A Reliable Hybrid Adsorbent for Efficient Radioactive Cesium Accumulation from Contaminated Wastewater

Potassium permanganate-modified eggshell biosorbent for the removal of diclofenac from liquid environment: adsorption performance, isotherm, kinetic, and thermodynamic analyses

This study assess how well diclofenac (DCF) can be separated from aqueous solution using potassium permanganate-modified eggshell biosorbent (MEB). The MEB produced was characterised using XRD, FTIR, and SEM. Batch experiments were conducted to examine and assess the impact of contact time, adsorbent dosage, initial concentration, and temperature on the adsorption capacity of the MEB in the DCF sequestration. The best parameters to obtained 95.64% DCF removal from liquid environment were 0.05 g MEB weight, 50 mg/L initial concentration, and 60 min contact time at room temperature. The maximum DCF sequestration capacity was found to be 159.57 mg/g with 0.05 g of MEB at 298 K. The adsorption isotherm data were more accurately predicted by the Freundlich model, indicating a process of heterogeneous multilayer adsorption. The results of the kinetic study indicated that the pseudo-second-order kinetic models best matched the experimental data. The findings revealed that the dynamic of DCF entrapment is largely chemisorption and diffusion controlled. Based on the values of thermodynamic parameters, the process is both spontaneous and endothermic. The primary processes of DCF sorption mechanism onto the MEB were chemical surface complexation, hydrogen bonding, π-π stacking, and electrostatic interactions. The produced MEB showed effective DCF separation from the aqueous solution and continued to have maximal adsorption capability even after five regeneration cycles. These findings suggest that MEB could be highly efficient adsorbent for the removal of DCF from pharmaceutical wastewater.

Limitations and Progresses in Carbon-Based Cesium Lead Halide Perovskite Solar Cells

Inorganic cesium lead halide perovskites (CsPbIxBr3-x, 0≤x≤3) are promising alternatives with great thermal stability. Additionally, the choice of moisture-resistive and dopant-free carbon as the electrode material can simultaneously solve the problems of stability and cost. Therefore, carbon electrode-based inorganic PSCs (C-IPSCs) represent a promising candidate for commercialization, yet both the efficiencies and stability of related devices demand further progress. This article reviews the recent advancement of C-IPSCs and then unravels the distinctive merits and limitations in this field. Subsequently, our perspective on various modification strategies is analyzed on a methodological level. Finally, this article outlooks the promising research contents and the remaining unresolved issues in this field. We believe that understanding and analyzing the related problems in this field are instructive to stimulate the future development of C-IPSCs.

Chitosan-minerals-based composites for adsorption of caesium, cobalt and europium

Currently, there is a growing interest in the use of natural materials in various fields of science, technology and environmental protection due to their availability, low-cost, non-toxicity and biodegradability. Chitosan, natural clay of local origin, montmorillonite, zeolite, cross-linking agents (epichlorohydrin, sodium tripolyphosphate, glutaraldehyde) and plasticisers (glycerol) were used to synthesise composites. The composites were characterised by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction analysis (XRD) and scanning electron microscope (SEM), tested for their antibacterial activity and used in batch experiments to study the adsorption of caesium, cobalt and europium ions. The maximum capacities for adsorption of caesium, cobalt and europium on the composites were 1400 mg/g, 900 mg/g and 18 mg/g, respectively. The experimental data fit better the Langmuir isotherm model and indicate favourable monolayer adsorption of Cs+, Co2+ and Eu3+ at homogeneous sites of the composites. The experimental data were in better agreement with the pseudo-second-order non-linear kinetic model for most elements and adsorbents. Adaptive neuro-fuzzy inference system proved to be a practical tool with good performance and generalisation capability for predicting the adsorption capacity of composites for caesium, cobalt, and europium ions. It was found that the predicted data were very close to the experimental data.

