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Extraction of rubidium and cesium from a leach solution of lepidolite with biomass carbon adsorbents
Abstract
Two biomass carbon adsorbents ([email protected] and [email protected]) modified with potassium titanosilicate (PTS) were prepared by a hydrothermal deposition method and characterized by means of SEM-EDS, BET, FTIR, XRD, and XPS. The results show that the adsorbents have mesoporous structures, and potassium titanosilicate ((HK3)O2∙3SiO2∙4TiO2∙4H2O) was immobilized in the biomass carbon structure. The adsorption properties of these two adsorbents for rubidium (Rb⁺) and cesium (Cs⁺) from an aqueous solution and the tail liquor after extracting lithium from lepidolite were systematically studied. The adsorption amounts increased with increasing pH and decreased with increasing KCl concentration, which were mainly due to the competitive adsorption between H⁺ or K⁺ and Rb⁺ or Cs⁺ in solution. The adsorption kinetics of the adsorbents were consistent with the pseudosecondary kinetic model, which indicated that chemical adsorption played a leading role in the adsorption process. The adsorption capacities of Rb⁺ and Cs⁺ reached 2.57 mmol g⁻¹ and 2.12 mmol g⁻¹, respectively. The adsorption mechanism of Rb⁺ and Cs⁺ on the adsorbents was proposed as the ion-exchange between K⁺ in the adsorbents and Rb⁺/Cs⁺ in the solution. In addition, the adsorbents showed high extraction efficiency for Rb⁺ and Cs⁺ from two different lithium extraction tail liquors of lepidolite. Therefore, the obtained adsorbents in this work have excellent adsorption performance and show great potential as adsorption materials for Rb⁺ and Cs⁺.
... The first approach involves the extraction of valuable minerals from solid waste by employing various physical or chemical techniques. For instance, in the domain of recycling and utilization of lepidolite tailings and other lepidolite solid wastes, Siame E et al. [14] extracted lithium from the waste materials stored in lepidolite tailings.Qian Y et al. [15]employed a hydrothermal deposition method to synthesize two types of biomass-based carbon adsorbents modified with potassium titanate silicate, thereby facilitating the extraction of rubidium and cesium from two distinct lithium mica tailings solutions. Phan T T et al. [16] employed a modified Synthetic Precipitation Leaching Procedure (SPLP) to evaluate the efficacy of four readily accessible amendments (peat, clay, biochar, and topsoil) in mitigating the release of thallium (Tl) from the solid by-products of lithium mica extraction. ...
... Some researchers Abhishek et al., 2022;Creamer and Gao, 2016;Kim et al., 2022;Shewchuk et al., 2021) suggested that carbon-adsorbing materials like zeolites or activated carbon could be utilised in cementitious composites to sequestrate CO 2 and satisfy the requirement of low-carbon concrete. However, the cost of these carbon adsorbents is relatively high, thus limiting their use by the concrete industry (Creamer and Gao, 2016;Huang et al., 2022;Zhao et al., 2022;Qian et al., 2022;Park et al., 2022). Hence, the need of more suitable CO 2 -adsorbing materials in sequestering greenhouse gas is identified. ...
Biochar has been increasingly used in the production of cementitious materials due to its low cost, low-carbon emission, and environmental benefits. This study provides a comprehensive review on the effect of biochar on the performance of cementitious composites, focusing on mechanical properties, durability properties, and carbon-sequestration capacity. It has been observed that the use of biochar can improve the mechanical strength, thermal and electromagnetic performance of hardened biochar-cement composites. The optimum cement replacement with biochar is 1–2 wt% for enhancing the compressive and the flexural strength. Additionally, the addition of biochar can improve the resistance to sulphate attacks, chloride-induced corrosion, shrinkage, and permeability of biochar-cement composites. Biochar also has the potential to reduce the permeability of concrete, with no significant differences observed in permeability reduction for biochar processed at different pyrolysis temperatures. The positive effect of biochar (up to 5 wt%) on durability improvement is attributed to better hydration and physical filling, resulting in a denser microstructure that prevents ions and water penetrations. This study also discusses the impact of biochar on carbon sequestration capacity, demonstrating its ability to enhance the carbon-sequestration capacity of biochar-based concrete. In conclusion, while the mechanical properties of concrete with biochar have been extensively investigated, future research is needed to explore the long-term durability properties under different environmental conditions. Moreover, there is a growing demand for low-carbon concrete that utilizes carbon-negative materials to enhance performance and resilience.
... The available literature includes many publications describing the adsorption of Cu(II) and Zn(II) ions from aqueous solutions on various types of adsorbents. Oxide, clay, polymer, hybrid and activated carbon sorbents have been tested or used (Rivera-Utrilla et al., 2011;Tauetsile et al., 2018;Chen et al., 2019;Souza et al., 2018;Qian et al., 2022;Awual, 2019;Kubra et al., 2021;Shahat et al., 2018;Mazurek et al., 2020). However, a large number of these materials are characterised by low efficiency, poor selectivity and, above all, high cost of synthesis, which limit their use on an industrial scale. ...
