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1.
J Environ Sci (China) ; 143: 126-137, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-38644011

RESUMO

Radioisotope leaking from nuclear waste has become an intractable problem due to its gamma radiation and strong water solubility. In this work, a novel porous ZnFC-PA/PSF composite sphere was fabricated by immobilization of ferrocyanides modified zinc phytate into polysulfone (PSF) substrate for the treatment of Cs-contaminated water. The maximum adsorption capacity of ZnFC-PA/PSF was 305.38 mg/g, and the removal efficiency of Cs+ was reached 94.27% within 2 hr. The ZnFC-PA/PSF presented favorable stability with negligible dissolution loss of Zn2+ and Fe2+ (< 2%). The ZnFC-PA/PSF achieved high-selectivity towards Cs+ (Kd = 2.24×104 mL/g) even in actual geothermal water. The adsorption mechanism was inferred to be the ion-exchange between Cs+ and K+. What's more, ZnFC-PA/PSF worked well in the fixed-bed adsorption (E = 91.92%), indicating the application potential for the hazardous Cs+ removal from wastewater.


Assuntos
Poluentes Químicos da Água , Adsorção , Poluentes Químicos da Água/química , Purificação da Água/métodos , Sulfonas/química , Polímeros/química , Porosidade , Césio/química , Eliminação de Resíduos Líquidos/métodos , Zinco/química , Águas Residuárias/química
2.
Environ Sci Pollut Res Int ; 31(17): 25342-25355, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38472574

RESUMO

We investigated the structural changes in clay minerals after Cs adsorption and understood their low desorption efficiency using an ion-exchanger. We focused on the role of interlayers in Cs adsorption and desorption in 2:1 clay minerals, namely illite, hydrobiotite, and montmorillonite, using batch experiments and XRD and EXAFS analyses. The adsorption characteristics of the clay minerals were analyzed using cation exchange capacity (CEC), maximum adsorption isotherms (Qmax), and radiocesium interception potential (RIP) experiments. Although illite showed a low CEC value, it exhibited high selectivity for Cs with a relatively high RIP/CEC ratio. The Cs desorption efficiency after treatment with a NaCl ion exchanger was the highest for illite (74.3%), followed by hydrobiotite (45.5%) and montmorillonite (30.3%); thus, Cs adsorbed onto planar sites, rather than on interlayers or frayed edge sites (FESs), is easily desorbed. After NaCl treatment, XRD analysis showed that the low desorption efficiency was due to the collapse of the interlayer-fixed Cs, which tightly narrowed the interlayers' hydrobiotite due to the ion exchange of divalent cations (Mg2+ or Ca2+) into the monovalent cation (Na+). Moreover, EXAFS analysis showed that hydrobiotite formed inner-sphere structures after NaCl desorption, indicating that it was difficult to remove Cs from NaCl desorption due to the collapsed hydrobiotite and montmorillonite interlayers as well as the strong bonding in FESs of illite. In contrast, chelation desorption using oxalic acid effectively dissolved the narrowed interlayers of hydrobiotite (98%) and montmorillonite (85.26%), enhancing the desorption efficiency. Therefore, low desorption efficiency for Cs clays using an ion exchanger was caused by the collapsed interlayer due to the exchange between monovalent cation and divalent cation.


Assuntos
Bentonita , Césio , Argila , Césio/química , Adsorção , Cloreto de Sódio , Minerais/química , Cátions Monovalentes , Silicatos de Alumínio/química
3.
Chemosphere ; 353: 141570, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38447900