Cation-Intercalated Lamellar MoS2 Adsorbent Enables Highly Selective Capture of Cesium

Highly selective capture of cesium (Cs+) from complex aqueous solutions has become increasingly important owing to its (133Cs) indispensable role in some cutting-edge technologies and the environmental mobility of radioactive nuclide (137Cs) from nuclear wastewater. Herein, we report the development of cation-intercalated lamellar MoS2 as an effective Cs+ adsorbent with the advantages of facile synthesis and highly tunable layer spacing. Two types of cations, including Na+ and NH4+, were employed for the intercalations between adjacent layers of MoS2. The results demonstrated that the adsorption capacity of the NH4+-intercalated material (M-NH4+, 134 mg/g) for Cs+ clearly outperformed the others due to higher loading percentages of cations and larger layer spacing. The cesium partition coefficients for M-NH4+ in the presence of 100-fold competing ions all exceed 1 × 103 mL/g. A simulated complex aqueous solution containing 15.37 mg/L Cs+ and highly excess of competing ions Li+, Na+, K+, Mg2+, and Ca2+ (20-306 times higher) was introduced to prove the practical application potential using our best-performing M-NH4+, showing a good to excellent partition ability of Cs+ among other cations, especially for Cs/K and Cs/Na with separation factors of 58 and 212, respectively. The adsorption and selectivity mechanisms were clearly elucidated using various advanced techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. These results revealed that the good selectivity for Cs+ can be ascribed to the differences in Lewis acidities, hydration energy, cation sizes, and in particular, the divergence of coordination modes which was successfully achieved after tuning the layer distance via the cation intercalation strategy. In addition, the material has fast kinetics (<30 min), wide range of pH tolerance (4-10), and good reusability. Overall, our studies point out that the tunable lamellar MoS2-based materials are promising adsorbents for Cs+ capture and separation.

Enhanced Adsorption and Evaluation of Tetracycline Removal in an Aquatic System by Modified Silica Nanotubes

In the present study, a nanocomposite adsorbent based on mesoporous silica nanotubes (MSNTs) loaded with 3-aminopropyltriethoxysilane (3-APTES@MSNTs) was synthesized. The nanocomposite was employed as an effective adsorbent for the adsorption of tetracycline (TC) antibiotics from aqueous media. It has an 848.80 mg/g maximal TC adsorption capability. The structure and properties of 3-APTES@MSNT nanoadsorbent were detected by TEM, XRD, SEM, FTIR, and N₂ adsorption-desorption isotherms. The later analysis suggested that the 3-APTES@MSNT nanoadsorbent has abundant surface functional groups, effective pore size distribution, a larger pore volume, and a relatively higher surface area. Furthermore, the influence of key adsorption parameters, including ambient temperature, ionic strength, initial TC concentration, contact time, initial pH, coexisting ions, and adsorbent dosage, had also been investigated. The 3-APTES@MSNT nanoadsorbent's ability to adsorb the TC molecules was found to be more compatible with Langmuir isothermal and pseudo-second-order kinetic models. Moreover, research on temperature profiles pointed to the process' endothermic character. In combination with the characterization findings, it was logically concluded that the 3-APTES@MSNT nanoadsorbent's primary adsorption processes involved interaction, electrostatic interaction, hydrogen bonding interaction, and the pore-fling effect. The synthesized 3-APTES@MSNT nanoadsorbent has an interestingly high recyclability of >84.6 percent up to the fifth cycle. The 3-APTES@MSNT nanoadsorbent, therefore, showed promise for TC removal and environmental cleanup.

Three-dimension titanium phosphate aerogel for selective removal of radioactive strontium(II) from contaminated waters

The effective removal of radioactive strontium (especially ⁹⁰Sr) from nuclear wastewater is crucial to environmental safety. Nevertheless, materials with excellent selectivity in Sr removal remain a challenge since the similarity with alkaline earth metal ions in the liquid phase. In this work, a novel titanium phosphate (TiP) aerogel was investigated for Sr(II) removal from the radioactive wastewater based on the sol-gel method and supercritical drying technique. The TiP aerogel has amorphous, three-dimensional and mesoporous structures with abundant phosphate groups, which was confirmed by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), atomic force microscope (AFM) and Fourier transform infrared spectroscopy (FT-IR). The adsorbent exhibited high efficiency and selectivity for the removal of Sr(II) with an extensive distribution coefficient up to 4740.03 mL/g. The adsorption equilibrium reached within 10 min and the maximum adsorption capacity was 373.6 mg/g at pH 5. And the kinetics and thermodynamics data fitted well with the pseudo-second-order model and Langmuir model respectively. It can be attributed to the rapid trapping and slow intraparticle diffusion of Sr(II) inside the mesoporous channels of the TiP aerogel. Furthermore, TiP aerogel exhibited over 80% removal for 50 mg/L Sr²⁺ in real water systems (seawater, lake water and tap water). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy revealed that strong ionic bonding formed during Sr(II) adsorption with the phosphate group on TiP aerogel. These results indicated that TiP aerogel is a promising high-capacity adsorbent for the effective and selective capture of Sr(II) from radioactive wastewater.

