Adsorbent For Cs Research Articles

The adsorption of cesium by sulfonic acid functionalized hollow mesoporous silica microspheres

With the development of nuclear industry, radioactive elements such as 137Cs put a threat on the water environment. It is a challenging task to remove the Cs+ in the nuclear wastewater. In the current study, we prepared a new Cs+-adsorbing material by introducing sulfhydryl group onto the surface of hollow mesoporous silica microspheres, then oxidizing the sulfhydryl group to sulfonic acid group. The obtained HMSS-SO3H material had an excellent adsorption capacity for Cs+ in the aqueous solution, with an adsorption capacity of 51.53 mg g−1 in 30 min. Characterization approaches, such as FT-IR and EDS, were used to confirm the result of modification. Adsorption experiments were carried out under. The influence of various parameters on the adsorption process was investigated under the conditions of changing pH, temperature, and time. The effect of competitive ions was also explored. The results indicated that the adsorption process followed the pseudo-second-order model and the main adsorption mechanisms are electrostatic interaction and coordination. The material had a best adsorption performance at a neutral pH. The adsorption process could well-fit the Langmuir's model, with a theoretical maximum adsorption capacity of 81.31 mg g−1. And the adsorption capacity was slightly affected by competing ions such as Mg2+ and Ca2+. The results indicate that the HMSS-SO3H prepared in this study is a promising adsorbent for Cs+, with the advantages of high adsorption capacity, fast adsorption rate and high selectivity.

Fabrication of graphene oxide/ammonium molybdophosphate composite membrane for decontamination of cesium ions from seawater

Efficient separation of radioactive cesium ions (Cs+) from complicated aqueous environmental media has attracted considerable interest, especially seawater. Ammonium molybdophosphate (AMP) is regarded as a promising adsorbent for Cs+, but its fine powder dramatically inhibits the potential for practical applications. Herein, graphene oxide (GO) was utilized as a support for the in-situ growth of AMP, and after vacuum filtration, GO/AMP composite membrane was successfully fabricated. It was found that the GO/AMP membrane exhibited excellent adsorptive filtration performance (47.3 L m−2h−1 bar−1 water flux and 99.2 % rejection for Cs+ with 20 ppm initial concentration, 30 mL feed solution). Influent pH and coexisting metallic ions had scarcely effects on Cs+ rejection. Over five cycles, the water permeability and Cs+ rejection remained essentially unchanged. Moreover, the decontamination of Cs+ from real seawater was demonstrated with the rejection ratio as high as 87.4 % and a relatively inhibitory flux of 14 L m−2h−1 bar−1. Based on FT-IR, XPS, and EXAFS analyzes, the rejection of Cs+ was mainly ascribed to the exchange of NH4+ in AMP with Cs+ in solution, and an inner-sphere coordination of Cs+ rather than a weak outer-sphere interaction between hydrated Cs+ ions and adsorbent occurred.

Innovative potassium hexacyanoferrate intercalated into layered double hydroxide adsorbent for efficient cesium removal from seawater

Effective radioactive wastewater treatment technology is essential to ensure the sustainable development of nuclear energy. Here, the potassium ferrocyanide (HCF) intercalating with layered double hydroxide (LDH) (HCF@LDH) was successfully synthesized by coprecipitation method for selective cesium (Cs) removal from seawater. Characteristics of the adsorbent, and adsorption performance under different environmental conditions including Cs+ ion selectivity, and underlying adsorption mechanism were systematically investigated. The experimental results demonstrated that the adsorption capacity of HCF@LDH was 52.08 mg/g and it effectively removed 100 % of Cs+ from up to 200 mg/L Cs solution within 1 h under an optimal pH of 6.0–10.0. Moreover, the adsorbent displayed high selectivity towards Cs+ even in seawater and more than 90 % of Cs+ was removed from seawater and the highest cesium removal capacity from seawater was 44.64 mg/g. Both the Langmuir isotherm model (R2 = 0.997) and the pseudo-second-order kinetic model (R2 = 0.999) provided a good fit for the adsorption data signifying the adsorption process is homogeneous and formed monolayer through chemisorption. Furthermore, the reusability analysis exhibited this adsorbent was recycled and reused for at least 5 cycles without losing its original adsorption performance. The physicochemical analysis of the HCF@LDH proved that K4Fe (CN)6 successfully intercalated onto LDH and cation exchange between K+ and Cs+ played an important role in effective Cs adsorption. More specifically, the interstitial spaces of the hexacyanoferrate crystals facilitate the cation exchange process. The findings of this study demonstrate that HCF@LDH is a unique, highly effective, and selective adsorbent for Cs+ from complex seawater.