RESUMO

Selective adsorption is the most suitable technique for eliminating trace amounts of 137Cs from various volumes of 137Cs-contaminated water, including seawater. Although various metal ferrocyanide (MFC)-functionalized magnetic adsorbents have been developed for the selective removal of 137Cs and magnetic recovery of adsorbents, their adsorption capacity for Cs remains low. Here, magnetic hierarchical titanium ferrocyanide (mh-TiFC) was synthesized for the first time for enhanced Cs adsorption. Hierarchical TiFC, comprising 2-dimensional TiFC flakes, was synthesized on SiO2-coated magnetic Fe3O4 particles using a sacrificial TiO2 shell as a source of Ti4+ via a reaction with ferrocyanide under acidic conditions. The resultant mh-TiFC exhibited the highest maximum adsorption capacity (434.8 mg g-1) and enhanced Cs selectivity with an excellent Kd value (6,850,000 mL g-1) compared to those of previously reported magnetic Cs adsorbents. This enhancement was attributed to the hierarchical structure, which reduced intracrystalline diffusion and increased the surface area available for direct Cs adsorption. Additionally, mh-TiFC (0.1 g L-1) demonstrated an excellent removal efficiency of 137Cs exceeding 99.85% for groundwater and seawater containing approximately 22 ppt 137Cs. Therefore, mh-TiFC offers promising applications for the treatment of 137Cs-contaminated water.


Assuntos
Radioisótopos de Césio , Césio , Poluentes Químicos da Água , Césio/química , Água/química , Titânio , Ferrocianetos/química , Dióxido de Silício/química , Adsorção , Fenômenos Magnéticos , Poluentes Químicos da Água/análise
4.
Chemosphere ; 353: 141510, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38401861

RESUMO

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.


Assuntos
Silicatos de Alumínio , Césio , Peróxido de Hidrogênio , Césio/química , Minerais/química , Compostos Ferrosos/química , Adsorção
5.
Int J Biol Macromol ; 254(Pt 2): 126864, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37703986

RESUMO

A magnetic micro porous structure composite based on alginate and Prussian blue (M-SA-PB) was simply prepared for cesium removal from the aqueous solutions. The gelation and formation of PB proceeded through the same step, which made the PB homogenously distributed and firmly attached to the alginate matrix. The homogenizer was applied to break down the bulky gel structure into micro-ones, and the lyophilizer will provide the porous structure. Batch cesium sorption experiments showed that the adsorption kinetics and isotherms were attributed to the pseudo-second-order model and Langmuir isotherm. Moreover, the Cs-ion is favorably adsorbed on the M-SA-PB composite surface as a monolayer towards Cs, with a maximum adsorption capacity reach of 191.0 mg/g. Furthermore, the M-SA-PB adsorbent showed excellent adsorption selectivity of Cs from multiple-ion solutions. Our work was extended to use the M-SA-PB composite in dynamic cesium sorption. The column studies showed that the removal efficiency of Cs+ increased with increasing bed depth as well as the initial cesium concentration. Finally, as previously mentioned, the M-SA-PB could be considered an excellent Cs+ scavenger employing both batch and dynamic approaches, which makes it a promising adsorbent for practical investigations.


Assuntos
Césio , Poluentes Químicos da Água , Césio/química , Hidrogéis , Adsorção , Alginatos/química , Cinética , Fenômenos Magnéticos , Poluentes Químicos da Água/química , Concentração de Íons de Hidrogênio
6.
J Environ Radioact ; 272: 107350, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38071796

RESUMO

In this study, microstructural differences and changes in the adsorption capacity of cesium between cement and carbonated cement were investigated. Cement blocks were ground to powder for rapid carbonation, and microscopic variations were characterized by XRF, XRD, FT-IR, SEM, BET, and TGA. The characterization results show that the conversion of Ca(OH)2 and calcium silicate hydrate (C-S-H) gel to CaCO3 in cement after carbonation. And the component of Ca(OH)2 in the powder sample disappeared after three days of rapid carbonation. Batch experiments were used to investigate adsorption under the influence of time, initial cesium concentration, temperature, and ion coexistence. Pseudo-second-order kinetic and Langmuir isothermal model fitting could better describe the adsorption process and the results show that the maximum adsorption capacity of cement after carbonation surges from 29.6 µg‧g-1 to 1.58-5.89 mg‧g-1. (Different carbonating times lead to varying adsorption capacity.) The adsorption capacity decreases with increasing temperature. At temperatures of 293 K and 333 K, the calculated Gibbs free energy change values of cement with different carbonated degrees adsorbing cesium are -10.3 âˆ¼ -14.9 kJ‧mol-1 and -8.03 âˆ¼ -12.4 kJ‧mol-1. And the calculated values of enthalpy change and entropy change are -18.8 âˆ¼ -23.8 kJ‧mol-1 and -27.9 ∼ -37.1 J‧mol-1‧K-1. Combining the characterization and adsorption results, the huge increase in cesium adsorption capacity is closely related to the conversion of Ca(OH)2 to CaCO3, which will provide a new perspective on the adsorption mechanism of cesium in cement.


