Sodium Ion Exchange Research Articles

Niobate nanofibers for simultaneous adsorptive removal of radioactive strontium and iodine from aqueous solution

Radioisotopes pose a potential mass threat to public heath if accidently released into the environment. To mitigate the consequences, effective methods must be developed for removal of radioactive ions from the environment. In this study, we show that nanofibers of sodium niobate with negatively charged layers and readily exchangeable sodium ions between the layers can efficiently remove radioactive Sr2+. The exchange of Sr2+ ions with the interlayer Na+ ions can cause structural deformation of layers, trapping the Sr2+ in the nanofibers. Furthermore, silver oxide (Ag2O) nanocrystals can be firmly anchored on the surface of niobate nanofibers via coherent interfaces between Ag2O and niobate phases. I− anions in fluids can easily access the Ag2O nanocrystals and be efficiently trapped by forming an AgI precipitate that firmly attaches to the adsorbent. This bi-functional absorbent can be arranged to remove Sr2+ and I− ions simultaneously by optimizing the Ag2O loading and Na+ content of the niobate nanofibers. It can provide high adsorption capacity for both ions in basic media, unlike other adsorbents that can be used in acid or neutral media. The maximum adsorption capacities of Sr2+ and I− for Ag2O anchored sodium niobate nanofibers were found to be 148.92 and 296 m2 g−1 respectively. Furthermore, the niobate adsorbents can be readily dispersed in liquids and easily separated after purification due to their fibril morphology, which significantly enhances their adsorption efficiency and reduces separation costs. This study demonstrates that Ag2O anchored sodium niobate nanofibers with fibril morphology, negatively charged thin layers and readily exchangers are potential sorbent for the simultaneous uptake of cations and anions.

Investigating the Factors for the Low Cycle Life of Sodium Oxygen Batteries

Metal air (oxygen) batteries have recently attracted extensive research attentions due to the high theoretical energy density. Compared to lithium oxygen batteries, sodium oxygen batteries have much lower charging overpotentials which may offer longer cyclability and higher energy efficiency without losing much energy density (~1100 Wh kg-1 vs. ~3460 Wh kg-1). However, the short cycle lives of sodium oxygen batteries greatly limit their applications in transportations or energy storage systems. The main reasons for the short cycling life of sodium oxygen batteries were primarily ascribed as the accumulation of by-product during discharge and charge processes and/or electrolyte degradation. However, in our studies, issues from the anode such as sodium dendrite formation and side reactions were ascribed to the major reasons for the short circuit of sodium oxygen batteries. By employing a sodium ion exchange Nafion membrane in separators, largely improved cyclability of sodium oxygen batteries was achieved by suppressing the penetration of dendrites formed during the charging process. After solving the deadly short circuit of sodium oxygen batteries by Nafion’s physically preventing effect, cycle lives of 118 cycles in dimethoxyethane (DME) based electrolytes and 80 cycles in bis(2-methoxyethyl) ether (diglyme) based electrolytes were achieved with a current density of 0.16 mA cm-2. The components of SEI layer on the sodium anode and by-product in the air electrode were identified. The sodium anode went through severe degradation process. It is proved that oxygen crossover was another factor to cause the failure of sodium oxygen batteries. These results highlight the significance of solving dendrite penetration and blocking oxygen crossover in sodium oxygen batteries and paved the way for further improving the performance and cyclability of batteries. Figure 1

Removal of uranium and fluorine from wastewater by double-functional microsphere adsorbent of SA/CMC loaded with calcium and aluminum