Green nanomaterial-based adsorbent for Cs and Pb removal: Synthesis from industrial waste producing high-value products

ABSTRACT The search for a sustainable society makes necessary the reuse of residues contributing to the producing high-value product. Producing new materials with high-added value increases technological development and builds up new applications. The present study aimed to use residue from the alumina industry and coal ash generated in thermal plants in energy production to synthesize zeolite for wastewater treatment to remove Cs and Pb. Two types of nanomaterials were synthesized: zeolite 4A (ZEA) and zeolite sodalite (ZSD). The Cs adsorption efficiency achieved 73% and 9.4% for ZEA and ZSD, respectively, fitting better for Lineweaver-Burk isotherm and both zeolites removed 100% of Pb from synthetic solutions. Results here reported may be used to design novel wastewater treatment systems from nuclear plants and other industrial processes. The present study can contribute to achieving Sustainable Development Goals 9, 11, and 12.

Eco-friendly natural mineral biotite as a cesium adsorbent: Utilizing low-concentration acid and hydrogen peroxide

Biotite, a phyllosilicate mineral, possesses significant potential for cesium (Cs) adsorption owing to its negative surface charge, specific surface area (SSA), and frayed edge sites (FES). Notably, FES are known to play an important role in the adsorption of Cs. The objectives of this study were to investigate the Cs adsorption capacity and behavior of artificially weathered biotite and identify mineralogical characteristics for the development of an eco-friendly geologically-based Cs adsorbent. Through various analyses, it was confirmed that the FES of biotite was mainly formed by mineral structural distortion during artificial weathering. The Cs adsorption capacity is improved by approximately 39% (from 20.53 to 28.63 mg g−1) when FES are formed in biotite through artificial weathering using a low-concentration acidic solution mixed with hydrogen peroxide (H2O2). Especially, the Cs selectivity in Cs-containing seawater, including high concentrations of cations and organic matter, was significantly enhanced from 203.2 to 1707.6 mL g−1, an increase in removal efficiency from 49.5 to 89.2%. These results indicate that FES of artificially weathered biotite play an essential role in Cs adsorption. Therefore, this simple and economical weathering method, which uses a low-concentration acidic solution mixed with H2O2, can be applied to natural minerals for use as Cs adsorbents.

“Knitted” tetrabenzo-24-crown-8 ether sulfonate as reusable and practical hydrophilic adsorbent for aqueous Cs+ sequestration

Herein, “knitted” tetrabenzo-24-crown-8 ether sulfonate (X-S-TB24CE8) was prepared to afford a practical hydrophilic Cs+ adsorbent. Cyclic TB24CE8 ligands were hyper-crosslinked with dimethoxymethane in the presence of Cs+ template followed by sulfonation to introduce -SO3- groups. Thorough characterization of X-S-TB24CE8 using FTIR, TGA, EA, N2 adsorption/desorption, DLS, XPS, and SEM-EDX confirms its hydrophilic nature and thermal stability. It possesses a granulated porous structure that can be easily recovered by filtration. Removal of Cs+ by X-S-TB24CE8 involves a 1:1:2 TB24CE8:Cs+:SO3- coordination with additional Cs+···SO3- interaction from free sulfonate groups. The Cs+ adsorption follows the Sips isotherm model (Qmax = 233.07 mg g−1) and pseudo-second order kinetics (k2 = 2.63 × 10−3 g mg−1 min−1). In seawater containing Cs+, X-S-TB24CE8 exhibits a strong preference for Cs+ over Na+ (αNa+Cs+= 483), K+ (αK+Cs+= 76), Mg2+ (αMg2+Cs+= 66), and Ca2+ (αCa2+Cs+= 35). X-S-TB24CE8 demonstrated consistent adsorption/desorption performance without undergoing any physical or chemical decomposition. These findings indicate that X-S-TB24CE8 holds significant potential as a competitive and practical adsorbent for Cs+ sequestration.