Assuntos
Monitoramento de Radiação , Poluentes Químicos da Água , Césio/química , Pós , Adsorção , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Carbonatos , Água/química , Cinética , Concentração de Íons de Hidrogênio , Soluções
7.
Int J Mol Sci ; 24(23)2023 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-38069346

RESUMO

Conditioning of radioactive waste generated from the operation of medical institutions, nuclear cycle facilities, and nuclear facilities is important for the safety of the environment. One of the most hazardous radionuclides is radioactive cesium. There is a need for more effective solutions to contain radionuclides, especially cesium (Cs+). Geopolymers are promising inorganic materials that can provide a large active surface area with adjustable porosity and binding capacity. The existence of nanosized zeolite-like structures in aluminosilicate gels was shown earlier. These structures are candidates for immobilizing radioactive cesium (Cs+). However, the mechanisms of their interactions with the aluminosilicate framework related to radionuclide immobilization have not been well studied. In this work, the influence of alkaline cations (Na+ or K+) and the aluminosilicate framework structure on the binding capacity and mechanism of interaction of geopolymers with Cs+ is explored in the example of a sodalite framework. The local structure of the water molecules and alkaline ions in the equilibrium state and its behavior when the Si/Al ratio was changed were studied by DFT.


Assuntos
Silicatos de Alumínio , Césio , Césio/química , Cátions , Radioisótopos
8.
Environ Sci Pollut Res Int ; 30(60): 125526-125539, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37999846

RESUMO

Prussian blue (PB) is widely used for the selective removal of radioactive cesium ions (Cs+) from aqueous solutions. Due to its small size and easy dispersion in water, PB requires a carrier that is both inexpensive and easily separable. Magnetic porous biochar (MPBC) was formed by activating starch with FeCl3 through a one-step calcination method. MPBC can be used as a carrier for Prussian blue, which is easily separated from the solution. This composite material (PB/MPBC) has a rich pore structure and maintains effective surface area, which can facilitate the penetration of Cs+ into the adsorbent. Besides, PB/MPBC exhibits high selectivity and good adsorption capacity achieving a large removal capacity of 101.43 mg/g. Thus, this study provides a novel approach for preparing composites with efficient removal of Cs+.


Assuntos
Césio , Poluentes Químicos da Água , Césio/química , Porosidade , Adsorção , Água , Íons , Poluentes Químicos da Água/química , Fenômenos Magnéticos , Cinética
9.
Environ Sci Process Impacts ; 25(7): 1204-1212, 2023 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-37317925

RESUMO

In this study, we report chemical species of Cs and I in condensed vaporized particles (CVPs) produced by melting experiments using nuclear fuel components containing CsI with concrete. Analyses of CVPs by SEM with EDX showed the formation of many round particles containing Cs and I of diameters less than ∼20 µm. X-ray absorption near-edge-structure and SEM-EDX analyses showed two kinds of particles: one containing large amounts of Cs and I, suggesting the presence of CsI, and the other containing small amounts of Cs and I with large Si content. When CVSs were placed in contact with deionized water, most of the CsI from both particles was dissolved. In contrast, some fractions of Cs remained from the latter particles and possessed different chemical species from CsI. In addition, the remaining Cs was concomitantly present with Si, resembling chemical components in the highly radioactive cesium-rich microparticles (CsMPs) released by nuclear plant accidents into the surrounding environments. These results strongly suggest that Cs was incorporated in CVSs along with Si by melting nuclear fuel components to form sparingly-soluble CVMPs.