The development of an efficient and green adsorbent is of great significance for copper(II) and zinc(II) removal and recovery from industrial wastewater. In this study, for the first time, waste rapeseed cake is used as a biosource to synthesize MgO-SO3 enriched biochar. The newly developed adsorbent was produced in a one-step process by pyrolysis at 973.15 K for 2 h, under anoxic conditions. Porous structure, specific surface area, and composition of biochar were studied. Furthermore, sorption properties of the obtained biochar in relation to copper(II), zinc(II), and arsenic(III) ions were also studied. The impact of parameters such as: sorption time, temperature, adsorbate concentration, sorbent mass, and solution pH on the efficiency of the adsorption process of the studied cations was examined. Rapeseed cake biochar exhibits good Cu(II) adsorption capacity (90.4 mg
g-1) with a short equilibrium time (4 h), which indicates the competitiveness to similar adsorbents. The adsorption of Cu(II) on the biochar was more consistent with the pseudo-second-order kinetic models and Langmuir model. The Freundlich and pseudo-second-order kinetic models best fitted the removal of Zn(II) by
modified biochar. The mechanism of Cu(II) and Zn(II) adsorption was also postulated. Experimental data collected have shown that the presence of arsenic(III) at higher concentrations adversely affects the sorption efficiency of Cu(II) and Zn(II) ions. Thus, this study shows that the sorbent can be successfully used for the
separation of Cu(II) and Zn(II) from technological wastewaters. A flowsheet for the proposed process is presented.
Rubidium (Rb), a rare and precious metal, is widely used in high‐tech fields. In this work the structural advantages of mordenite (MOR) and group affinity of phenolic hydroxyl polymers (poly (styrene‐4‐hydroxystyrene) (P(S‐co‐VPh)) are combined to prepare MOR/P(S‐co‐VPh) nanofiber composite membranes with high selectivity and adsorption specificity for Rb ⁺ by electrospinning. The test results show that MOR is successfully anchored on the nanofiber substrate and maintained its complete crystal structure. Adsorption experiments show that the adsorption capacity of Rb ⁺ increases with the increase of MOR content, and pH = 9.0, T = 25°C are the best adsorption conditions. K ⁺ shows the most obvious interference with the adsorption capacity decreased from 60.03 to 39.33 mg/g. The adsorption process follows with the Langmuir isothermal model and pseudo‐second‐order kinetic equation. The chemical adsorption based on the coordination reaction is the control step, and the intraparticle diffusion also has an important effect on the adsorption rate. The recycling test indicates that the prepared nanofiber composite membrane not only has efficient adsorption of Rb ⁺ , but also exhibits excellent regeneration and stability, which helps to achieve its widespread application and long‐term operation in harsh environments.
Based on a translated Japanese title published in 2012, this book provides fundamental aspects of experimental and computational methods, the properties and structure of solvents, ion solvation and equilibria and reactions of metal complexes in solution. It includes state-of-the-art details on metal complexes in newly developing sustainable liquids and applications in real life.
Appealing to researchers working in coordination chemistry, including students and industrialists, the text uses exercises, tables and figures to help the reader with their understanding of the topic.
Highly selective and efficient rubidium ion (Rb⁺) capture from high salinity aqueous solutions has always been an extremely challenging task. Herein, a novel Rb⁺ selective adsorption nanofiber membranes are fabricated via electrospun by using a linear polymer poly(styrene-co-4-hydroxylstyrene) (P(S-co-VPh)) containing phenolic hydroxyl groups, which hydrolyzed from the copolymer of styrene (St) and 4-acetoxystyrene (AS). GPC, ¹H NMR and FTIR, results showing that the polymer chain structures can be effectively regulated via changing the monomers ratio. After electrospinning, the morphologies and specific surface areas of as-prepared membranes are evaluated by FESEM and BET. The adsorption experiment results show that Rb⁺ adsorption capacity gradually increase with phenolic hydroxyl group density of the membrane surfaces. The adsorption process agrees with the Langmuir model, and the maximum adsorption capacity (qm) is up to 53.15 mg/g, and the adsorption kinetics obeys preferentially the pseudo-second-order kinetics. Intraparticle diffusion model shows that the adsorption is a multi-step limiting process and breakthrough curve is best fitted by the Yan model. Surprising, over 80% of the maximum adsorption capacity can be achieved within 15 min, and adsorption equilibrium is reached within 1.0 h. Furthermore, the excellent selectivity coefficient K of Rb⁺/Mⁿ⁺ in high salinity binary mixtures are 580.2, 426.4, 258.1 and 128.3 for Na⁺ (9.6 g/L), Mg²⁺ (1.28 g/L), Ca²⁺ (0.4 g/L), K⁺ (0.5 g/L) used as the interfering ions, respectively. Moreover, the recovery rate remains exceeding 85% after five adsorption–desorption cycles, indicating that nanofiber membranes prepared by P(S-co-VPh) have significant application potential for rubidium separation and purification in the future.