Scintillation Response of Nd-Doped LaMgAl11O19 Single Crystals Emitting NIR Photons for High-Dose Monitoring

The Nd-doped LaMgAl₁₁O₁₉ single crystals were synthesized by the floating zone method, and the photoluminescence and scintillation properties were evaluated. Under X-ray irradiation, several sharp emission peaks due to the 4f-4f transitions of Nd³⁺ were observed at 900, 1060, and 1340 nm in the near-infrared range, and the decay curves show the typical decay time for Nd³⁺. The samples show good afterglow properties comparable with practical X-ray scintillators. The 1% and 3% Nd-doped LaMgAl₁₁O₁₉ samples show a good linearity in the dynamic range from 6-60,000 mGy/h.

Microwave-assisted synthesis of MnO2 nanosorbent for adsorptive removal of Cs(I) and Sr(II) from water solutions

In this study, a flower-like porous δ-MnO₂ nanostructure was synthesized by a microwave-assisted hydrothermal process for adsorptive removal of strontium (Sr(II)) and cesium (Cs(I)) from wastewater. The prepared δ-MnO₂ nanosorbent exhibited superior affinity for Sr(II) over Cs(I) in the single-solute system, with partition coefficient (PC) values of 10.2 and 2.3 L/g, respectively, at pH 6.0. In the two-solute system, the flower-like δ-MnO₂ also adsorbed Sr(II) (PC = 3.81 L/g) more selectively than Cs(I) (PC 1.15 L/g). Further, their adsorption capacities decreased by 12 and 16%, respectively, relative to the single-solute system. In contrast, adsorption of the ions onto δ-MnO₂ was affected less sensitively in dual than in single system when changes occurred in environmental variables such as pH (2-8) and ionic strength (1-100 mM). Adsorption kinetics, thermodynamics, and isotherm studies demonstrated the pivotal role of the monolayer surface active sites of endothermic δ-MnO₂ (e.g., a complexation interaction with Mn-OH). Furthermore, the δ-MnO₂ nanosorbent exhibited good regenerability, retaining more than 80% of its adsorption capacity when tested over four reuse cycles. The overall results of this study are expected to help establish strategies to effectively remove metal contaminants from wastewater using a green and low-cost hierarchical nanosorbent.

Highly selective and easily regenerated porous fibrous composite of PSF-Na2.1Ni0.05Sn2.95S7 for the sustainable removal of cesium from wastewater

The removal of ¹³⁷Cs from radioactive wastewater remains a huge challenge due to the interference of many coexisting ions. Several tin chalcogenides (X₂Sn₃Y₇, XNa, K; YTe, Se, S) were synthesized and screened for highly selective cesium removal from radioactive wastewater. It was found that Na₂Sn₃S₇ showed the best adsorption performance for low cesium concentrations. Especially after nickel doping, the adsorption capacity and thermal stability of the adsorbent were significantly enhanced. Its maximum adsorption capacity reached 436.72 mg·g^-1 within only 5 min and adsorption performance kept active in the pH range of 2-12. After being coated with a porous polysulfone (PSF) fiber, the developed PSF-Na_2.1Ni_0.05Sn_2.95S₇ was applied to natural complex water with cesium concentration of 17.58 mg·L^-1. The separation factors between Cs⁺ and competitive ions ranged from 625.21 to 13123.21. It is noteworthy that NaNO₃ was an efficient regenerating agent and can be easily separated from the CsNO₃ mixture for cyclic utilization. Remarkably, only 45 min in each cycle of adsorption and desorption toward cesium was realized, and the adsorption properties hardly decreased even after 50 consecutive cycles. The above advantages make the proposed material an excellent candidate for efficient Cs⁺ removal and enrichment from wastewater.