Assuntos
Césio , Iodo , Césio/química , Iodo/química , Volatilização , Centrais Nucleares , Liberação Nociva de Radioativos
10.
Environ Sci Pollut Res Int ; 30(18): 53140-53156, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-36853538

RESUMO

Natural zeolite is organically modified with the surfactant cetyltrimethylammonium bromide (CTAB) and employed as a dual-function material for simultaneous adsorption of Cs+ cations and HCrO4- anions from aqueous solutions. Unmodified and modified zeolites are characterized by Fourier transform infrared (FTIR), dynamic light scattering (DLS), nitrogen adsorption-desorption isotherms, and X-ray diffraction (XRD). The results showed that CTAB-zeolite had the efficiency to simultaneously adsorb the concerned species in the pH range 2.5-4.2. The kinetic data showed that 90 and 300 min for Cs(I) and Cr(VI), respectively, were sufficient to attain equilibrium and the data are well-fitted by the double-exponential kinetic model. Of the studied adsorption isotherm models, Redlich-Peterson was the best one for describing the equilibrium adsorption isotherms. Values of ∆H°, ∆S°, and ∆G° for the present adsorption processes are estimated. CTAB-zeolite exhibited adsorption capacities of 0.713 and 1.216 mmol/g for Cs(I) and Cr(VI), respectively, which are comparable with the data reported in the literature. The adsorption mechanism of the concerned (radio)toxicants is proposed.


Assuntos
Poluentes Químicos da Água , Zeolitas , Cromatos , Tensoativos/química , Zeolitas/química , Adsorção , Cetrimônio , Concentração de Íons de Hidrogênio , Ânions , Cinética , Cátions , Césio/química , Poluentes Químicos da Água/análise , Espectroscopia de Infravermelho com Transformada de Fourier
11.
Phys Chem Chem Phys ; 25(3): 1799-1807, 2023 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-36597992

RESUMO

Absorption of sufficiently energetic X-ray photons by a molecular system results in a cascade of ultrafast electronic relaxation processes which leads to a distortion and dissociation of its molecular structure. Here, we demonstrate that only decomposition of powdered cesium oxalate monohydrate induced by monochromatic X-ray irradiation under high pressure leads to the formation of cesium superoxide. Whereas, for an unhydrated form of cesium oxalate subjected to the same extreme conditions, only degradation of the electron density distribution is observed. Moreover, the corresponding model of X-ray induced electronic relaxation cascades with an emphasis on water molecules' critical role is proposed. Our experimental results suggest that the presence of water molecules in initially solid-state systems (i.e. additional electronic relaxation channels) together with applied high pressure (reduced interatomic/intermolecular distance) could potentially be a universal criteria for chemical and structural synthesis of novel compounds via X-ray induced photochemistry.


Assuntos
Césio , Superóxidos , Raios X , Césio/química , Oxalatos , Água
12.
Environ Res ; 221: 115309, 2023 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-36646200

RESUMO

To date, radiocesium (137Cs) has been considered stable in the form of pollucite mineralized through high-temperature heat treatment. This study presented a possibility through experimental results that the entire medium exists as amorphous aluminosilicate at a relatively low temperature, but cesium is partially and preferentially converted from a composite adsorbent into pollucite. Cesium lowers the eutectic point within the system and initiates the nucleation of pollucite prior to other elements. We confirmed that the partial mineral phase of cesium showed the same chemical stability as when the entire medium was converted to pollucite. X-ray absorption spectroscopy provided direct evidence for this phenomenon; also, the stability results of radioactive cesium shown through a series of sintering experiments supported the conclusion. This method can be applied as a method to immobilize radioactive cesium under relatively mild temperature conditions of atmospheric pressure, while eliminating the problem of diffusion due to its volatilization.


Assuntos
Radioisótopos de Césio , Césio , Césio/análise , Césio/química , Silicatos de Alumínio
13.
Environ Sci Pollut Res Int ; 30(1): 1579-1594, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-35918581

