that has been attracting more and more attention world widely, which is the same as fly ash. For recycling high-alumina fly ash, in which Al is extracted to produce Al2O3, a huge amount of activated porous calcium silicate is generated year by year. In this paper, this by-product was successfully used as an absorbent to remove 137Cs+/90Sr2+ from radioactive wastewater for the first time. Factors that affect the absorbability and the mechanisms were discussed in details, providing a possible choice for disposal of 137Cs+/90Sr2+-containing radioactive wastewater.

Synthesis and characterization of polyaniline-titanium tungstophosphate; Its analytical applications for sorption of Cs+, Co2+, and Eu3+ from waste solutions

Crystalline phases of polyaniline-titanium tungstophosphate composite material were synthesized via sol-gel procedure by incorporating the organic polymer polyaniline into the matrix of an inorganic precipitate of titanium tungstophosphate. The physicochemical properties of this hybrid material were determined using atomic absorption spectrophotometry, CHN elemental analysis, X-ray diffraction and X-ray fluorescence analysis, IR spectroscopy, thermal analysis, and scanning electron microscopy. According to the data obtained, the chemical formula of polyaniline-titanium tungstophosphate can be presented as [(WO3)(TiO2)4(H3PO4)3 + (-C6H4NH-)]·8H2O. The material shows monofunctional ion-exchange characteristic and exhibits enhanced resistance to HNO3, HCl, and alkaline media. The ion-exchange capacity of polyaniline-titanium tungstophosphate for Cs+, Co2+, and Eu3+ ions was found to be 3.63, 1.55, and 1.30 mg-equiv g−1, respectively, exceeding the ion-exchange capacity of other composite and inorganic ion exchangers. The material was found to be highly selective to Eu3+, with the following selectivity series: Eu3+ > Cs+ > Co2+. The thermodynamic functions (ΔG0, ΔS0, and ΔH0) of the adsorption of Cs+, Co2+, and Eu3+ ions onto polyaniline-titanium tungstophosphate were calculated. They show that the overall adsorption process is spontaneous and endothermic.

Analysis of 134Cs and 137Cs distribution in soil of Fukushima prefecture and their specific adsorption on clay minerals

We collected surface soil samples within 60 km from the Fukushima Daiichi Nuclear Power Plants (FDNPP) and analyzed spatial and temporal radiocesium distributions. No large change in vertical distribution pattern of radiocesium has been observed on the samples collected in April 2011 and April 2012 at the same sampling points, suggesting strong adsorption of 134Cs and 137Cs on soil. Cesium is known to be adsorbed specifically on clay minerals in soil. To confirm the specific adsorption of Cs on clay minerals in these samples, we divided the soil into different particle sizes and measured the activity in each size fraction. The activity was highest in the clay fraction (<2 μm) and tended to decrease as the particle size increases. The radiocesium interception potential (RIP), which is defined by the product of the frayed edge sites (FES) capacity and Cs-K selectivity coefficient, was measured using carrier-free 137Cs. No correlation between the value of RIP and the penetration depth of radiocesium was observed, probably suggesting other important physicochemical factors.

Adsorption characteristics of Cs+ on biogenic birnessite

Adsorption of Cs+ on biogenic birnessite was investigated and compared with (ad)sorption of other heavy metals and also with (ad)sorption on chemically synthesized birnessite. The adsorption density of Cs+ on biogenic birnessite was smaller than that on chemically synthesized birnessite; however, the (ad)sorption densities of Co2+ and Ni2+ on biogenic birnessite were larger than on chemically synthesized birnessite. These phenomena can be interpreted by considering the distinctive nano-structure of biogenic birnessite, which is not only poorly crystalline and includes organic matter but also according to EXAFS contains a greater proportion of vacant central metal sites than is found in synthetic birnessite. Adsorbed Cs+ ions on both birnessites were mainly in the form of outer sphere complexes, which cannot easily occupy vacant central metal sites in biogenic birnessite. Biogenic birnessite has a greater specific surface area and more fine pores than synthetic birnessite, but these factors do not necessarily lead to more adsorption sites for Cs+ ions.

Weak protein-cationic co-ion interactions addressed by X-ray crystallography and mass spectrometry.

The adsorption of Rb(+), Cs(+), Mn(2+), Co(2+) and Yb(3+) onto the positively charged hen egg-white lysozyme (HEWL) has been investigated by solving 13 X-ray structures of HEWL crystallized with their chlorides and by applying electrospray ionization mass spectrometry (ESI-MS) first to dissolved protein crystals and then to the protein in buffered salt solutions. The number of bound cations follows the order Cs(+) < Mn(2+) ≃ Co(2+) < Yb(3+) at 293 K. HEWL binds less Rb(+) (qtot = 0.7) than Cs(+) (qtot = 3.9) at 100 K. Crystal flash-cooling drastically increases the binding of Cs(+), but poorly affects that of Yb(3+), suggesting different interactions. The addition of glycerol increases the number of bound Yb(3+) cations, but only slightly increases that of Rb(+). HEWL titrations with the same chlorides, followed by ESI-MS analysis, show that only about 10% of HEWL binds Cs(+) and about 40% binds 1-2 Yb(3+) cations, while the highest binding reaches 60-70% for protein binding 1-3 Mn(2+) or Co(2+) cations. The binding sites identified by X-ray crystallography show that the monovalent Rb(+) and Cs(+) preferentially bind to carbonyl groups, whereas the multivalent Mn(2+), Co(2+) and Yb(3+) interact with carboxylic groups. This work elucidates the basis of the effect of the Hofmeister cation series on protein solubility.