Hyper-crosslinked tetraphenylborate as a regenerable sorbent for Cs+ sequestration in aqueous media through cation-π interactions

Practical adsorbents that could efficiently collect radioactive Cesium (Cs⁺) are critically important in achieving proper management and treatment measures for nuclear wastes. Herein, a hyper-crosslinked tetraphenylborate-based adsorbent (TPB-X) was prepared by reacting TPB anions as Cs⁺ binding sites with dimethoxymethane (DMM) as crosslinker. The most efficient TPB-X synthesis was attained at 1:4 TPB/DMM mole ratio with sorbent yield of 81.75%. Various techniques such as FTIR, TGA-DTG, N₂ adsorption/desorption and SEM-EDS reveal that TPB-X is a water-insoluble, thermally stable and highly porous granular sorbent. Its hierarchical pore structure explains its very high BET surface area (1030 m² g^-1). Sequestration of Cs⁺ by TPB-X involves its exchange with H⁺ followed by its binding with the phenyl rings of TPB through cation-π interactions. The Cs⁺ adsorption in TPB-X is endothermic and spontaneous, which adheres to the Hill isotherm model (q_m = 140.58 mg g^-1) and follows pseudo-second order kinetics (k₂ = 0.063 g mg^-1 h^-1). Calculations from the density functional theory reveal that the binding of TPB anion is strongest for Cs⁺. Thus, TPB-X was able to selectively capture Cs⁺ in simulated surface water containing Na⁺, K⁺, Mg²⁺, and Ca²⁺ and in HLLW containing Na⁺, Rb⁺, Sr²⁺, and Ba²⁺. Hyper-crosslinking was found beneficial in rendering TPB-X reusable as the sorbent was easily retrieved from the feed after Cs⁺ capture and was able to withstand the acid treatment for its regeneration. TPB-X exhibited consistent performance with no sign of chemical or physical deterioration. TPB-X offers a practical approach in handling Cs⁺ contaminated streams as it can be repeatedly used to enrich Cs⁺ in smaller volume of media, which can then be purified for Cs⁺ reuse or stored for long-term natural Cs⁺ decay process.

Selective Separation of Radiocesium from Complex Aqueous Matrices Using Dual Solid-Phase Extraction Systems

The release of radiocesium (r-Cs) into natural aqueous systems is of concern because of its extended solubility as an alkaline metal ion and its facile incorporation into living beings. A technique for the selective separation of Cs from an aqueous matrix using dual solid-phase extraction (SPE) systems in a series is proposed in this paper. The SPEs equipped with chelates (Nobias Chelate-PA1 and Nobias Chelate-PB1), an ion-exchange resin (Nobias Ion SC-1), or macrocycles (MetaSEP AnaLig Cs-01 and MetaSEP AnaLig Cs-02) were evaluated in terms of selectivity and retention/recovery behavior toward Cs and other potentially competing ions (Li, Na, K, Rb, Ba, Ca, Mg, and Sr). The simulated solution of ¹³³Cs, a chemical analog of r-Cs, was used to optimize the separation process. Operating parameters such as pH (3-13), flow rate (0.2-5.0 mL min^-1), and elution behavior (HCl, 0.1-5.0 mol L^-1) were optimized to ensure maximum removal of Cs from the aqueous matrices. The dual SPE system comprised Nobias Chelate-PB1 that minimized the competing impact of ions, while selective Cs retention was attained with MetaSEP AnaLig Cs-02. The proposed process was verified using real r-Cs-contaminated water from Fukushima, Japan, to observe the quantitative separation and preconcentration of r-Cs from the complex matrices.

Effective removal of 137Cs ions from radioactive wastewater by Melamine-Styrene based Polymer (MSP)

Cesium (Cs) is a major product of uranium fission, which is one of the most existed radionuclides in radioactive wastes. Removal of Cs-137 has a critical role in the decontamination of liquid radioactive waste due to its half-life of 30.17 years. Concordantly, melamine styrene based conjugated polymer (MSP) was designed, synthesized, and characterized with FTIR, TGA, SEM and BET measurements. The novelty of the study is that the MSP adsorbent is designed as a highly conjugated structure to have better interaction with Cs over the Cs-π bond of the benzene groups of the adsorbent. In this work, the adsorption behavior and rate of MSP were investigated as parameters of adsorbent amount, pH, contact time, particle size, initial Cs⁺ concentration, and temperature. Besides, the adsorption efficiency of Cs-137 was examined by Gamma Spectroscopy. Adsorption results were fitted to three different isotherms which were Freundlich, Langmuir and Dubinin-Radushkevich (D-R). The maximum adsorption capacity of polymer for Cs⁺ ion was found from Langmuir isotherm as 78 mg g^-1. As a part of kinetic parameters, pseudo first and second orders were investigated and in terms of the correlation coefficient pseudo second order was much more appropriate for adsorption of Cs-137 onto MSP.