Developing a stable and efficient adsorbent to recover Cs⁺ from liquid resources or to remove radioactive Cs⁺ from wastewater is challenging. In this study, the precursor Cs2Ti6O13 (CTO) was synthesized by the solvothermal and solid-phase sintering methods for the first time, then it was acid-modified to synthesize a novel H-type titanium-based material (H-CTO nanosheets). A series of batch adsorption experiments was carried out. The adsorption of Cs⁺ on H-CTO was evaluated under different experimental conditions, including contact time, temperature, initial Cs⁺ concentration, pH, and interfering ions. Experiments show that H-CTO exhibits a larger adsorption capacity (329 mg/g) and better cycle performance than the currently reported titanium-based adsorbents. The cesium ions were easily eluted by the 0.2 M HCl solution; the adsorption capacity did not decrease significantly after five cycles. Furthermore, the adsorption behavior of Cs⁺ on H-CTO can be described by the Langmuir isotherm and pseudo-second-order kinetic models. Characterization using IR and Raman spectroscopic analyses indicates that the adsorption mechanism of Cs⁺ on H-CTO involves OH bond cleavage and OCs bond formation. Thermodynamic studies showed that low temperatures are favorable for Cs⁺ adsorption and are spontaneous. Overall, the results suggest that H-CTO nanosheets are promising for the recovery or removal of Cs⁺ ions from Cs-containing liquid ores or radioactive wastewater.
Spinel‐structured Li1.6Mn1.6O4 (LMO) has received wide attention as ion sieve for the recovery of lithium from aqueous lithium resources. In this work, the branched‐like LMO particles were prepared via calcinating orthorhombic LiMnO2. After extracting of Li⁺ in hydrochloric acid, the branched‐like H1.6Mn1.6O4 (HMO) was obtained. During the preparing process, the structure, morphologies of LMO and HMO were characterized by XRD and SEM. The results indicated that HMO maintained the spinel and ordered array structure, which was beneficial to the lithium uptake behavior. Compared to normal HMO nanoparticles, the Li⁺ adsorption capacity of HMO by order array branched‐like structure can reach to 43.8 mg/g while rod‐like was 35 mg/g (CLi: 150 mg/L, pH 11, T: 25°C). The adsorption behaviors were well simulated by the pseudo‐second‐order and the Langmuir models. The reusability of the HMO implies that the branched‐like HMO is a potential adsorbent for Li⁺ recovery from aqueous lithium resources.
Gas adsorption is an important tool for the characterisation of porous solids and fine powders. Major advances in recent years have made it necessary to update the 1985 IUPAC manual on Reporting Physisorption Data for Gas/Solid Systems. The aims of the present document are to clarify and standardise the presentation, nomenclature and methodology associated with the application of physisorption for surface area assessment and pore size analysis and to draw attention to remaining problems in the interpretation of physisorption data.
Renewable, cost-effective and eco-friendly electrode materials have drawn much attention in energy conversion and storage fields. Bagasse, the waste product from sugarcane, mainly contains cellulose derivatives, can be a promising candidate to manufacture supercapacitor electrode materials. This study demonstrates the fabrication and characterizations of highly porous carbon aerogels by using bagasse as raw material. Macro and mesoporous carbon was firstly prepared by carbonizing the freeze drying bagasse aerogel and consequently microporous structure was created on the walls of mesoporous carbon by chemical activation. Interestingly, it was observed that the specific surface area, the pore size and distribution of the hierarchical porous carbon were affected by the activation temperature. In order to evaluate the ability of the hierarchical porous carbon towards supercapacitor electrode performance, solid state symmetric supercapacitors were assembled which demonstrated a comparable high specific capacitance of 142.1 F g-1 at discharge current of 0.5 A g-1. The fabricated solid state supercapacitor displayed excellent capacitance retention of 93.86% over 5000 cycles. The high energy storage ability of the hierarchical porous carbon was attributed to the specially designed pore structures, i.e., co-existence of the micropores and mesopores. This research has demonstrated that utilization of sustainable biopolymers as the raw materials for high performance supercapacitor electrode materials are the effective way to fabricate low-cost energy storage devices.
Carbon aerogels with large open pores and high surface area are fabricated via pyrolysis of a readily available natural resource, e.g., bacterial nanocellulose (BNC) aerogels. Freeze-drying of the BNC hydrogels is used to preserve the 3D open network structure upon calcination whereas using Fe(III) improves the yield and H/C ratio. These carbon aerogels are explored as anodes in lithium ion batteries where it is shown that they deliver superior capacity retention and rate performance compared to other carbon-based materials.