A novel dual functional microsphere adsorbent of alginate/carboxymethyl cellulose sodium composite loaded with calcium and aluminum (SA/CMC-Ca-Al) is prepared by an injection device to remove fluoride and uranium, respectively, from fluoro-uranium mixed aqueous solution. Batch experiments are performed at different conditions: pH, temperature, initial concentration and contact time. The results show that the maximum adsorption amount for fluoride is 35.98mg/g at pH 2.0, 298.15K concentration 100mg/L, while that for uranium is 101.76mg/g at pH 4.0, 298.15K concentration 100mg/L. Both of the adsorption process could be well described by Langmuir model. The adsorption kinetic data is fitted well with pseudo-first-order model for uranium and pseudo-second-order model for fluoride. Thermodynamic parameters are also evaluated, indicating that the adsorption of uranium on SA/CMC-Ca-Al is a spontaneous and exothermic process, while the removal of fluoride is non-spontaneous and endothermic process. The mechanism of modification and adsorption process on SA/CMC-Ca-Al is characterized by FT-IR, SEM, EDX and XPS. The results show that Ca (II) and Al (III) are loaded on SA/CMC through ion-exchange of sodium of SA/CMC. The coordination reaction and ion-exchange happen during the adsorption process between SA/CMC-Ca-Al and uranium, fluoride. Results suggest that the SA/CMC-Ca-Al adsorbent has a great potential in removing uranium and fluoride from aqueous solution.

Biosorption of uranium(VI) from aqueous solution using microsphere adsorbents of carboxymethyl cellulose loaded with aluminum(III)

The carboxymethyl cellulose microsphere loaded with Al(III) (CMC-Al) has been explored for removal of uranium(VI) from U-containing water. Various factors, including pH, adsorbent dosage and uranium(VI) concentration, were tested. Langmuir and Freundlich isotherms were applied to the adsorption data. The thermodynamic parameters such as ΔH°, ΔS° and ΔG° were also evaluated. The mechanism of modification and adsorption on CMC-Al were analyzed by SEM, EDX and XPS. Results show Al (III) was loaded on CMC through ion exchange of sodium ion of CMC. The coordination reaction happened during the adsorption process between CMC-Al and uranium(VI).

BDST modelling of sodium ion exchange column behaviour with strong acid cation resin in relation to coal seam water treatment

Reverse osmosis is the dominant technology utilized for desalination of saline water produced during the extraction of coal seam gas. Alternatively, ion exchange is of interest due to potential cost advantages. However, there is limited information regarding the column performance of strong acid cation resin for removal of sodium ions from both model and actual coal seam water samples. In particular, the impact of bed depth, flow rate, and regeneration was not clear. Consequently, this study applied Bed Depth Service Time (BDST) models to reveal that increasing sodium ion concentration and flow rates diminished the time required for breakthrough to occur. The loading of sodium ions on fresh resin was calculated to be ca. 71.1gNa/kg resin. Difficulties in regeneration of the resin using hydrochloric acid solutions were discovered, with 86% recovery of exchange sites observed. The maximum concentration of sodium ions in the regenerant brine was found to be 47,400mg/L under the conditions employed. The volume of regenerant waste formed was 6.2% of the total volume of water treated. A coal seam water sample was found to load the resin with only 53.5g Na/kg resin, which was consistent with not only the co-presence of more favoured ions such as calcium, magnesium, barium and strontium, but also inefficient regeneration of the resin prior to the coal seam water test.

Laboratory and field analysis of flowback water from gas shales

Flowback water is usually highly saline and the salt concentration varies by time and well location. Understanding the origin of the flowback salts is essential for evaluating fracturing and flowback processes. In this study, laboratory and field analyses are performed to investigate the origin of the flowback salts. The field data includes the total salt concentration (salinity), individual ion concentration, pH, and dissolved oxygen measured during the flowback process for three wells completed in the Horn River Basin. The rock mineralogy is determined using XRD. The cation exchange capacity (CEC) of shale samples are measured using ammonium acetate method. Water and oil imbibition experiments are conducted for shale samples of different surface-to-volume ratio. The individual ion concentration is measured during the water imbibition experiments using ICP–MS and IC. EDXS analysis is used to investigate the surface of natural fractures.Noticeable amount of barium found on the surface of natural fractures suggests that the barium in the flowback water primarily originates from the natural fractures. Furthermore, the samples with higher clay content have higher CEC. During the water imbibition process, these samples have higher and faster ion transfer from shale-to-water; suggesting the mobilization of the exchangeable ions from the clays. During the water imbibition experiment, the Na/Cl and K/Cl ratios are initially high and decrease at the later times. Leaching of the exchangeable sodium and potassium ions from the clay minerals is a possible reason for the initial high Na/Cl and K/Cl molar ratios. The dissolution of chloride-bearing components increases the chloride concentration, which decreases the Na/Cl and K/Cl molar ratios at later times. The measured pH is slightly above 8 for all of the flowback water samples. The presence of natural buffer systems such as calcite and dolomite may explain the neutral pH range of the flowback water.