Preparation of nano-scale ferric hexacyanoferrate using coal ash by microwave-assisted hydrothermal process for cesium removal

The removal of radioactive cesium (Cs+) has received considerable attention owing to its chemotoxicity and radiotoxicity. This study presents a method for producing ferric hexacyanoferrate nanoparticles (Prussian blue, PB), using recycled magnetic coal ash (M-CA) as an effective and selective adsorbent for Cs+ removal. A microwave-assisted hydrothermal technique was employed to recover the Fe solution from M-CA and a simple sol–gel technique was used to synthesize PB nanoparticles. The PB nanoparticles exhibited cubic cluster structures with an average size of 20.67 nm. Their Cs+ adsorption capacity reached 213.061 mg/g, significantly surpassing the capacities of absorbents reported in previous studies. Cs+ was observed to be associated with localized adsorption sites on the PB surfaces, with minimal internal diffusion. In addition, the hydrated radius of Cs+ emerged as a critical factor influencing its adsorption onto PB surfaces, enabling the efficient removal of Cs+ even in the presence of competing ions. These findings offer valuable insights for the straightforward synthesis of highly efficient and selective adsorbents for radioactive substances, as well as the recovery of valuable materials from industrial solid waste.

Highly efficient removal of Cs(I) using the magnetically separable potassium ferrocyanide: Mechanism, economic analysis, and impact insights

Cs nuclides, originating from nuclear weapon tests or compromised nuclear power plants are highly mobile and easily migrate among environmental media, eventually bio-accumulating in the human body and causing serious disease. Reliable and highly efficient removal of Cs(I) ions from radioactive wastewater is of great importance. Herein, a novel magnetic potassium ferrocyanide nanocomposite, viz. K4Fe(CN)6@Fe3O4, was rationally designed for Cs(I) removal. Through a well-controlled in-situ growth method, potassium ferrocyanide [K4Fe(CN)6, KFC] nanocrystals were in-situ grown onto the surface of Fe3O4 nanospheres forming KFC@Fe3O4 nanocomposite. The Cs(I) removal rate of KFC@Fe3O4 can reach over 95% within a relatively short time. Even in the presence of considerable amounts of Na+, Ca2+ and NH4+ ions, KFC@Fe3O4 maintained a considerably high removal rate. KFC@Fe3O4 yielded a relatively lager saturation magnetization value, enabling its rapid separation from the reaction system by introducing an external magnetic field. Notably the embedded potassium in KFC@Fe3O4 plays a vital role in Cs(I) exchange process. The experimental results underscore the superior performance of KFC@Fe3O4 as a potential Cs(I) adsorbent in wastewater. The implications of this study reach extend beyond mere technological advancements, highlighting that the application of this novel methodology for nuclear wastewater treatment requires the engagement of a broad spectrum of potential users. Overall, this study elucidated the mechanism of Cs(I) removal by KFC@Fe3O4, ad developed an eco-friendly and cost-effective strategy for radioactive wastewater purification, while deliberating on the advantages and potential challenges of scaling up the material and process for future application.

Open-framework hybrid zinc/tin selenide as an ultrafast adsorbent for Cs+, Ba2+, Co2+, and Ni2+