RESUMO

Vermiculite and micaceous minerals are relevant Cs+ sorbents in soils and sediments. To understand the bioavailability of Cs+ in soils resulting from multi-cation exchanges, sorption of Cs+ onto clay minerals was performed in batch experiments with solutions containing Ca2+, Mg2+, and K+. A sequence between a vermiculite and various micaceous structures has been carried out by conditioning a vermiculite at various amounts of K. Competing cation exchanges were investigated as function of Cs+ concentration. The contribution of K+ on trace Cs+ desorption is probed by applying different concentrations of K+ on Cs-doped vermiculite and micaceous structures. Cs sorption isotherms at chemical equilibrium were combined with elemental mass balances in solution and structural analyses. Cs+ replaces easily Mg2+  > Ca2+ and competes scarcely with K+. Cs+ is strongly adsorbed on the various matrix, and a K/Cs ratio of about a thousand is required to remobilize Cs+. Cs+ is exchangeable as long as the clay interlayer space remains open to Ca2+. However, an excess of K+, as well as Cs+, in solution leads to the collapse of the interlayer spaces that locks the Cs into the structure. Once K+ and/or Cs+ collapse the interlayer space, the external sorption sites are then particularly involved in Cs sorption. Subsequently, Cs+ preferentially exchanges with Ca2+ rather than Mg2+. Mg2+ is extruded from the interlayer space by Cs+ and K+ adsorption, excluded from short interlayer space and replaced by Ca2+ as Cs+ desorbs.


Assuntos
Silicatos de Alumínio , Potássio , Argila , Silicatos de Alumínio/química , Césio/química , Minerais , Cátions , Solo/química , Adsorção
14.
Environ Sci Pollut Res Int ; 30(13): 36807-36823, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36564688

RESUMO

In this work, novel Prussian blue tetragonal nanorods were prepared by template-free solvothermal methods to remove radionuclide Cs and Sr. The as-prepared Prussian blue nanorods were identified and characterized by scanning electron microscopy, transmission electron microscope, Fourier transform infrared spectroscopic, thermogravimetric analysis, zeta potential, and surface analysis, and its sorption performance was tested by batch experiments. Our results suggest that Prussian blue nanorods exhibited better adsorption performance than co-precipitation PB or Prussian blue analogue composites. Thermodynamic analysis implied that the adsorption process was spontaneous and endothermic which was described well with the Langmuir isotherm and pseudo-second-order equation. The maximum adsorption capacity of PB nanorod was estimated to be 194.26 mg g-1 and 256.62 mg g-1 for Cs+ and Sr2+(adsorbate concentration at 500 mg L-1, the temperature at 298 k, pH at 7.0). Moreover, the experimental results showed that the Prussian blue nanorods have high crystallinity, few crystal defects, and good stability under alkaline conditions. The adsorption mechanism of Cs+ and Sr2+ was studied by X-ray photoelectron spectroscopy, X-ray diffraction, and 57Fe Mössbauer spectroscopy. The results revealed that Cs+ entered the PB crystal to generate a new phase, and most of Sr2+ was trapped in the internal crystal and the other exchanged Fe2+. Furthermore, the effect of co-existing ions and pH on PB adsorption process was also investigated. The results suggest that PB nanorods were an outstanding candidate for removing Cs+ and Sr2+ from radioactive wastewater.


Assuntos
Estrôncio , Poluentes Químicos da Água , Estrôncio/análise , Águas Residuárias , Césio/química , Ferrocianetos/química , Adsorção , Espectroscopia de Infravermelho com Transformada de Fourier , Cinética , Poluentes Químicos da Água/análise
15.
J Chromatogr A ; 1681: 463488, 2022 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-36113337

RESUMO

Bis-octyloxy-calix[4]arene-mono-crown-6 (BOCMC) is a selective ligand for Cs(I) cation, and has been used in solvent extraction method for its separation from acidic feed. Looking at the various advantages and ease of extraction chromatography separation method, an attempt was made to prepare stable composite beads containing BOCMC entrapped in a suitable polymeric matrix. Therefore, an attempt was made to prepare a series of composite polymeric beads containing BOCMC in polysulfone (PS), polyether sulfone (PES) and sodium alginate polymeric matrix. Preparations of the beads were attempted by dissolving the solid BOCMC in the polymer solution, and also by using the ligand solution in isodecanol/dodecane and ionic liquids and then mixing in the polymeric solution. Every attempt failed to get the desired quality of beads in PES and sodium alginate matrix. However, very good quality and stable beads were obtained when 25 mM ligand solution dissolved in C8mim.Tf2N ionic liquid was used in PS matrix. Detail study for the extraction chromatography separation of Cs(I) was studied with BOCMC/C8mim.Tf2N/PS composite beads. Detail investigations on the preparation, characterization, reusability and radiation stability of these beads have been studied and reported in details.