Ion exchange of sodium chloride and sodium bicarbonate solutions using strong acid cation resins in relation to coal seam water treatment

Coal seam gas exploration has resulted in the production of large volumes of associated water which contains dissolved salts dominated by sodium chloride and sodium bicarbonate. Ion exchange using synthetic resins has been proposed as a method for desalination of coal seam water to make it suitable for various beneficial reuse options. This study investigated the behaviour of solutions of sodium chloride and sodium bicarbonate with respect to exchange with Lanxess S108H strong acid cation (SAC) resin. Equilibrium isotherms were created for solutions of NaCl and NaHCO3 and an actual sample of coal seam water from the Surat Basin in southern Queensland. The exchange of sodium ions arising from sodium bicarbonate was found to be considerably more favourable than exchange of sodium ions from sodium chloride solutions. This latter behaviour was attributed to the secondary decomposition of bicarbonate species under acidic conditions which resulted in the evolution of carbon dioxide and formation of water. The isotherm profiles could not be satisfactorily fitted by a single isotherm model such as the Langmuir expression. Instead, two Langmuir equations had to be simultaneously applied in order to fit the sections of the isotherm attributable to sodium ion exchange from sodium bicarbonate and sodium chloride. The shape of the isotherm profile was dependent upon the ratio of sodium chloride to sodium bicarbonate in solution and there was a high degree of correlation between simulated and actual coal seam water solutions.

Behaviour of natural zeolites used for the treatment of simulated and actual coal seam gas water

Coal seam gas operations produce significant quantities of associated water which often require demineralization. Ion exchange with natural zeolites has been proposed as a possible approach. The interaction of natural zeolites with solutions of sodium chloride and sodium bicarbonate in addition to coal seam gas water is not clear. Hence, we investigated ion exchange kinetics, equilibrium, and column behaviour of an Australian natural zeolite. Kinetic tests suggested that the pseudo first order equation best simulated the data. Intraparticle diffusion was part of the rate limiting step and more than one diffusion process controlled the overall rate of sodium ion uptake. Using a constant mass of zeolite and variable concentration of either sodium chloride or sodium bicarbonate resulted in a convex isotherm which was fitted by a Langmuir model. However, using a variable mass of zeolite and constant concentration of sodium ions revealed that the exchange of sodium ions with the zeolite surface sites was in fact unfavourable. Sodium ion exchange from bicarbonate solutions (10.3g Na/kg zeolite) was preferred relative to exchange from sodium chloride solutions (6.4g Na/kg zeolite). The formation of calcium carbonate species was proposed to explain the observed behaviour. Column studies of coal seam gas water showed that natural zeolite had limited ability to reduce the concentration of sodium ions (loading 2.1g Na/kg zeolite) with rapid breakthrough observed. It was concluded that natural zeolites may not be suitable for the removal of cations from coal seam gas water without improvement of their physical properties.

Factors influencing kinetic and equilibrium behaviour of sodium ion exchange with strong acid cation resin

This study reports an investigation of the ion exchange treatment of sodium chloride solutions in relation to use of resin technology for applications such as desalination of brackish water. In particular, a strong acid cation (SAC) resin (DOW Marathon C) was studied to determine its capacity for sodium uptake and to evaluate the fundamentals of the ion exchange process involved. Key questions to answer included: impact of resin identity; best models to simulate the kinetics and equilibrium exchange behaviour of sodium ions; difference between using linear least squares (LLS) and non-linear least squares (NLLS) methods for data interpretation; and, effect of changing the type of anion in solution which accompanied the sodium species. Kinetic studies suggested that the exchange process was best described by a pseudo first order rate expression based upon non-linear least squares analysis of the test data. Application of the Langmuir Vageler isotherm model was recommended as it allowed confirmation that experimental conditions were sufficient for maximum loading of sodium ions to occur. The Freundlich expression best fitted the equilibrium data when analysing the information by a NLLS approach. In contrast, LLS methods suggested that the Langmuir model was optimal for describing the equilibrium process. The Competitive Langmuir model which considered the stoichiometric nature of ion exchange process, estimated the maximum loading of sodium ions to be 64.7 g Na/kg resin. This latter value was comparable to sodium ion capacities for SAC resin published previously. Inherent discrepancies involved when using linearized versions of kinetic and isotherm equations were illustrated, and despite their widespread use, the value of this latter approach was questionable. The equilibrium behaviour of sodium ions form sodium fluoride solution revealed that the sodium ions were now more preferred by the resin compared to the situation with sodium chloride. The solution chemistry of hydrofluoric acid was suggested as promoting the affinity of the sodium ions to the resin.