Efficient adsorption of radioactive 137Cs+ and 60Co2+ and their decay products 137Ba2+ and 60Ni2+ bears significance for hazard elimination in case of nuclear emergency, which relies on the adsorption rate enhancement that takes advantages of compositional and structural optimization. Herein, we report a zinc-doped selenidostannate constructed from T2-supertetrahedral clusters, namely K3.4(CH3NH3)0.45(NH4)0.15Zn2Sn3Se10·3.4 H2O (ZnSnSe‐1K). The soft Se and micro-porosity synergistically endow this material with a binding affinity to Cs+, Ba2+, Co2+, and Ni2+ ions and ultrafast kinetics with R > 97.6% in 2–60 min. In particular, ZnSnSe‐1K can remove 99.34% of Cs+ in 2 min (KdCs > 1.5 × 105 mL g−1), contributing to a record rate constant k2 of 9.240 g mg−1 min−1 that surpasses all metal chalcogenide adsorbents. ZnSnSe‐1K exhibits good acid/base tolerance (pH = 0–12), and the adsorption capacities at neutral are 253.61 ± 9.15, 108.94 ± 25.32, 45.76 ± 14.19 and 38.49 ± 2.99 mg g−1 for Cs+, Ba2+, Co2+, and Ni2+, respectively. The adsorption performances resist well co-existing cations and anions, and the removal rates can keep above or close to 90% even in sea water. ZnSnSe‐1K is employed in continuous column and membrane filtration, both of which shows excellent elimination efficiency (R > 99%) for mixed Cs+, Ba2+, Co2+, and Ni2+. Especially, the membrane with an ultrathin (70 µm) ZnSnSe‐1K layer can remove 97–100% Cs+ in suction filtration with a short contact time of 0.33 s. Combined with the simple synthesis, facile elution and great irradiation resistance, ZnSnSe‐1K emerges as a selenide adsorbent candidate for use in environmental remediation especially that involving nuclear waste disposal.

Experimental and Theoretical Study of Methylene Blue Adsorption on a New Raw Material, Cynara scolymus—A Statistical Physics Assessment

Methylene blue (MB) adsorption was performed on a natural material powder of Cynara scolymus as a new inexpensive adsorbent identified by Cs. To analyze the Cs material, FTIR, SEM, isoelectric point (pHpzc) analysis, TGA, and DRX were used. The maximum experimental adsorption capacity of the Cs material was 203.333, 192.187, and 179.380 mg•g−1 at 298, 303, and 313 K, respectively. The correlation coefficients (R2) and average percentage errors APE (%) values for the kinetic and isotherms models indicated that the adsorption kinetics followed a pseudo-nth order model and that the traditional isotherm model Redlich–Peterson (R–P) correctly described the experimental data obtained at 298, 303, and 313 K, respectively. The steric, energetic, and thermodynamic characteristics of the most relevant advanced model (double-energy single-layer model (AM 2)) were analyzed in detail. The number of active sites for the first receptors (n1) was determined to be 0.129, 0.610, and 6.833, whereas the number of second active sites (n2) was determined to be 1.444, 1.675, and 2.036 at 298, 303, and 313 K, respectively. This indicated the presence of both multi–docking and multimolecular modes for the first style of MB ions (n1), while only a multimolecular mode for the second style of MB ions (n2). Thermodynamic characteristics demonstrated that MB adsorption onto the Cs adsorbent is spontaneous and feasible.

Cesium ion removal from low-level radioactive wastewater utilizing synthesized cobalt hexacyanoferrate-sand composite

Abstract Here, a novel method of synthesis of a sand-based adsorbent for radioactive Cs+ ion removal is reported. Natural sand has been modified with cobalt hexacyanoferrate (CoHCF) using a simple and effective approach. The detailed physical–chemical characterization of the synthesized adsorbent is carried out using XRD, XPS, UV-visible, FT-IR, ICP-AES and Raman spectroscopy. Cs+ ion batch adsorption studies were conducted radio-analytically, and the sorbent’s adsorption capability was observed to be ∼5 mg g−1. The batch studies revealed that Cs+ ion was selectively adsorbed throughout a broad pH range of 1–10. The rate-controlling steps in the adsorption process, according to kinetic studies, are film diffusion and intraparticular diffusion and the adsorption process follows a second-order kinetics.

Readily regenerated porous fiber-supported metal tin sulfide for rapid and selective removal of cesium from wastewater