Determination of ¹³⁵Cs and ¹³⁵Cs/¹³⁷Cs atomic ratio in environmental samples by combining ammonium molybdophosphate (AMP)-selective Cs adsorption and ion-exchange chromatographic separation to triple-quadrupole inductively coupled plasma-mass spectrometry.

Since the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011, the activity ratio of (134)Cs/(137)Cs has been widely used as a tracer for contamination source identification. However, because of the short half-life of (134)Cs (2.06 y), this tracer will become unavailable in the near future. This article presents an analytical method for the determination of the long-lived (135)Cs (t(2/1) = 2 × 10(6) y) and the atomic ratio of (135)Cs/(137)Cs, as a promising geochemical tracer, in environmental samples. The analytical method involves ammonium molybdophosphate (AMP)-selective adsorption of Cs and subsequent two-stage ion-exchange chromatographic separation, followed by detection of isolated radiocesium isotopes via triple-quadrupole inductively coupled plasma-mass spectrometry (ICP-MS/MS). The AMP-selective adsorption of Cs and the chromatographic separation system showed high decontamination factors (10(4)-10(5)) for interfering elements, such as Ba, Mo, Sb, and Sn. Using ICP-MS/MS, only selected ions enter the collision/reaction cell to react with N2O, reducing the isobaric interferences ((135)Ba(+) and (137)Ba(+)) and polyatomic interferences ((95) Mo(40)Ar(+), (97) Mo(40)Ar(+), (119)Sn(16)O(+), and (121)Sb(16)O(+)) produced by sample matrix ions. The high abundance sensitivity (10(-9) for the (135)Cs/(133)Cs ratio) provided by ICP-MS/MS allowed reliable analysis of (135)Cs and (137)Cs isotopes with the lowest detection limits ever reported by mass counting methods (0.01 pg mL(-1) and 0.006 pg mL(-1), respectively). The developed analytical method was successfully applied to the determination of (135)Cs and (137)Cs isotopes in environmental samples (soil, litter, and lichen) collected after the FDNPP accident for contamination source identification.

Early construction and operation of the highly contaminated water treatment system in Fukushima Daiichi Nuclear Power Station (II) – dynamic characteristics of KURION media for Cs removal in simulated contaminated water

The kinetic characteristics of the column were necessary property to be understood before actual operation. Hence, a functional small-scale zeolite column system was installed for conducting the experiments to understand decontamination behaviors. Each column has a 2 cm inner diameter and a 12 cm height, and 12 g of zeolite-type media was packed into the column. The column experiments were carried out with Kurion-zeolite, herschelite, at different feed rates of simulated water with different concentrations of Cs and sea salt. As expected from equilibrium ion-exchange isotherms obtained for KURION-herschelite, the adsorption of Cs is hampered by the existence of sea salt ratio. The difference in breakthrough behaviors can be ascribed to the difference in sea salt ratio. Above 1000 bed volumes, the adsorption rate of Cs was the same at a solution velocity of between 14 and 81 cm/min. Under the condition of a 3.4 wt% sea salt ratio, the performance of the media supplied by KURION was in the order surfactant modified zeolite < silver-impregnated engineered herschelite = herschelite (H). This result was suggested to evaluate the performance of KURION media on the actual columns.

Early construction and operation of highly contaminated water treatment system in Fukushima Daiichi Nuclear Power Station (I) – Ion exchange properties of KURION herschelite in simulating contaminated water

To support the design and operation of the decontamination system using KURION media for the treatment of highly contaminated water accumulated in Fukushima Daiichi Nuclear Power Station, Central Research Institute of Electric Power Industry has urgently carried out many kinds of research and development programs to support the operation of the decontamination system using columns filled with three kinds of KURION media (H, AGH and SMZ). Since the contaminated water at Fukushima Daiichi Nuclear Power Station contained seawater and oil, the effects of sea salt and dissolved oil on Cs adsorption behavior were examined closely by batch type. The concentration of sea salt in the solutions was varied between 0.0 and 3.4 wt%. The Cs adsorption capacity of KURION herschelite in seawater decreased to nearly 1/10th of that in pure water, but it was still concluded that herschelite has sufficient adsorption capacity to remove Cs from the contaminated water. The effect of dissolved oil could be ignored because of its low solubility in seawater. Langmuir-type adsorption isotherm equations, which can be applied for estimating Cs adsorption in sea salt containing water, were developed.