The effect of electron beam irradiation on silver–sodium ion exchange in silicate glasses

It is shown experimentally that electron irradiation of sodium–silicate glasses makes possible the control of the subsequent ion exchange Ag+↔Na+ process in a salt melt. The reason of this effect is the negatively charged regions formation in a glass volume during electron irradiation. The electric field, produced by these regions in glass volume, results in positive Na+ ions field migration into them. The spatial redistribution of Na+ ions results in the decrease of the ion exchange efficiency, or the ion exchange can be even blocked. This led to the decrease of the luminescence intensity of neutral silver molecular clusters in the irradiated zone, and effect on the silver nanoparticles formation during the subsequent thermal treatment. The observed effects can be used for the control of ion exchange processes during integrated optics devices fabrication, and for the electron-beam recording of optical information.

Assessment of the vacuolar Na+/H+ antiporter (NHX1) transcriptional changes in Leptochloa fusca L. in response to salt and cadmium stresses.

Sodium/proton exchangers (NHX) are key players in plant responses to salinity and have a central role in establishing ion homeostasis. NHXs can be localized in tonoplast or plasma membranes, where they exchange sodium ions for protons, resulting in the removal of ions from the cytosol into vacuole or extracellular spaces. In the present study, the expression pattern of the gene encoding Na+/H+ antiporter in the vacuolarmembrane (NHX1 gene) in Leptochloa fusca (Kallar grass) was measured by a semi- quantitative RT-PCR method under different treatments of NaCl and CdCl2. Results indicated that NaCl positively affected expression levels of LfNHX1, and that the amount of LfNHX1 mRNA increased in conjunction with the rise of salinity pressure, This finding suggests that vacuolar Na+/H+ antiporter might play an important role in the salt tolerance ability of kallar grass. The results also showed that cadmium exposure significantly modulated the mRNA expression of the LfNHX1 gene, suggesting that cadmium exposure disturbed Na+ homeostasis across the tonoplast and decreased the salt tolerance ability of kallar grass.

Mechanical Properties of Photomultiplier Tube Glasses for Neutrino Detection

Photomultiplier tubes (PMT) are one of the primary components of water Cherenkov neutrino detection for the Long Baseline Neutrino Experiment (LBNE). Thousands of 10‐ to 12‐inch diameter PMT bulbs are placed in the inner wall of a detection tank or a reservoir (e.g., deep mine) filled with 10,000 gallons of high purity water with a resistivity of 11–18.24 MΩ‐cm. Long‐term service of PMTs is vital to the success of neutrino detection projects. We report our results of our investigation on mechanical properties of PMT glasses from two vendors and the effect of ion exchange on their mechanical strength. Vickers indentation, four‐point bend test, and ring‐on‐ring biaxial flexural strength test were used for evaluation of the mechanical strength. Chemical (potassium–sodium ion exchange) strengthening results show increased strength of 46% in one vendor glass and a 57% increase in the other, with no significant reduction in optical transmission in the ultraviolet‐visible range of the electromagnetic spectrum that is critical to neutrino detection. Our results also show narrowing of the distribution of strength calculated using Weibull statistics with chemical strengthening for comparable exchange depths of 22–28 μm.