The removal of Cs from radioactive wastewater remains a great challenge due to the presence of a large number of coexisting ions. Herein, a novel porous fiber-supported metal tin sulfide named PVC-[Me2NH2]2Sn3S7 was designed. Specifically, four tin sulfides were prepared by the one-pot method in different solvents. Water was the most suitable solvent since it was essential for converting amides to cations. When three amides were used as precursors, [Me2NH2]2Sn3S7 prepared with DMF showed the best adsorption performance. Five polymers were then comprehensively evaluated around physicochemical stability, hydrophilicity, and cost to facilitate the engineering application of adsorbents. Finally, polyvinyl chloride (PVC) was selected as the support material. The optimized porous PVC-[Me2NH2]2Sn3S7 fiber with 50 wt% [Me2NH2]2Sn3S7 percentage can reach adsorption equilibrium within 30 min, has a wide active pH range of 2–12, and has a high adsorption capacity of 419.01 mg g−1. When applied to simulated wastewater, the separation coefficients of Cs+ and coexisting ions were above 1 × 104. The Cs + adsorption enthalpy change was obtained by calorimetric study and simulation calculation. Even after 50 consecutive cycles, the removal efficiency barely decayed. The Cs+ concentration could be enriched to 259.93 times that of the geothermal water. The above advantages make PVC-[Me2NH2]2Sn3S7 a promising adsorbent for selective Cs + removal from wastewater.

Collectable adsorbent based on the adsorption characteristics of sodium citrate-pretreated vermiculite for cesium ion in an aquatic environment

This study aimed to develop a collectable adsorbent for Cs using clay mineral and alginate gel. The adsorption capacity of vermiculite (Verm) for Cs increased from 97.1 mg/g to 119 mg/g after sodium citric treatment. The Verm used in this study has a partial chlorite structure, and the existence of interlayer material was considered. The adsorption sites of Verm for Cs increased because the interlayer material in the partly chlorite structure was removed via sodium citric treatment. The Langmuir adsorption isotherm described this adsorption phenomenon well, indicating that the adsorption of Cs by Verm after sodium citric treatment (Verm-Cit) is monolayer adsorption. Since a typical phenomenon was also observed in which the basal spacing became approximately 1.0 nm when Cs was adsorbed by the interlayer of vermiculite, the interlayer of Verm-Cit functioned as an adsorption site. Verm-Cit was encapsulated in alginate gel beads (AG-Verm-Cit) for accessible collection after adsorption. Although the equilibrium adsorption time of AG-Verm-Cit was extended from 10 min without encapsulation (Verm-Cit) to over 360 min, an adsorption capacity of 60.5 mg/g was obtained even after 30 min. The developed adsorbent requires time to reach equilibrium; however, the adsorption capacity was similar to or higher than reported in previous studies, even with a relatively shorter contact time. Additionally, the weight and volume of the adsorbent encapsulated in alginate gel beads can be decreased by air drying without heat. These properties can contribute to removing Cs from the aquatic environment and to the stable management of adsorbents with radionuclides.

1-aza-18-crown-6 ether tailored graphene oxide for Cs(I) removal from wastewater

Abstract Due to the relative abundance, long half-life and high mobility of radioactive cesium (Cs), new adsorbents are urgently needed to treat Cs to ensure public health. In this study, a graphene oxide (GO) based adsorbent for Cs(I) adsorption was prepared by 1-aza-18-crown-6 ether modification. XRD, FT-IR, XPS and SEM results showed that the properties of 1-aza-18-crown 6 ether modified GO (18C6-GO) changed dramatically compared with that of raw graphite. The adsorption properties of 18C6-GO for Cs(I) were studied by batch static adsorption experiments. The results showed that the adsorption equilibrium time of 18C6-GO was 20 h. Kinetic study revealed that the adsorption rate of Cs(I) conformed to pseudo-second-order kinetic model. Langmuir adsorption isotherm simulation indicated that the adsorption arises at homogeneous adsorption sites on 18C6-GO. Therefore, crown ether modified GO may have implications for the treatment of wastewater.

Adsorptive Removal of Radioactive Cesium from Model Nuclear Wastewater over Hydroxyl-Functionalized Mxene Ti3C2Tx