Modeling of fixed-bed adsorption of Cs+ and Sr2+ onto clay–iron oxide composite using artificial neural network and constant–pattern wave approach

A low-cost, non-toxic and effective adsorbent constituted by a montmorillonite coated by iron oxides (montmorillonite–iron oxide composite) was prepared to assess its effectiveness in the removal of Cs+ and Sr2+ from aqueous solution. Dynamic adsorption experiments were carried out at room temperature under the effect of various operating parameters such as bed depth Z (5–15 cm), initial cation concentration C0 (2–50 mg L−1) and volumetric flow rate Q (0.5–8 mL min−1). Column performance has been modeled with constant-pattern wave approach combined to the Freundlich isotherm model and artificial neural network (ANN) models. The time, initial cation concentration, bed depth and volumetric flow rate were chosen as the input variables whereas, the outlet concentration Ct was considered as the output variable. The developed network was found to be useful in predicting the breakthrough curves. Experimental data for the used system were well fitted with ANN than the combined constant–pattern wave approach.

Influence of Al fraction on photoemission performance of AlGaN photocathode

To research the photoemission performance of a transmission-mode Al(1-x)Ga(x)N photocathode, Al0.24Ga0.76N and GaN photocathodes with the same structure were activated, their spectral responses were measured using a multi-information measurement system at room temperature, and the photocathode parameters were obtained by fitting quantum efficiency curves. The results showed that both the reflective-mode and transmission-mode spectral responses of the AlGaN photocathode were lower than those of the GaN photocathode. Compared with the GaN photocathode, the short-wavelength spectral response of the Al0.24Ga0.76N photocathode was less seriously affected by lattice defects between the buffer and emission layers. The Al atom at the AlGaN photocathode surface could affect the optimal Cs adsorption position, which mainly affects the surface electron escape probability of the photocathode.

Kinetics and competitive modeling of cesium biosorption onto iron(III) hexacyanoferrate modified pine cone powder

This study looked at incorporation of iron(III) hexacyanoferrate onto chemically treated pine cone via iron(III) surface loading and its application for cesium (Cs) adsorption in the presence of alkali/alkali earth metals. The optimum iron(III) loading concentration was 2.50 mol l−1 at pH 7, while optimum hexacyanoferrate (HCF) loading was achieved at a hexacyanoferrate concentration of 0.26 mol l−1. The best-fitting kinetic model was confirmed using the closeness of the predicted equilibrium capacities to the experimentally determined capacity, three error determination methods, and the comparative plots of predictive and experimental uptake of Cs with time. The adsorption rate constants were reduced by alkali/alkali metal addition and the reduction was higher in the HCF-modified pine. The mechanism of Cs adsorption onto raw pine followed the pseudo-second-order model and involved stripping of the hydration water from the metal ion. The presence of Na+ did not alter the adsorption mechanism but Ca2+ addition changed the best-fitting model to pseudo-first-order. The diffusion-chemisorption model best fitted Cs adsorption onto HCF-modified pine and involved adsorption of Cs in its hydrated form, which migrated easily through the zeolite-like lattice of hexacyanoferrate. Addition of Na+ and Ca2+ changed the best-fitting model to a pseudo-first-order model.

Development of Low Cost Adsorbents from Agricultural Waste Biomass for the Removal of Sr(II) and Cs(I) from Water

For the purpose of remediating aquatic environment polluted by radioactive elements such as Cs(I) and Sr(II), two types of adsorption gels were developed using biomass wastes as feed materials: a Ca-type pectin based cation exchanger for the removal of Sr(II) prepared from orange waste and a polyphenol enriched bio-sorbent for Cs(I) prepared from tea leaves. The former was prepared by means of saponification of the methyl ester portion of orange pectin in orange juice residue using lime water. Due to the chemical similarity of Ca(II) and Sr(II), the Ca(II) ions in the saponified orange juice residue (SOJR) are easily replaced by Sr(II) during adsorption. The latter was synthesized by means of cross-linking condensation reaction with concentrated H2SO4. The adsorption of Sr(II) and Cs(I) increased with increasing pH of the solution, suggesting that these metal ions were adsorbed onto active sites of these bio-sorbents through a cation exchange mechanism. These modified biomass adsorbents were found to exhibit high adsorption capacities and fast adsorption rates for the tested metal ions. That is, the adsorption capacity of SOJR for Sr(II) was evaluated as 0.83 mmol/g whereas that obtained for the cross linked tea leaves (CTL) gel with regards to Cs was 1.22 mmol/g. In comparison to the adsorption capacities of other adsorbents, it was concluded that the SOJR and CTL displayed excellent potential for the adsorption of Sr(II) and Cs(I), respectively. Thus, the combined uses of SOJR and CTL gels can be expected to work as a promising alternative to remove radioactive Sr(II) and Cs(I) from polluted water.