Conventional Ion Exchange Research Articles

Determination of 90Sr in highly radioactive aqueous samples via conversion to a kinetically stable 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex followed by concentration–separation–fractionation based on capillary electrophoresis–liquid scintillation

BackgroundThe Fukushima Daiichi Nuclear Power Plant accident (2011) released large amounts of radioactive substances into the environment and generated highly radioactive debris. Post-accident countermeasures are currently in the phase of fuel debris removal, which requires the analysis of radioactive contaminants in the environment and fuel. The spectra of solely β-emitting nuclides, such as 90Sr, overlap; thus, an effective method for nuclide separation is desired. Since conventional methods for high-dose sample analysis pose substantial exposure risks and generate large amounts of secondary radioactive waste, faster procedures allowing for decreased radiation emission are highly desirable. ResultsIn this study, we developed a 90Sr2+ quantitation technique based on liquid scintillation counting (LSC)–coupled capillary transient isotachophoresis (ctITP), along with two-point detection and relying on the rapid concentration, separation, and fractionation of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-complexed 90Sr2+ in a single run. The applicability of our method for the analysis of real-world samples was verified by conducting addition-recovery experiments using a seawater reference material and radioactive liquid waste obtained from the radioactive waste treatment facility at the Japan Atomic Energy Agency. The recovery determined by LSC was 95–113%, indicating successful quantitative analysis. 90Sr recovery was determined to be 90.1% from a contaminated water sample obtained from the Fukushima Daiichi Nuclear Power Plant, which was analyzed using the standard addition of 90Sr. The sensitivity (detection limit = 0.016 Bq) of the proposed method on a radioactivity basis was equal to or higher than that of the conventional method using ion exchange-LSC (0.012–0.07 Bq). Significance and noveltyOur method allows for the handling of high-dose radioactive samples at the microliter level and is substantially faster than conventional ion exchange protocols, whereas ctITP has not been used for practical applications due to inaccurate collection and lack of a suitable chemical system. The concentration–separation–fractionation protocol in ctITP is successful due to the existence of a rare inert Sr2+ complex and precise fractionation. This study establishes a pathway toward safer and more practical analysis of radionuclides.

Rapid determination of chromium species in environmental waters using a diol-bonded polymer-stationary column under water-rich conditions coupled with ICPMS.

Chromium speciation analysis in environmental water is of great significance for the monitoring of water pollution and assessing its influences on human health. This study proposes a rapid analytical approach for the simultaneous determination of Cr(VI) and Cr(III) in environmental waters by hydrophilic interaction chromatography (HILIC) coupled with ICPMS under a water-rich condition. 2,6-Pyridinedicarboxylic acid (PDCA) was used to unify Cr(III) species in various chemical forms into a stable Cr(III)-PDCA anion complex and then separated from Cr(VI) oxyanion on a diol-bonded polymer-based HILIC column. An aqueous mobile phase containing 50mmol L-1 ammonium acetate (pH 7.0), 2mmol L-1 PDCA, and 4% acetonitrile successfully separates chromium species as well as chloride ions. In addition, our method elutes Cr(VI) preferentially over Cr(III)-PDCA, enabling rapid determination of Cr(VI), and both chromium species were analyzed within 6.2min. The detection limits of 0.19μg L-1 for Cr(VI) and 0.35μg L-1 for Cr(III) at m/z 52 under He collision mode are comparable to or better than the conventional ion exchange chromatography-ICPMS methods, and quantitative recovery was obtained from spike-recovery tests on river water samples containing various levels of matrix. Optimization experiments of the HPLC conditions indicate that the retentions of Cr(VI) and Cr(III)-PDCA are characterized by electrostatic and nonpolar interactions, respectively. The retention behavior of inorganic anions and cations in water-rich conditions observed in this study will provide new insights into the separation mechanism in polymer-based HILIC columns, which has been poorly understood.