Flue gas desulfurization gypsum application for enhancing the desalination of reclaimed tidal lands

Soil desalination of estuary wetlands by the natural processes of rainfall leaching and plant community succession requires several decades for complete remediation. We hypothesize that flue gas desulfurization (FGD) gypsum can be used as a soil amendment to accelerate the desalination process via calcium ions (Ca2+) replacing exchangeable sodium (Na+) ions. Field experiments in reclaimed tidal lands in the Yangtze River delta were conducted with FGD gypsum applied at concentrations of 0, 15, 30, 45, and 60Mgha−1 during the period of 2011–2013. The total salt content of the topsoil (0–30cm) was approximately 10g/kg and the average rainfall at this site during the experimental period was 1000mm. The dominant halophytes were Phragmites australis and Spartina alterniflora. After one year of FGD gypsum treatment, salt content of the topsoil represented as exchangeable sodium percentage (ESP) was reduced by up to 50%. Species richness and the coverage of herbaceous plants, other than P. australis and S. alterniflora, increased with increasing rates of FGD gypsum (P<0.05). Halophytic herbs such as Suaeda glauca, Herba taraxaci, and Artemisia lavandulaefolia as well as the non-halophytic species Medicago sativa and Alternanthera philoxeroides were observed in the gypsum treated areas. In the plots treated with 45 and 60Mgha−1 of FGD gypsum, survival rates of woody plants were significantly higher than in the plots with lower treatment levels (P<0.05). FGD gypsum increased the amount of Ca on the soil cation exchange sites which resulted in enhanced salt leaching efficiency, plant diversity, and succession. FGD gypsum is readily available and can be applied on a large scale to promote the rapid and effective remediation of the saline soil in reclaimed tidal lands.

Custom Designed Fabrication

AbstractThe silver sodium ion exchange process is a versatile and flexible technique for realizing high quality refractive microoptical elements with a high degree of freedom in design. An accurate mask technique allows for implementing a huge variety of optical functions, such as micro lens arrays with 100 % filling factor, custom designed micro lenses with different optical parameters (i. e. focal length, Numerical Aperture, sphericity, etc.) within the same array or beam shaping elements such as vortex elements. The article shows actual results and applications of these elements.

Effects of Ion Exchange on the Mechanical Properties of Basaltic Glass Fibers

Basaltic glass fibers with different lithium oxide (6–14 mol%) and sodium oxide (2–14 mol%) contents were prepared. The influence of Li2O and Na2O content on the process of fiber manufacturing was investigated. Addition of alkali oxides reduced the forming temperature and substantially expanded the fiber‐forming temperature ranges. The obtained thermal data from differential thermal analysis revealed a decline in glass transition temperature (Tg) of fibers against the compositional changes. The inclusion of Li2O and Na2O in the glass network led to a reduction in its thermal stability. The obtained X‐ray diffraction patterns and IR spectra of Li‐rich and Na‐rich basaltic glass fibers confirmed the formation of highly polymerized structures such as LiAl(Si2O6) and (Na,K)(AlSiO4), respectively, and relatively depolymerized silicate anions. The effects of potassium–lithium and potassium–sodium ion exchange on the mechanical properties of basaltic glass fibers were investigated. As‐received Li‐rich and Na‐rich basaltic glass fibers were ion‐exchanged in potassium nitrate for different exchange times, and their mechanical properties were measured before and after chemical tempering. The measured tensile strength and Young's modulus values of the fibers showed an increase after treatment in molten salt.

Enhanced Charge Transport and Storage of Two-Dimensional Vanadium Pentoxide

Atomically thin two-dimensional (2D) materials have a number of key features for electrochemical charge storage including significant available surface area, quantum confinement in two dimensions, and distinct local structures (e.g. surface states, edge sites). Vanadium pentoxide (V2O5) is a useful charge storage material based on its multiple available oxidation states which allows the material to store multiple ions and electrons within its structure during electrochemical cycling. V2O5 has a high theoretical specific capacity of 294 mAh/g based on the two-electron charge storage process, and this capacity is significantly higher than the capacity of current commercial cathode materials (~160 mAh/g). However, typical forms of V2O5 exhibit severe capacity fading upon cycling. We have explored 2D forms of V2O5 to provide cathode materials with high capacities and improved cycling stability. Two-dimensional V2O5 nanosheets were prepared from drying suspensions of ion-exchanged sodium metavanadate solutions. The synthesis, structural characterization, and electrochemical testing of 2D V2O5 will be presented to show the effect of various parameters (e.g. composition, particle size, aggregation, orientation) on the electrical and electrochemical properties. The ability to control the structure and properties of 2D materials allows the development of improved charge transport and storage materials for batteries, supercapacitors, and other electrochemical applications.