Selective removal of 137Cs from nuclear wastewater is still a challenge due to the issues of efficient adsorbent exploitation and high concentrations of competitive ions. In this study, two-dimensional-layered Mxene Ti3C2Tx achieved the surface alkaline modification with KOH to be used as an efficient adsorbent for Cs+ removal from model wastewater. Hydroxyl-modified Ti3C2Tx obtained improved the delamination morphology and surface structure compared with the pristine Ti3C2Tx. In addition, the F species in Ti3C2Tx were efficiently removed and the hydroxyl groups were increased after modification. The adsorption efficiency of Cs+ over the hydroxyl-modified Ti3C2Tx was significantly enhanced, being attributed to the improvements in morphology, structure, and properties. 0.05 g of an optimal adsorbent achieved 90% removal of Cs+ with 5 mg·L–1 initial concentration in 50 mL of model wastewater within 5 min at ambient temperature and neutral conditions. Hydroxyl-modified Ti3C2Tx also exhibited high adsorption selectivity for Cs+ in the presence of competitive metal ions such as K+, Na+, Mg2+, and Ca2+. The mechanism study revealed that the ion exchange between [Ti–O]−H+/Cs+ mainly contributed to Cs+ adsorption, and the complexation between the oxygen-containing groups [Ti–O] in modified Ti3C2Tx and Cs was also involved. The hydroxyl-modified Ti3C2Tx was easy to regenerate and exhibited good recyclability for Cs+ adsorption.

Hydrogen ion scattering from alkali/graphene surface: Alkali core states effects

We present a theoretical study of the frontal collision of protons with a graphene surface to which an alkali-adatom is added. Na and Cs adsorbates are studied in a low coverage limit. We analyze how the presence of adsorbates affects the charge exchange when the binary collision between the H+ protons and the adatoms or different carbon atoms close to the impurity occurs. The charge transfer process in the scattering of protons in the K and C atoms of a graphene surface to which a K adatom is added has already been analyzed and discussed in our previous works. We find that the inner states of the alkali atoms adsorbed on graphene introduce important differences in the charge transfer depending on their positions with respect to the valence band of graphene. For a better grasp of this, in this work we select Cs and Na as adatoms due to Cs has core levels that can resonate with the valence band of graphene, while Na does not. The interacting system is described by the Anderson Hamiltonian which takes into account the electronic repulsion at the projectile site; the ion charge fractions after the collision are calculated by using the non-equilibrium Green-Keldysh functions formalism. Also, we describe the adsorption of the alkali atom on the surface using the single impurity Anderson model and introduce the Green's functions required to calculate the adatom spectral density. In the scattering of H+ from Cs, the charge fractions as a function of the incident energy, behave similarly to the scattering from K. For the Na adatom, the dependence is different, showing a monotonous increase in the high energy regime. The results of this work allow us to infer the signals in the charge exchange, from the localized features of the density of states on the alkaline adsorbate during the scattering process, due to the peculiarities of the electronic band structure of graphene.

Study on stable solidification of silica-based ammonium molybdophosphate adsorbing cesium: Micromechanics and density functional theory modeling

Silica-based ammonium molybdophosphate (AMP/SiO2) adsorbent can effectively remove 137Cs from simulated wastewater discharged during the Fukushima NPP-1 accident. A pressing/sintering method for the final disposal of the spent Cs adsorbent was described herein. Immobilization of Cs in the stable ceramic solid form of Cs4Al4Si20O48 was accomplished using natural mordenite. Different sintering temperatures and duration times exerted different effects on the final microstructures and the mechanical and loading abilities of the solidified products. At the sintering condition of 1 h duration time at 1,200 °C, the Cs immobilization ratio was almost 100%, and a relatively high hardness and elastic modulus of 3.50 and 35.38 GPa, respectively, were achieved. The formation of crystals as temperature increased corresponded to the micromechanical properties of the sintered product. Density functional theory calculations revealed that Cs4Al4Si20O48 is orthogonal with cubic unit cells, and Cs–O is more likely to form an ionic bond in the crystal. The dissolution of ceramic matrix was determined to be a temperature-dependent solidification mechanism that involves a corrosion medium. These findings provide a basic technological support for the stabilization of radioactive wastes.

Effective cesium removal from Cs-containing water using chemically activated opaline mudstone mainly composed of opal-cristobalite/tridymite (opal-CT)

Opaline mudstone (OM) composed of opal-CT (SiO2·nH2O) has high potential use as a cesium (Cs) adsorbent, due to its high specific surface area (SSA). The objective of this study was to investigate the Cs adsorption capacity of chemically activated OM and the adsorption mechanism based on its physico-chemical properties. We used acid- and base-activation methods for the surface modification of OM. Both acid- and base- activations highly increased the specific surface area (SSA) of OM, however, the base-activation decreased the zeta potential value more (− 16.67 mV), compared to the effects of acid-activation (− 6.60 mV) or non-activation method (− 6.66 mV). Base-activated OM showed higher Cs adsorption capacity (32.14 mg/g) than the others (acid: 12.22 mg/g, non: 15.47 mg/g). These results indicate that base-activation generates pH-dependent negative charge, which facilitates Cs adsorption via electrostatic attraction. In terms of the dynamic atomic behavior, Cs cation adsorbed on the OM mainly exist in the form of inner-sphere complexes (IS) containing minor amounts of water molecules. Consequently, the OM can be used as an effective Cs adsorbent via base-activation as an economical and simple modification method.