A performance comparison of photo-fenton decolorization of methylene blue by using bentonite/iron composites prepared by liquid phase and solid phase ion exchange method

Nowadays, there is a wide range of pollutants present, which requires the treatment of wastewater. The photo-Fenton method has been recognized as valuable in this area. In this study, iron/bentonite composites were created using both liquid phase and solid phase iron exchange techniques, and they were utilized as a photocatalyst for the degradation of methylene blue through photo-Fenton process. Various factors affecting the photocatalytic decolorization were investigated, including the initial concentration of the dye, weight of the catalyst, pH of the solution, and concentration of hydrogen peroxide. The decolorization efficiency of the iron/bentonite composites prepared using the solid phase and liquid phase ion exchange approaches was found to be 99% and 95%, respectively. Based on the data, it can be concluded that the performance of both catalysts was almost equally influenced by the initial dye concentration, catalyst weight, solution pH, and hydrogen peroxide concentration. Moreover, the solid phase ion exchange method demonstrated greater reusability compared to the liquid phase ion exchange method. Consequently, it can be stated that the solid phase ion exchange approach is a suitable and straightforward alternative to the conventional liquid phase ion exchange method for producing a photo-Fenton catalyst.

Isolation of arabinose and galactose from industrial sidestreams in high yield and purity

Monosaccharides such as L-arabinose (Ara) and D-tagatose (derived from D-galactose, Gal) are low-calorie sweeteners associated with improved glycaemic and insulin control compared to disaccharides such as sucrose. However, alternative sources and better sugar-sugar separation methods are needed to improve the sustainability and economics of their production. Here, these sugars were obtained from purified and ultrafiltered compression screw pressate (CSP) of thermo-mechanical pulping of softwood (Pinus radiata) and orange peels (OPs). Ba-substituted zeolite X (BaX) molecular sieves showed superior separation performance of Ara from other sugars compared to conventional Ca-form ion exchange resin. To facilitate subsequent separation of sugars, OP hydrolysates were fermented to leave just Ara and Gal, while OP pectin was hydrolysed to generate a Gal-rich mixture. Overall, BaX has good potential for separating Ara from Ara-rich hydrolysates containing several different sugars. It is also suited for separating Ara and another monosaccharide such as Gal or Xyl in the absence of other sugars.

Two-dimensional graphene oxide/MXene lamellar membrane cross-linked by urea with adjustable interlayer spacing for efficient dye rejection and ion sieving

Two-dimensional (2D) membranes demonstrate good performance in molecular and ion separation due to their unique layer structure. However, the sieving performance of 2D membranes is severely limited by drawbacks such as poor stability and low mass transfer rates. Here, we propose a design strategy using urea as a cross-linking agent to construct stable and regular nanochannels inside the graphene oxide/MXene (GO/MXene) composite membranes. More importantly, by changing the composition, the effective interlayer spacing of the membrane can be easily adjusted within 4.47–8.92 Å with angstrom-level precision for tunable ion sieving. The composite membrane exhibits high water permeance (79.58 L m−2 h−1 bar−1) and excellent small molecule dye rejection (>99 %). Moreover, depending on the ionic valence state, the membrane exhibits significant ion sieving. The good Cl−/SO42− selectivity (11.64) makes it a promising alternative to conventional ion exchange membranes. This study demonstrates an innovative and facile way to construct 2D lamellar membranes with stable structures for efficient and precise separation.

Layered metal sulfides with MaSbc- framework (M = Sb, In, Sn) as ion exchangers for the removal of Cs(Ⅰ) and Sr(Ⅱ) from radioactive effluents: a review.

Nuclear power has emerged as a pivotal contributor to the global electricity supply owing to its high efficiency and low-carbon characteristics. However, the rapid expansion of the nuclear industry has resulted in the production of a significant amount of hazardous effluents that contain various radionuclides, such as 137Cs and 90Sr. Effectively removing 137Cs and 90Sr from radioactive effluents prior to discharge is a critical challenge. Layered metal sulfides exhibit significant potential as ion exchangers for the efficient uptake of Cs+ and Sr2+ from aqueous solutions owing to their open and exchangeable frameworks and the distinctive properties of their soft S2- ligands. This review provides a detailed account of layered metal sulfides with MaSb c- frameworks (M = Sb, In, Sn), including their synthesis methods, structural characteristics, and Cs+ and Sr2+ removal efficiencies. Furthermore, we highlight the advantages of layered metal sulfides, such as their relatively high ion exchange capacities, broad active pH ranges, and structural stability against acid and radiation, through a comparative evaluation with other conventional ion exchangers. Finally, we discuss the challenges regarding the practical application of layered metal sulfides in radionuclide scavenging.