Assuntos
Líquidos Iônicos , Alginatos/química , Calixarenos , Césio/química , Ligantes , Fenóis , Polímeros/química , Sulfonas
16.
Chemosphere ; 308(Pt 2): 136445, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36113663

RESUMO

While nuclear energy with zero carbon emissions will continue to occupy an indispensable position in future scenarios for power generation, the proper disposal of nuclear waste is still highly challenging in many countries. Adsorption is currently one of the primary methods used for removal of cesium from wastewater. However, no available literature has systematically summarized advances and outlooks on the adsorptive removal of cesium, and research issues such as relevant adsorption mechanisms remain largely unexplored. In this study, a bibliometric analysis was used to quantitatively analyze 10141 publications in the Web of Science Core Collection that were published from 1900 to 2022. Current publication trends and active countries, most influential authors and institutions, journal distribution, and research hotspots and trends were reviewed and summarized. The results for the conceptual structure and evolution of investigations in this field showed three distinct periods of rapid development in recent decades. The first period concerned the scope, degree, and influences of pollution by cesium and the development of natural adsorbents. The second period included the exploration and verification of adsorption mechanisms, the fabrication and optimization of new materials, and the application of density functional theory for chemical calculations. The third period involved the development of more advanced biodegradable, nanoscale and synthetic materials with great potential for use as adsorbents as well as advances in engineering applications. Notably, the study showed that it is necessary to further enhance application-driven laboratory investigations. Future directions for research were proposed, such as the investigation of complex adsorption mechanisms, development of new materials, and engineering applications of materials developed in the laboratory. The findings will provide valuable insights and serve as a reference for researchers and policymakers as they address the adsorptive remediation of cases of pollution by cesium.


Assuntos
Resíduos Radioativos , Águas Residuárias , Adsorção , Bibliometria , Carbono , Césio/química , Águas Residuárias/química
17.
Environ Res ; 214(Pt 4): 114072, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-35987372

RESUMO

Radioactive elements released into the environment by accidental discharge constitute serious health hazards to humans and other organisms. In this study, three gasified biochars prepared from feedstock mixtures of wood, chicken manure, and food waste, and a KOH-activated biochar (40% food waste + 60% wood biochar (WFWK)) were used to remove cesium (Cs+) and strontium (Sr2+) ions from water. The physicochemical properties of the biochars before and after adsorbing Cs+ and Sr2+ were determined using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, extended X-Ray absorption fine structure (EXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX). The WFWK exhibited the highest adsorption capacity for Cs+ (62.7 mg/g) and Sr2+ (43.0 mg/g) among the biochars tested herein. The removal of radioactive 137Cs and 90Sr exceeded 80% and 47%, respectively, in the presence of competing ions like Na+ and Ca2+. The functional groups present in biochar, including -OH, -NH2, and -COOH, facilitated the adsorption of Cs+ and Sr2+. The Cs K-edge EXAFS spectra revealed that a single coordination shell was assigned to the Cs-O bonding at 3.11 Å, corresponding to an outer-sphere complex formed between Cs and the biochar. The designer biochar WFWK may be used as an effective adsorbent to treat radioactive 137Cs- and 90Sr-contaminated water generated during the operation of nuclear power plants and/or unintentional release, owing to the enrichment effect of the functional groups in biochar via alkaline activation.


Assuntos
Eliminação de Resíduos , Poluentes Químicos da Água , Adsorção , Césio/química , Carvão Vegetal , Alimentos , Humanos , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Estrôncio , Água , Poluentes Químicos da Água/análise
18.
Environ Res ; 214(Pt 4): 114085, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-35987376