Effects of copper ions on the near-infrared luminescence in Bi doped silicate glass via copper for sodium ion exchange

The copper (Cu) atoms were incorporated into the bismuth (Bi) doped silicate glasses by the copper for sodium (Cu–Na) ion exchange method. After the ion exchange process, the Cu ions were introduced into the glass matrix with different copper valence states, namely, Cu0, Cu+, and Cu2+. Bi3+ ions could be reduced to lower valence states of Bi containing Bi near infrared (NIR) active centers with the incorporation of the Cu ions, resulting in the enhancement of the Bi NIR luminescence intensity. During the heat treatment process, some lower valence states of Bi containing Bi NIR active centers could be oxidized, resulting in the attenuation of the NIR luminescence of Bi. Our research may extend the understanding of chemical environment modulation in Bi valence states and offer a valuable way to enhance the NIR luminescence intensity of Bi in glasses.

Grazing incidence small angle X-ray scattering study of silver nanoparticles in ion-exchanged glasses

The size and distribution of silver nanoparticles in ion-exchanged silicate glass induced by thermal treatments in air at different temperatures were investigated by means of grazing incidence small angle X-ray scattering technique, X-ray diffraction and optical absorption spectra. Silver–sodium ion exchange of soda-lime silicate glasses was done at 350°C for 240min, then the samples were treated by thermal annealing in air at different temperatures 400, 500 and 550°C, respectively, for 1h. After the annealing treatment above 400°C for 1h, smaller Ag nanoparticles occurred, together with bigger ones. Both dissolution of smaller Ag nanoparticles and diffusion of larger ones are discussed in these stages of annealing in this contribution.

Stabilization treatment of a dispersive clayey soil using granulated blast furnace slag and basic oxygen furnace slag

Dispersive clays may pose considerable distress if not adequately taken care of. On the other hand, the treatment of problematic soils with waste materials has been recently proved to be a useful option from economic and environmental view point. Hence, in this research, the potential use and effectiveness of dispersive soil stabilization using two types of industrial by-product, including granulated blast furnace slag (GBFS) and basic oxygen furnace slag (BOFS) were investigated. The slags were separately added (ranging from 2.5 to 30%) to a laboratory dispersed sample and a set of experiments were performed to study the physicochemical, mechanical and microstructural changes of the stabilized soil. The results indicate that the soil dispersion can be eliminated upon adding 10% BOFS. This is attributed to the exchange of interlayer sodium ions on the clay surfaces by multivalent cations from the agent. Besides, an increase in the ion concentration of soil-additive mixtures induces a more depression of the diffuse double layer that decreases the soil dispersivity potential. With increasing the curing time, an improvement in the strength of composite samples is observed. The formation of cementitious compounds due to the pozzolanic reactions is responsible for such a treatment, as confirmed by the XRD analyses and SEM micrographs. It appears that the GBFS has a lower activity as compared to BOFS, therefore causes less influence on the soil engineering parameters and a higher percentage (20–25%) of GBFS is required to govern soil dispersion. Overall, utilization of the studied slags particularly of BOFS is very effective to overcome the problems associated with dispersive soils.

Synthesis and metal ion sorption properties of peroxide-modified sodium titanate materials using a coprecipitation method

Peroxide-modified sodium titanate is synthesized by a coprecipitation method that uses titanium isopropoxide and sodium hydroxide precursors, with hydrogen peroxide as a mineralizer to modify the titanate to enhance actinide sorption. The mechanism and microstructure of the peroxide-modified titanate, synthesized using hydrogen peroxide at various pH values, and the effect on the sorption capacity of metal ions were studied. In the pH range of 8–9, the product experiences a highest weight loss of 34%, as well as the smallest sodium content and ion exchange capacity. In contrast, in the pH range of 6–7, the highest metal ion exchange ability is noted, up to 170mg/g. The pH value is crucial for the synthesis of peroxide-modified titanate materials.