Economical-effective purification of brackish water through an integrated capacitive desalination & boron adsorption system

The escalating scarcity of high-quality water for potable, industrial, and agricultural use necessitates innovative methods to augment freshwater supply from unconventional sources. This study primarily aims to lower boron (B) and chloride (Cl−) levels in brackish water to meet water quality standards of B < 0.5 mg/L and Cl− < 250 mg/L. To meet this goal, an innovative adsorbent, OQAS-AC@NGO, was used for boron removal. It combines organosilicon quaternary ammonium chloride (OQAS) modified activated carbon (AC) within a self-assembled nitrogen-doped graphene oxide (NGO) structure. Before boron removal, a capacitive deionization (CDI) system was used, employing OQAS-AC as the anode and COOH-modified AC as the cathode for chloride ion electrosorption. Through this cooperation procedure, the treated water meets the required quality standards while significantly reducing chemical costs by approximately 13.5 times when compared to conventional ion exchange resin methods for adsorbent regeneration. Moreover, the OQAS-AC@NGO adsorbent sustains its efficiency through multiple cycles, outperforming non-assembled N-GO in terms of yield, performance, and water flux. This underscores the cost-effective adsorbent preparation and enhanced water productivity. Economic analysis endorses the integrated CDI & B adsorption approach, advancing both sustainable water treatment processes and practical industrial applications.

Enhancing quantum efficiency of Mn4+-doped fluoride phosphors through reverse doping strategy toward potential biological detection

Mn4+-doped fluoride red-emitting materials are renowned for their distinct characteristics, including fixed emission peaks and narrow spectral emission, rendering them highly favored in photoluminescent light-emitting diodes (LEDs). However, achieving ultra-high-concentration Mn4+ doping in fluoride phosphors is imperative to enhance quantum efficiency. Nevertheless, attaining such doping levels in metastable compound systems poses considerable challenges. In this study, we introduce an innovative reverse doping strategy, leading to the synthesis of Mn4+-doped cubic K2SiF6 phosphor (11.38 mol %) from hexagonal K2MnF6. Remarkably, this approach significantly improves the external quantum efficiency (EQE) to 66.7 % upon 450 nm excitation. Through systematic comparisons with conventional co-precipitation and ion exchange methods, our findings unequivocally demonstrate the superior efficacy of this approach in achieving high-concentration Mn4+ ion doping within relatively insoluble matrices. The successful application of our optimized phosphor enabled the fabrication of a red light-emitting diode (LED) that exhibits an exceptional photoelectric efficiency of 31.67 % at 350 mA, surpassing the performance of a commercial red LED chip. Furthermore, the stable red-light emission from the phosphor-converted LED (pc-LED) proves instrumental in rapid-response vascular imaging, showcasing the potential of our findings in advancing light sources for biological detection applications. This research provides valuable insights into enhancing red emission efficiency in slightly-soluble fluoride phosphors via novel synthetic strategy, unlocking possibilities for the development of highly efficient light sources in biological detection and imaging applications.

Effects of Cold Sintering on the Performance of Zeolite 13X as a Consolidated Adsorbent for Cesium.

Cold sintering, a novel low-temperature consolidation technique, has shown promising results in various inorganic materials. However, the application of this technique to nanoporous materials for energy and environmental fields is not yet fully understood. This study investigates the effects of cold sintering on the relative densities, compressive strengths, chemical durabilities, crystal structures, specific surface areas, and adsorption capacities of zeolites. Cold sintering at 200 °C achieved 10 to 20% greater densification than conventional high temperature (700 °C) sintering; however, the original nanoporous structure of dry cold sintered zeolite was not maintained. Introducing liquid agents during the cold sintering process resulted in reduced degradation of the SSA and increased densification. Using NaOH as the liquid agent increased the solubility of elements in zeolite, which promoted chemical mobility and achieved the highest relative density (96.7 ± 2.8%). However, soluble layers between the particles led to fragmentation, making it unsuitable for aqueous applications. Using H2O as the liquid agent resulted in a relative density of 90.4 ± 4.1% while maintaining the nanoporous properties and structural integrity of zeolite under water. The cesium adsorption capacity (19.0 ± 0.1 mg·g-1) was similar to that of conventional zeolite ion exchangers, indicating that cold sintering with H2O was an efficient, economical, and safer alternative to conventional high-temperature consolidation method. Our findings suggest that this cold sintering can be applied to other nanoporous materials, such as metal-organic frameworks and covalent organic frameworks, in separation, catalysis, and adsorption applications.