Sequestration of p-nitrophenol from liquid phase by poly(acrylonitrile-co-acrylic acid) containing thioamide group

In this paper, the adsorptive performance of synthesized thiourea (TU) modified poly(acrylonitrile-co-acrylic acid) (TU-P(AN-co-AA)) polymeric adsorbent for capturing p-nitrophenol (PNP) from aqueous solution was investigated. TU-P(AN-co-AA) was synthesized via the redox polymerization method with acrylonitrile (AN) and acrylic acid (AA) as the monomers, then modified chemically with thiourea (TU). Characterization analysis with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), elemental microanalysis for CHNS, zeta potential measurement, Brunauer-Emmett-Teller (BET) surface analysis and thermal analyses were carried out to determine the morphology and physico-chemical properties of the synthesized polymer. The characterization results indicated successful surface modification of polymer with TU. The performance of TU-P(AN-co-AA) for the removal of PNP was investigated under various experimental parameters (adsorbent dosage, initial adsorbate concentration, contact time and temperature). The results demonstrated that the Freundlich isotherm model and pseudo-second-order kinetic model best described the equilibrium and kinetic data, respectively. Thermodynamic studies showed that the uptake of PNP by TU-P(AN-co-AA) was spontaneous and exothermic in nature. The results of the regeneration studies suggested that the TU-P(AN-co-AA) polymer is a reusable adsorbent with great potential for removing PNP from wastewater.

Novel micro-structured carbon-based adsorbents for notorious arsenic removal from wastewater

The contamination of groundwater by arsenic (As) in Bangladesh is the biggest impairing of a population, with a large number of peoples affected. Specifically, groundwater of Gangetic Delta is alarmingly contaminated with arsenic. Similar, perilous circumstances exist in many other countries and consequently, there is a dire need to develop cost-effective decentralized filtration unit utilizing low-cost adsorbents for eliminating arsenic from water. Morphological synthesis of carbon with unique spherical, nanorod, and massive nanostructures were achieved by solvothermal method. Owing to their intrinsic adsorption properties and different nanostructures, these nanostructures were employed as adsorption of arsenic in aqueous solution, with the purpose to better understanding the morphological effect in adsorption. It clearly demonstrated that carbon with nanorods morphology exhibited an excellent adsorption activity of arsenite (about 82%) at pH 3, remarkably superior to the two with solid sphere and massive microstructures, because of its larger specific surface area, enhanced acid strength and improved adsorption capacity. Furthermore, we discovered that iron hydroxide radicals and energy-induced contact point formation in nanorods are the responsible for the high adsorption of As in aqueous solution. Thus, our work provides insides into the microstructure-dependent capability of different carbon for As adsorption applications.

Assessing of cesium removal from wastewater using functionalized wood cellulosic adsorbent

Sustainable materials are urgently desired for treatment of radioactive cesium (Cs) contaminated water to safe-guard the public health. Apart from the synthetic ligand-based materials, the Mangrove charcoal modified adsorbent was fabricated for assessing of Cs removal from waste sample. The raw charcoal was oxidized using nitrification approach and diverse oxygen containing carboxyl, carbonyl and hydroxyl functional groups were introduced. After modification, the adsorbent characteristics were drastically changed as compared to the charcoal during the measurement of FTIR, N₂ adsorption-desorption isotherms and SEM micrographs. The data clarified that charcoal modified adsorbent was exhibited high Cs transport through the inner surface of the adsorbent based on bonding ability. The adsorbent was shown comparatively slow kinetics to Cs ion; however, the adsorption capacity was high as 133.54 mg/g, which was higher than the crown ether based conjugate materials. The adsorption data were followed to the Langmuir adsorption isotherms and the monolayer coverage was possible due to the data presentation. The presence of high amount of Na and K were slightly interfered to the Cs adsorption by the charcoal modified adsorbent, however; the Na and K concentration was 350-600 folds higher than the Cs concentration. Then the proposed adsorbent was selective to Cs for the potential real radioactive Cs contaminated water. The volume reduction was established rather than desorption and reuses advantages. More than 99% volume reduction was measured by burning of Cs adsorbed adsorbent at 500 °C for ensuring the safe storage and disposal of used adsorbent. Therefore, the charcoal modified adsorbent may open the new door to treat the Cs containing wastewater.