The use of in-situ X-ray and neutron diffraction has elucidated the differences in the mechanism of ion exchange between a titanium silicate and a phase in which Nb is substituted for Ti at the 25% level both with the sitinakite structure. The area of interest is the very high level of selectivity required of the exchangers for use in nuclear waste systems.
This study investigated the pressure leaching of lithium and other valuable metals from lepidolite using NaOH and Ca(OH)2. The findings showed that NaOH concentration, temperature, and stirring rate are the most significant process parameters. The addition of Ca(OH)2 facilitates the leaching of lithium and minimizes the concentration of silicate and fluoride in the leach liquor by forming solid phases identified as Ca3Al2Si3O12 CaF2 and NaCaHSiO4, with a loss of about 7% NaOH. The leaching efficiencies after 2 h were 94% Li, 98% K, 96% Rb, and 90% Cs under the most suitable conditions (250 °C, 320 g/L NaOH, liquid-to-solid ratio of 10, 300 rpm stirring speed, lime addition of 0.3 g/g). Precipitation of lithium as Li3PO4 by adding phosphoric acid and subsequent conversion of Li3PO4 to LiOH using Ca(OH)2 recovered 83% of lithium as LiOH allowing recycling the rest along with 93% of NaOH for leaching.
Lepidolite is an important mineral resource of lithium, rubidium and cesium. Lithium, rubidium and cesium were extracted simultaneously from a lepidolite concentrate by sulfuric acid baking and water leaching. A crystallization-roasting-dissolution-solvent extraction process was developed to recover cesium from the leach solution in this study. During crystallization, leach solution was cooled from 85 °C to 35 °C firstly to precipitate most parts of Rb+ with 98.65% and Cs+ with 94.59% in the form of RbAl(SO4)2·xH2O and RbAl(SO4)2·xH2O, respectively. The mixed alums were then roasted at 900 °C to decompose them into Cs2SO4, Rb2SO4, K2SO4 and Al2O3. Next, a mixed sulfates solution with 12.51 g/L Rb+ and 2.4 g/L Cs+ was obtained by water dissolution of the roasted alums. Cesium was then separated from the solution by solvent extraction, scrubbing and stripping. A Cs-loaded organic phase with 4.66 g/L Cs+ and 3.05 g/L Rb+ was obtained after a four-stage countercurrent extraction. Around 99.20% of Cs+ and 10.44% of Rb+ were extracted by using 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP). After scrubbing and stripping of the Cs-loaded organic phase by diluted H2SO4, a cesium sulfate solution of 16.6 g/L Cs+ was obtained. A cesium sulfate product with a purity of 98.47 wt% was then recovered by evaporation and crystallization of the stripping solution
Lepidolite is a precious multi-metal resources of lithium, rubidium, cesium and potassium. A chlorination process for efficient co-extraction of Li, Rb, Cs and K from lepidolite concentrate was investigated in this study. The lepidolite concentrate was roasted with a mixed chlorination agent of CaCl2 and NaCl at moderately high temperature followed by water leaching. The following optimal process conditions were identified: mass ratio of 30% CaCl2 and 20% NaCl to lepidolite concentrate, roasting temperature of 750 ºC, roasting time of 45 min, water leaching temperature of 25 ºC and liquid-to-solid ratio of 3:1. Under the optimal conditions, the extraction efficiencies of Li, Rb, Cs and K reached 92.49%, 98.04%, 98.33% and 92.90%, respectively. During chlorination roasting, the alkali metals in the lepidolite were transformed into water soluble chloride salts, along with the generation of insoluble phases, such as CaAl2Si2O8, CaF2 and NaAlSi3O8. After water leaching, a leachate with 5.15 g/L Li and few impurities such as aluminum was obtained, which was beneficial for subsequent leachate purification and metals recovery. This chlorination process is technologically feasible and potential for practical application.
The treatment of lepidolite by a multistage leaching process was studied for the extraction of alkali metals as alkali alums and brines. The precipitation characteristics of the aluminum and fluorine in the solution were also investigated. The transformation of the mineralogical species in lepidolite into albite and silicon dioxide was tentatively identified by X-ray diffraction measurements. The crystallization was aimed at the separation of rubidium and cesium from an acidic solution containing potassium as the main contaminant. The alum mixture contained on average 7.5% potassium, 1.3% rubidium and 0.30% cesium. The main crystalline components were aluminum sulfate and AlF(SO4)·5H2O after concentration. The aluminum in the solution was removed by adding potassium sulfate with a K/Al mole ratio of 2 at various pHs to yield an overall aluminum precipitation of 62.1–66.6%. Under weakly acidic and neutral conditions, soluble aluminum may transform into insoluble aluminum, such as Al(OH)3. Additionally, soluble AlFx(3−x)+ species tended to precipitate directly with OH⁻, thereby achieving the formation of Al-OH-F complexes. The AlFx(3−x)+ species at high pH were partially dissociated into F⁻ and AlOH²⁺, Al(OH)2⁺ and Al(OH)4⁻, and the buffering effect of F⁻ inhibited the transformation of the precipitated Al(OH)3 into soluble aluminates due to the formation of Al-OH-F complexes. The residual aluminum and fluorine contents were on average 0.0065 g/L and 0.042 g/L, respectively, in the mother liquor after neutralization at pH 9. The loss of lithium increased from 1.1% to 5.4% as the pH increased from 5 to 9. These findings imply that aluminum and fluorine can play significant roles in the recovery of alkali metals from lepidolite, and the precipitation of aluminum from leaching solutions as alums can cause a loss of lithium.