RESUMO

Cesium (Cs) is a byproduct of nuclear bombs, nuclear weapons testing, and nuclear fission in nuclear reactors. Cs can enter the human body through food or air and cause lasting damage. Highly efficient and selective removal of 137Cs from low-level radioactive effluents (LLREs), which contain many radionuclides and dissolved heavy metal species, is imperative for minimizing LLRE volume, and facilitating their final disposal. Prussian blue analogs (PBAs) have received much attention as materials for the removal of radioactive Cs because of their affinity for adsorbing Cs+. In this study, an inexpensive and readily available cyanide-based functional material (PBACu) exhibiting high efficiency and excellent selectivity toward Cs capture was designed through a facile low-temperature co-precipitation process. Nano-PBACu, crystallizing in the cubic space group (Fm-3m (225)), has an average pore size of 6.53 nm; consequently, PBACu can offer abundant atomic occupation sites for capturing and incorporating Cs. Here, the pseudo-second-order kinetic model and Langmuir model fitted well with the adsorption of Cs + on PBACu, with a maximum capture capacity of 95.75 mg/g within 5 min, confirming that PBACu could rapidly capture Cs ions. PBACu strongly and selectively interacted with Cs even in a simulant containing large Na+, NH4+, Ca2+, and Mg2+ ion concentrations in an aqueous solution. The process of Cs + adsorption by cyanide-based functional crystals was confirmed to involve the entry of Cs+ into cyanide-based functional crystals to replace K+ and finally achieve the lattice incorporation of Cs. The current results broaden the lattice theory of radionuclide Cs removal and provide a promising alternative for the immobilization of Cs from radioactive wastewater.


Assuntos
Césio , Cianetos , Adsorção , Césio/química , Humanos , Concentração de Íons de Hidrogênio , Águas Residuárias/química
19.
Environ Sci Pollut Res Int ; 29(42): 64215-64224, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35882731

RESUMO

After the treatment of liquid radioactive waste, there is a certain amount of Cs in the waste resin, and these Cs-doped resins are prone to volatilize during the thermal treatment process and cause radionuclide leakage. The molten salt oxidation (MSO) can effectively prevent the volatilization of toxic metal, especially the volatilization of Cs. Under nitrogen and air conditions, it is found that the oxidation behavior between Cs-doped and clean cation exchange resins (CERs) is quite different. In the presence of oxygen and molten carbonate salt, Cs2CO3 is generated by the destruction of functional groups in Cs-doped CERs. The Cs2CO3 in Na2CO3-K2CO3-Li2CO3 reacts with oxygen to form Li2O2, which reduces the content of S in residue from 26.33 to 13.38% in air conditions at 400 °C and promotes the generation of sulfate in the molten carbonate salt. The elements Cs and S in the Cs doped CERs spontaneously form thermally stable Cs2SO4 in the molten carbonate salt.


Assuntos
Resinas de Troca de Cátion , Resíduos Radioativos , Carbonatos/química , Césio/química , Nitrogênio , Oxigênio , Cloreto de Sódio/química , Sulfatos
20.
Sci Total Environ ; 838(Pt 4): 156530, 2022 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-35679934

RESUMO

The Prussian blue (PB) blending membranes are promising candidates for the removal of trace radionuclide Cs+. Constructing a membrane with high flux and selectivity are challenging in its practical application. Here, a novel polyvinylidene fluoride (PVDF)-PB-graphene oxide (GO) modified membrane was fabricated via phase inversion for trace radionuclide cesium (137Cs) removal from water. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to analyze chemical composition and morphology of the membrane, and the properties in terms of water flux and Cs+ removal were studied under different PB dosage, pH and co-existing ions conditions. It was observed that the addition of GO improved the dispersion of PB, and the PVDF-PB-GO membrane presented the highest Cs+ removal efficiency (99.6 %) and water flux (1638.2 LMH/bar) at pH = 7 with 0.1 wt% GO and 5 wt% PB. In addition, Langmuir and pseudo-second-order kinetics models fitted well for Cs+ adsorption by the PVDF-PB-GO membrane, illustrating that the Cs+ was removed via chemical adsorption dominated by Fe(CN)64- defect sites of PB and the oxygen groups of GO. Furthermore, the membrane showed a significant selectivity and reusability towards trace radioactive cesium, even in the presence of excess co-existing ions and in real water, which strongly verified that the modified membrane had application potential.


Assuntos
Grafite , Poluentes Químicos da Água , Adsorção , Césio/química , Ferrocianetos , Polímeros de Fluorcarboneto , Grafite/química , Íons/análise , Cinética , Polivinil , Águas Residuárias/química , Água , Poluentes Químicos da Água/análise
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