Statistical techniques for the optimization of cesium removal from aqueous solutions onto iron-based nanoparticle-zeolite composites

Statistical optimization of performance determining factors is essential for the development of a cesium removal system from aqueous solutions. Therefore, factorial experimental design and multiple regression techniques were employed to assess the primary and interaction effects of the pH, initial concentration, and contact time in the cesium removal process using nanoscale zero-valent iron-zeolite (nZVI-Z) and nano-Fe/Cu-zeolite (nFe/Cu-Z) as an adsorbent. The optimum region of cesium removal was identified by constructing a contour plot. The study revealed that initial concentration was the most significant factor followed by contact time. The study also suggested that maximum cesium removal occurred at pH, initial concentration, and contact time of 6, 200 mg/L, and 30 min, respectively. Moreover, the statistically significant interaction effect was observed between contact time and initial concentration. The experimental data were also fitted with Tόth, Langmuir, Dubinin-Astakhov (D-A), Freundlich, and Hill models and found that the Tόth model fitted better compared with the other four models based on Akaike information criterion (AIC) and root-mean-square deviation (RMSD). The findings of this paper can undoubtedly contribute to constructing the optimum statistical process of removing hazardous pollutants from the water, which significantly impacts on human health and the environment. Graphical abstract.

Dual Ion-Imprinted Mesoporous Silica for Selective Adsorption of U(VI) and Cs(I) through Multiple Interactions

Separation of uranium and cesium from low-level radioactive effluents (LLRE) is of great significance for sustainable development of the nuclear industry and for the environment. However, high salinity and massive coexisting ions of LLRE are giant challenges for the separation. To address the challenges, we report a strategy for efficient and simultaneous separation of uranium and cesium from a high-salt environment by dual ion-imprinted mesoporous silica based on multiple interactions. The as-prepared adsorbents can reach equilibrium for uranium and cesium within 1 h with a maximum capacity of 221.7 mg U g^-1 and 34.5 mg Cs g^-1. The sorption mechanism demonstrates that the highly active phenolic hydroxyl groups of imprinted cavities can extract uranium and cesium effectively through multiple interactions, including coulomb attraction, redox, ion exchange, and complexation. The synergism of multiple interactions and imprinted cavity endows the sorbent with good selectivity for uranium and cesium over other cations and with excellent salt tolerance. This work demonstrates a new strategy of selective extraction of nuclides by multifunction adsorbent through multiple interactions.

Synthesis and Adsorption Behavior of Microporous Iron-Doped Sodium Zirconosilicate with the Structure of Elpidite

Decontamination of water from radionuclides contaminants is a key priority in environmental cleanup and requires intensive effort to be cleared. In this paper, a microporous iron-doped zeolite-like sodium zirconosilicate (F@SZS) was designed through hydrothermal synthesis with various Si/Zr ratios of 5, 10, and 20, respectively. The synthesized materials of F@SZS materials were well characterized by various techniques such as XRD, SEM, TEM, and N2 adsorption–desorption measurements. Furthermore, the F@SZS-5 and F@SZS-10 samples had a crystalline structure related to the Zr–O–Si bond, unlike the F@SZS-20 which had an overall amorphous structure. The fabricated F@SZS-5 nanocomposite showed a superb capability to remove cesium ions from ultra-dilute concentrations, and the maximum adsorption capacity was 21.5 mg g–1 at natural pH values through an ion exchange mechanism. The results of cesium ions adsorption were found to follow the pseudo-first-order kinetics and the Langmuir isotherm model. The microporous iron-doped sodium zirconosilicate is described as an adsorbent candidate for the removal of ultra-traces concentrations of Cs(I) ions.

Efficient cesium encapsulation from contaminated water by cellulosic biomass based activated wood charcoal