This research reports an innovative boron adsorbent of CA@KH-550@EPH@NMDG (CKEN) via the modification of N-methyl-d-glucosamine (NMDG) on the surface of biomass carbonaceous aerogel, which is environmentally friendly, economically inexpensive, has simple preparation process and good regenerability. SEM and FT-IR characterization results indicate that CKEN has a 3D cross-staggered structure with lots of hydroxyl groups and pore structure, which are beneficial to the diffusion of boron and the chelation interaction between boron and CKEN. The adsorption behavior of CKEN for boron was evaluated. Various parameters affecting adsorption properties, viz., pH, ionic strength, initial concentration of boron, temperature and contact time were investigated. The adsorption kinetics is fitted with pseudo-second-order kinetics model better and the adsorption of boron on CKEN is an exothermic process. The adsorption equilibrium reached within 15 h with the maximum adsorption amount of 1.42 mmol/g (298 K). Moreover, CKEN also showed excellent reusability by consecutive five cycles of adsorption-desorption. It can be used as a potential recyclable adsorbent for efficient enrichment of boron from aqueous solution.
Respirable sintering dust was an abundant and hazardous waste arrested by electrostatic precipitators from iron and steel industry. In this study, this waste was first found to contain 0.3% Rb, existing in the form of chloride and making it a promising Rb extracting material. Meanwhile, 95.24% of Rb and 93.43% of K in it can be easily recovered by water leaching (S/L = 1:5), resulting in a solution of 740 mg/L Rb and 33.85 g/L K. Then this leachate was extracted with 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP) in sulphonated kerosene to separate Rb from K after purification. The optimized solvent extraction conditions were 1.0 mol/L t-BAMBP, phase ratio of 3:1, 1.2 mol/L alkalinity in aqueous. Moreover, the organic phase was treated with deionized water (O/A = 5:1) for scrubbing and 1.2 mol/L HCl (O/A = 5:1) for stripping. Under optimal conditions, a single Rb extraction and back-extraction efficiencies were 91.80% and 89.93%, respectively. Finally, a RbCl with 99.5% purity and a total Rb extraction rate of 58.26% were achieved by a multistage continuous countercurrent extraction. These results did not only indicate that respirable sintering dust is a new tremendous potential Rb source but also provide a promising way to utilize Rb from this dust.
Materials capable of separating and removing iodine ions (I-) from aqueous solution are of significance to our society, especially human health. Adsorption is one of the effective I- separation methods. In the present work, a novel biomass carbonaceous aerogel (CA) modified with 3-glycidyl-oxypropyl-trimethoxy-silane (KH-560) was prepared and used for I- adsorption for the first time. This preparation process of CA@KH-560 is easily accessible. The results of characterizations demonstrated that CA and CA@KH-560 have three-dimensional porous structure with the sheet like skeletons connected to each other, and KH-560 effectively entered into the matrix of CA. Adsorption experiments were carried out systematically by changing pH, adsorption time, ionic strength, temperature and ion concentration. The maximum adsorption capacity for I- is 2.5 mmol/g at initial pH of 1.5. The adsorption can reach equilibrium within 24 h and the data of adsorption kinetics fitted the pseudo-second-order model very well. The adsorption isotherm model Langmuir, Freundlich, and Tempkin isotherms were studied, and the results showed that the Langmuir model is the best-fitting one for the experimental results. Moreover, CA@KH-560 shows excellent regenerating ability and the regeneration process is relatively simple.
Engelhard Titanosilicate-10 (ETS-10) has been studied widely for its adsorption and photocatalytic properties. The properties can be enhanced through various chemical approaches, such as modification of ETS-10 active sites with transition metal. In this work, graphene oxide incorporated ETS-10 (as GO/ETS-10) was prepared by refluxing the ETS-10 powder and GO suspension in water medium. The obtained GO/ETS-10, as revealed by X-ray photoelectron spectroscopy (XPS), was chemically bound through the carbon atoms of GO and the oxygen atoms on the surface of ETS-10. The GO/ETS-10 composite has shown exceptional adsorption properties towards cationic methylene blue (MB⁺) in comparison to ETS-10 alone. However, results have shown that the GO/ETS-10 has poor adsorption affinity towards anionic methyl orange (MO–) in water. The adsorption isotherms of GO/ETS-10 composite towards MB⁺ was best fitted to the Langmuir isotherm with maximum adsorption capacity of 285 mg/g which was about 2 times higher than adsorption capacity of ETS-10 alone, i.e. 135 mg/g. Besides, adsorption kinetics of GO/ETS-10 was best fitted to the pseudo-second order model revealing that the chemisorption was dominant throughout the adsorption process. Considering the nature of GO/ETS-10 that is composed from less harmful elements, it has good potential in the environment remediation, such as water and air purification, with a good selectivity toward cationic molecules.