Cesium removal from a water system using a polysulfone carrier containing nitric acid-treated bamboo charcoal

Laboratory scale sorption and desorption experiments were performed to investigate the cesium (Cs) removal efficiency of a bead-shaped polysulfone carrier containing HNO3-treated bamboo charcoal (BC). The average Cs removal efficiency of BC only and of polysulfone carrier without BC after 1 h sorption reaction was 53 and 18%, respectively. However, the Cs removal efficiency for the polysulfone carrier with 5% HNO3-treated BC (P-5N-BC) after 1 h and 24 h reaction was 66 and 98%, respectively. The Cs removal efficiency after 24 h reaction remained >85% over a wide range of pH and temperature conditions, suggesting that using P-5N-BC as the Cs adsorbent is feasible in a variety of aquatic environments. The maximum Cs sorption capacity (qm) of P-5N-BC, as calculated from a Langmuir isotherm model, was 60.9 mg/g, which is much higher than those of other adsorbents from previous studies for 1 h of sorption time. The Cs desorption rate of P-5N-BC for 24 h desorption time was <17%, showing that the Cs was stably enough attached to the HNO3-treated BC for long-term use. The results of continuous column experiments showed that the total amount of treated water from the column packed with P-5N-BC increased more than nine times when compared with that from the only BC-granule-packed column. The P-5N-BC maintained more than 68% Cs removal efficiency after 90 pore volumes of flushing, suggesting that only 15 g of P-5N-BC (with only 0.75 g of HNO3-treated BC) could clean 5 L of Cs-contaminated water (initial Cs concentration: 1.0 mg/L; effluent concentration: < 0.09 mg/L). The present results demonstrate that P-5N-BC has remarkable potential for removal of Cs from diverse water systems.

Removal of Cs+ in water by dibenzo-18-crown-6 ether tethered on mesoporous SBA-15 as a reusable and efficient adsorbent

Inadvertent release of radioactive Cs+ to the environment poses a grave threat as it may cause severe health problems to the exposed population. One of the practical solutions is to use effective regenerable Cs+ adsorbents to minimize total waste volume. In this study, a mesoporous adsorbent for Cs+ capture was prepared by tethering a Cs+-selective ligand monoamino-dibenzo-18-crown-6 (MA-DB18C6) ether on chloro-functionalized SBA-15 (Cl-SBA) support. The dispersible adsorbent (DB18C6-SBA) registered a maximum adsorption capacity of 94.54 mg g−1 from non-linear Hill isotherm fitting. The model suggests near Langmuir-type of Cs+ capture as Hill coefficient nH→1. This indicates nearly independent monolayer Cs+ binding with the tethered DB18C6 with no adsorbate interaction. Kinetic study reveals a pseudo-second order of Cs+ uptake rate while thermodynamic analyses show the spontaneity and endothermicity of the process. Compared with conventional ligand impregnation technique, covalently tethered DB18C6 occupy smaller surface space of SBA-15 resulting in higher ligand loading and higher adsorption capacity. DB18C6-SBA is regenerable in mild acid and exhibits consistent adsorption capacity after several reuse cycles. It can selectively capture Cs+ from simulated high level liquid waste, but more effectively from Cs+-contaminated surface water with KD ∼ 1578 mL g−1 and concentration factor CF ∼ 2267 in the presence of Na+, K+, Mg2+ and Ca2+. Cycled batch adsorption shows that DB18C6-SBA can be reused with consistent uptake performance while lab-scale sequential adsorption-nanofiltration system with Cs+ stripping further demonstrates its potential long-term use as Cs+ adsorbent for the treatment of contaminated water.