In this study, cost-effective cellulosic biomass based activated wood charcoal was developed from Japanese Sugi tree (Cryptomeria japonica) by concentrated nitric acid modification for adsorption of Cs from contaminated water. The physicochemical properties of specimens were investigated using N₂ adsorption-desorption isotherms (BET method), FESEM, FTIR, and XPS spectra analysis. The experimental results revealed that the surface area of the raw wood charcoal was significantly decreased after boiling nitric acid modification. However, several oxygen-containing acidic function groups (-COOH, -CO) were introduced on the surface. The adsorption study confirmed that the equilibrium contact time was 1 h, the optimum adsorption pH was neutral to alkaline and the suitable adsorbent dose was 1:100 (solid: liquid). The maximum Cs was removed when the concentration of Na and K were lower (5.0 mM) with Cs in solution. The Cs adsorption processes well approved by the Langmuir isotherm and pseudo-second-order kinetic models and the maximum adsorption capacity was 35.46 mgg^-1. The Cs adsorption mechanism was clearly described and it was assumed that the adsorption was strongly followed by chemisorptions mechanism based on the adsorbent surface properties, kinetic model and Langmuir isotherm model. Most importantly, about 98% of volume reduction was obtained by burning (500 °C) the Cs adsorbed charcoal, which ensured safe storage and disposal of radioactive waste. Therefore, this study can offer a guideline to produce a functional adsorbent for effective Cs removal and safe radioactive waste disposal.

Effective removal of radioactive cesium from contaminated water by synthesized composite adsorbent and its thermal treatment for enhanced storage stability

A composite adsorbent for the removal of radioactive cesium (¹³⁷Cs) was synthesized by immobilizing potassium cobalt ferrocyanide in the micro pores of the zeolite chabazite. The synthetically optimized composite adsorbent demonstrates a rapid cesium adsorption rate under both salt-free and high-salt conditions with a high distribution coefficient of cesium (≥10⁵ mL/g). Although both components have the same ion-exchange reaction between potassium and cesium, the reaction by ferrocyanide component was predominant, which derived hundred times higher distribution coefficient of the composite adsorbent than that of pure chabazite. A thermal stabilization process was studied for improving the storage and/or disposal stability of the spent adsorbent. The formation of a eutectic system within the spent adsorbent reduced the stabilization temperature to 1000 °C from 1200 °C. Accordingly, the leaching of cesium was remarkably reduced by the remineralization to the stable pollucite. The stable impregnation of ferrocyanide component in the chabazite pores derived the reduction of cesium volatility enabling the high temperature stabilization method. Our experimental results provide evidence that the composite adsorbent has clear advantages on the cesium removal from contaminated water and its stabilization via thermal-treatment.

Fluorescent and colorimetric dual-response sensor based on copper (II)-decorated graphitic carbon nitride nanosheets for detection of toxic organophosphorus

An efficient and convenient detection method for organophosphorus pesticide (OP) residues is needed because of their high neurotoxicity and severe threat to food safety. OPs effectively reduce the production of thiocholine in the acetylcholinesterase/acetylthiocholine reaction by inhibiting the activity of acetylcholinesterase. Therefore, we developed a feasible and convenient fluorescent and colorimetric dual-response sensor based on the competitive complexation of Cu²⁺ between graphitic carbon nitride nanosheets and thiocholine for the rapid detection of OPs with high sensitivity. Malathion was used as a model OP, and a linear range of 70-800 nM with a detection limit of 6.798 nM for a fluorescent signaling platform and 2.5-25 nM with a detection limit of 1.204 nM for a colorimetric probe were attained. The constructed probe was successfully applied to determine OP in actual samples of cabbages leaves and tap water. The results indicated that the dual-response probe was reliable and sensitive to actual samples.

Selective adsorption of sodium dodecylbenzenesulfonate from a Cs ion mixture by electrospun mesoporous silica nanofibers

Sodium dodecylbenzenesulfonate (SDBS) is commonly used to remove radioactive nuclides such as Cs ions during decontamination of shut-down nuclear power plants. Potential environmental problems still remain because of the incomplete removal of large amounts of SDBS from radioactive liquid waste. For the first time, mesoporous silica nanofibers (MSFs) were fabricated for an efficient SDBS separation. MSFs were prepared by electrospinning using tetraethyl orthosilicate, a surfactant, and a template polymer; the product had a large surface area, a high pore volume, and a uniform pore size distribution. The internal pores or external surface were modified with quaternary ammonium salt, providing affinity to water and an electrostatic interaction with SDBS. The MSF-based adsorbent had excellent adsorption ability for SDBS (158.98 mg/g) over conventional adsorbents. In addition, the MSF-based adsorbent could selectively adsorb SDBS from a mixed solution of SDBS and Cs ions. Judging from the Freundlich pseuso second-order kinetic adsorption, the adsorption isotherm indicated that the SDBS adsorption was a kind of multilayer physisorption.