Impedance spectroscopy was used to investigate the long-range ionic conductivity of the microporous, titanosilicate (Na,K)-ETS-10 and ion-exchanged Mⁿ⁺-ETS-10 (where, Mⁿ⁺ = Li⁺, Na⁺, Mg²⁺, Zn²⁺, Ca²⁺) thin films prepared by secondary growth method. To figure out the effect of grain boundary on ionic conduction, as-synthesized (Na,K)-ETS-10 films possessing different thicknesses of columnar grain structure (i.e., films prepared via 4h-, 6h-, 8h-, and 10h-growth) were tested. The conductivities of the films with different thicknesses at 723 K were in the range of ∼10⁻³ Ω⁻¹cm⁻¹. However, activation energies of the films decreased from 52.8 to 47.3 kJ mol⁻¹ (i.e., 0.6 to 0.5 eV) for 4h-(Na,K)-ETS-10 to 10h-(Na,K)-ETS-10 films, respectively. The as-synthesized (Na,K)-ETS-10 film prepared via 6h-growth (denoted as (Na,K)-6h-ETS-10) and monovalent cation-exchanged samples Li- and Na-6h-ETS-10 films exhibit conductivities of 2.1 × 10⁻³, 2.4 × 10⁻⁴, and 2.7 × 10⁻⁴ Ω⁻¹cm⁻¹, respectively, at 723 K and activation energies of 50.1, 55.5, and 55.4 kJ mol⁻¹, respectively, in the temperature range 573–773 K. Divalent cation-exchanged samples Mg-, Zn- and Ca-6h-ETS-10 films exhibit conductivities of 2.3 × 10⁻⁴, 2.9 × 10⁻⁴, and 8.8 × 10⁻⁵ Ω⁻¹cm⁻¹, respectively, at 723 K and activation energies of 62.5, 57.9, and 65.2 kJ mol⁻¹, respectively, in the temperature range 573–773 K. The data shown here indicate that ionic conductivity of intergrown (Na,K)-ETS-10 films prepared by secondary growth method were significantly enhanced with respect to pressed pellets of powder zeolite and zeo-type materials which imply the importance of engineering the microstructure of the zeolite film to improve the conductivity of zeolites and zeo-type materials.
The residues of salt lake brine from which potassium had been removed were used to extract Rb+ and Cs+ together with a sulphonated kerosene (SK) solution of 1.0 mol/L 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP). Rb+ and Cs+ were enriched and separated effectively by precipitating Mg2+ before extraction and by scrubbing out K+ and Na+ repeatedly before stripping. The effects of the volume ratio of organic phase to aqueous extraction phase (O/A), alkalinity of aqueous phase (c(OH)−), interference from K+ and Mg2+, and ratio the volume of organic phase to aqueous scrubbing phase (O/A′) were investigated. The experimental brine was extracted optimally by 5-stage extraction with 1.0 mol/L t-BAMBP in SK, c(OH−)=1 mol/L, and O/A=1:1. The scrubbing yield of rubidium was only about 10.5% when the extraction solvent was washed 3 times with 1×10−4 mol/L NaOH at O/A′=1:0.5. After 5-stage countercurrent extraction, the final extraction yields of Rb+ and Cs+ reached 95.04% and 99.80%, respectively.
In this work, a composite spherical adsorbent, which employs potassium titanium silicate as an adsorption active component, and calcium alginate as a carrier, was successfully prepared. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the adsorbent. The kinetics and thermodynamics of rubidium and cesium ions adsorption were investigated comprehensively, by considering the effects of initial concentration, temperature, solution pH, and coexisting NaCl. According to the determination coefficients, the pseudo second-order kinetic model provided an impressive and comparable correlation, and the second-order rate constant and the initial adsorption rate increase with increasing temperature. In general, the equilibrium adsorption amount increases with the increasing initial metal ion concentration, but decreases with increasing coexisting NaCl. The adsorption capacity keeps constant in the pH value range 3-12 and slightly fades when the temperature increases from 25 to 55 degrees C. Under similar conditions, rubidium and cesium show the similar adsorption amount. The adsorbent has a fast adsorption rate and an adsorption capacity of about 1.55 mmol g(-1) for rubidium and 1.47 mmol g(-1) for cesium when the initial metal ion concentration is 0.10 mol L-1. The composite adsorbent is effective for the adsorption of rubidium or cesium ions from simulated brines.
Chlorination roasting followed by water leaching process was used to extract lithium from lepidolite. The microstructure of the lepidolite and roasted materials were characterized by X-ray diffraction (XRD). Various parameters including chlorination roasting temperature, time, type and amount of chlorinating agents were optimized. The conditional experiments indicate that the best mass ratio of lepidolite to NaCl to CaCl2 is 1:0.6:0.4 during the roasting process. The extraction of lithium reaches peak value of 92.86% at 880 °C, potassium, rubidium, and cesium 88.49%, 93.60% and 93.01%, respectively. The XRD result indicates that the major phases of the product after roasting lepidolite with mixture of chlorinating agents (CaCl2 and NaCl) are SiO2, CaF2, KCl, CaSiO3, CaAl2Si2O8, NaCl and NaAlSi3O8.
Supported ruthenium catalysts have been shown to be effective for the dry reforming of methane. Besides, ETS-10 titanosilicate has properties able to disperse Ru species. In this work, microporous ETS-10 titanosilicate was synthesized by hydrothermal synthesis employing anatase as Ti source. Ru was incorporated using three different methods: by incipient wetness impregnation (RuH), by ion exchange (RuI) and by adding Ru to the gel synthesis (RuG). The species present in the solids were characterized by XRD, N2 adsorption, ICP, SEM, TEM, EDX, TGA, TPR, UV–vis and XPS.RuH and RuI catalysts were found to be active and stable for the dry reforming of methane. These results show the potential application of ETS-10 as support of Ru catalysts for the production of hydrogen.
Twisted carbon fiber (TCF) aerogel with good selective sorption is produced in large scale by using raw cotton as the precursor. TCF aerogel shows highly efficient sorption of organic liquids (pump oil: up to 192 times its own weight; chloroform: up to 115 times its own weight). Moreover, it could be regenerated many times without decrease of sorption capacity by distillation, combustion or squeezing, which depends on the type of pollutants.
In the present work, the local structure changes of microporous titanosilicate ETS-10 upon treatment with citric acid, phosphoric acid, and nitric acid were characterized using XRD, FTIR, Raman, XPS, DR-UV, 29Si MAS NMR, and 1H−29Si CP MAS NMR techniques. The experimental results suggested that regardless of the nature of the acids, the replacement of alkali cations by protons altered the local structure of ETS-10 solid, including partial dissolution of the siliceous matrix and leaching of titanium species from the TiO6 chains. In the meantime, it was observed that the hexacoordinated Ti species of ETS-10 were changed to penta- and/or tetracoordinated ones, generating terminal TiOH groups, accounting for the observed enhancement of photodegradation activity of the acid-treated ETS-10 materials toward phenol compounds.
A new hydrous crystalline silicotitanate (CST), which the authors call TAM-5, has been synthesized that selectively removes cesium cations from solutions containing up to 5.7 M Na[sup +] and for a pH range of less than 1 to greater than 14. In basic media and at the high concentrations of Na[sup +] the CST also removes strontium cations from the solution. For a solution containing 5.7 M Na[sup +], 0.6 M OH[sup [minus]], 5.1 M NO[sub 3][sup [minus]], 100 mg/l Cs[sup +], and 20 mg/l Sr[sup 2+], the distribution coefficients for cesium and strontium are 1,000 ml/g and greater than 4,000 ml/g, respectively. For a solution of 5.7 M NaNO[sub 3], 100 mg/l Cs[sup +] and 20 mg/l Sr[sup 2+] the distribution coefficient for cesium is greater than 10,000 ml/g and for strontium it is equal to 200 ml/g. Experimental studies have also been conducted using complex waste simulants, which compare the performance of this CST and up to 60 other potential ion exchangers/absorbents. These studies substantiate the high selectivity of the CST for cesium in acidic and basic solutions. This new CST, labeled TAM-5, has considerable potential for removing cesium and strontium from defense wastes.
A composite spherical adsorbent was prepared with ammonium molybdophosphate (AMP), sodium alginate (NaALG), and calcium chloride. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the composite adsorbent. The adsorption of rubidium and cesium ions onto the composite adsorbent in aqueous solutions was investigated comprehensively by varying the initial metal ion concentration, pH, ionic strength, and temperature. The adsorption kinetics of both rubidium and cesium was described by the first-order and second-order kinetic models. The second-order rate constant and the initial adsorption rate increase with increasing temperature. In general, the equilibrium adsorption amount of both rubidium and cesium increases with the increase in initial metal ion concentration, but decreases with increasing ionic strength and temperature. Maximum adsorption of rubidium and cesium occurs in the solution with an equilibrium pH value of 3.5–4.5. Under similar conditions, cesium shows a higher adsorption amount than rubidium. The composite adsorbent is easy to prepare and highly porous. It has a fast adsorption rate and an adsorption capacity of 0.58 and 0.69 mmol g−1 for rubidium and cesium, respectively. The composite adsorbent is effective for the adsorption of rubidium or cesium ions from solutions containing some other alkali metal ions, such as sodium ions.
Adsorption equilibrium is calculated for slit-like pores of various sizes using lattice density functional theory (LDFT). It is shown that LDFT can predict adsorption isotherms with hysteresis loops and that different types of hysteresis loops can be obtained by varying energies of adsorbate–adsorbate and adsorbate–adsorbent interactions for different widths and lengths of slit-like pores. LDFT also predicts hysteresis loops with multiple steps. Though such behavior has not been part of the characterization of isotherms with hysteresis loops, there are experimental data that exhibit steps within hysteresis loops.
A new hybrid gel with boron-selective functional groups is prepared with tetraethoxysilane (TEOS), (3-glycidoxypropyl)trimethoxysilane (GPTMS), and a new precursor (W) synthesized from GPTMS and N-methylglucamine (MG). We investigate the boron adsorption onto the hybrid gel and the commercial resin D564 in aqueous solution by varying the initial boron concentration, pH, ionic strength, and temperature. Adsorption of both the hybrid gel and the D564 can be described by the second-order kinetics and the hybrid gel shows the lower second-order rate constant and the initial adsorption rate than the commercial resin. A maximum boron adsorption occurs at pH 4–9, which can be explained by the adsorption suppression by H+ ions at low pH and the weakened complexation by electrostatic repulsion at high pH. Ionic strength of the solution affects both the adsorption kinetics and thermodynamics, and it has a more pronounced effect on the kinetics of the hybrid gel than the D564. For both the hybrid gel and the D564, adsorption was found to be a chemisorption, which may be more advantageous in removal of boron from water than physisorption due to a higher adsorption capacity and better selectivity. Compared with other boron-selective adsorbents, the boron-selective hybrid gel in this study is easy to prepare, and has a good mechanical strength and an adsorption capacity (1.15 mmol g−1).
Nitrogen-doped graphene (N-graphene) is obtained by exposing graphene to nitrogen plasma. N-graphene exhibits much higher electrocatalytic activity toward oxygenreduction and H2O2 reduction than graphene, and much higher durability and selectivity than the widely-used expensive Pt for oxygenreduction. The excellent electrochemical performance of N-graphene is attributed to nitrogen functional groups and the specific properties of graphene. This indicates that N-graphene is promising for applications in electrochemical energy devices (fuelcells, metal–air batteries) and biosensors.
The effect of cesium therapy on various cancers is reported. A total of 50 patients were treated over a 3 year period with CsCl. The majority of the patients have been unresponsive to previous maximal modalities of cancer treatment and were considered terminal cases. The Cs-treatment consisted of CsCl in addition to some vitamins, minerals, chelating agents and salts of selenium, potassium and magnesium. In addition, a special diet was also instituted. There was an impressive 50% recovery of various cancers, i.e., cancer of unknown primary, breast, colon, prostate, pancrease, lung, liver, lymphoma, ewing sarcoma of the pelvis and adeno-cancer of the gallbladder, by the Cs-therapy employed. There was a 26% and 24% death within the initial 2 weeks and 12 months of treatment, respectively. A consistent finding in these patients was the disappearance of pain within the initial 3 days of Cs-treatment. The small number of autopsies made showed the absence of cancer cells in most cases and the clinical impression indicates a remarkably successful outcome of treatment.
Neuronal apoptosis plays a critical role in the pathogenesis of neurodegenerative disorders, and neuroprotective agents targeting apoptotic signaling could have therapeutic use. Here we report that cesium chloride, an alternative medicine in treating radiological poison and cancer, has neuroprotective actions. Serum and potassium deprivation induced cerebellar granule neurons to undergo apoptosis, which correlated with the activation of caspase-3. Cesium prevented both the activation of caspase-3 and neuronal apoptosis in a dose-dependent manner. Cesium at 8 mM increased the survival of neurons from 45 +/- 3% to 91 +/- 5% of control. Cesium's neuroprotection was not mediated by PI3/Akt or MAPK signaling pathways, since it was unable to activate either Akt or MAPK by phosphorylation. In addition, specific inhibitors of PI3 kinase and MAP kinase did not block cesium's neuroprotective effects. On the other hand, cesium inactivated GSK3beta by phosphorylation of serine-9 and GSK3beta-specific inhibitor SB415286 prevented neuronal apoptosis. These data indicate that cesium's neuroprotection is likely via inactivating GSK3beta. Furthermore, cesium also prevented H(2)O(2)-induced neuronal death (increased the survival of neurons from 72 +/- 4% to 89 +/- 3% of control). Given its relative safety and good penetration of the brain blood barrier, our findings support the potential therapeutic use of cesium in neurodegenerative diseases.