Electrical Manipulation of Orbital Current Via Oxygen Migration in Ni81 fe19 /Cuox /Tan Heterostructure.

The orbital Hall effect and the interfacial Rashba effect provide new approaches to generate orbital current and spin-orbit torque (SOT) efficiently without the use of heavy metals. However, achieving efficient dynamic control of orbital current and SOT in light metal oxides has proven challenging. In this study, we demonstrate that a sizable magnetoresistance effect related to orbital current and SOT can be observed in Ni81 Fe19 /CuOx /TaN heterostructures with various CuOx oxidisation concentrations. The ionic liquid gating induces migration of oxygen ions, which modulates the oxygen concentration at the Ni81 Fe19 /CuOx interface, leading to reversible manipulation of the magnetoresistance effect and SOT. The existence of a thick TaN capping layer allows for sophisticated internal oxygen ion reconstruction in the CuOx layer, rather than conventional external ion exchange. These results provide a method for the reversible and dynamic manipulation of the orbital current and SOT generation efficiency, thereby advancing the development of spin-orbitronics devices through ionic engineering. This article is protected by copyright. All rights reserved.

Deduction of carbon footprint for membrane desalination processes towards carbon neutrality: A case study on electrodeionization for ultrapure water preparation

Decarbonization of the industrial sector, especially in power generation, is vital for achieving carbon neutrality. The life-cycle greenhouse gas (GHG) emissions, namely carbon footprint, of a technology under the decarbonizing macro-environment should be deduced to reveal further opportunities for GHG reduction. Herein, a case study on ultrapure water (UPW) preparation by electrodeionization (EDI) was investigated through life cycle assessment (LCA) and compared with a conventional mixed-bed ion exchange (MBIX) technology. The carbon footprint of the EDI process was quantified as 1.30 kg CO2-eq/metric ton UPW, which is 27.73 % lower than the MBIX. With a decarbonized power grid and recycling of wasted EDI modules, the carbon footprint will be reduced by 91 %. Meanwhile, the proportion of module production and waste management will increase to 18 %. Thus, we suggest reducing the process energy consumption and improving the current efficiency of the EDI process by process modeling and optimization. With the decarbonization of electricity, the degraded reuse of plastic and the recycling of ion-exchange membranes and resins could be considered. The application of LCA to quantify the carbon footprint and provide suggestions for low-carbon designs could be extended to membrane desalination or industrial processes, supporting the revolution towards carbon neutrality.

High Li-Ion Selectivity of Five-Coordinate Layered Titanate K2Ti2O5.

Selectivity of ion exchangers is an important topic in adsorption science owing to its specific application in resource recovery and environmental remediation. In this study, the cation exchange property of the submillimeter-sized five-coordinate K2Ti2O5 (KTO) crystals is demonstrated. Adsorption isotherm measurements were performed on KTO crystals ion-exchanged with alkali metal cations including Li+, Na+, Rb+, and Cs+. The maximum adsorption amounts of Li+, Na+, Rb+, and Cs+ on KTO were 2.70, 1.15, 0.59, and 0.42 mmol g-1, respectively, which is contradictory to the "normal" selectivity sequence (Cs+ > Rb+ > K+ > Na+ > Li+) of conventional ion exchangers, including clays and organic resins. The Kielland plots for the Li+ and Cs+ exchange experiments showed preferential Li+ adsorption on KTO, which supports the high Li+ selectivity. The interlayer distance for M+-exchanged KTO (M = Li, Na, Rb, and Cs) was dependent on cation type. Raman and X-ray absorption near-edge structure spectroscopic analyses of the KTO samples indicated that certain Ti species in KTO underwent hydrolysis, and thereby formed hydroxyl groups on the KTO surface during ion exchange. The origin of the high Li+ selectivity of KTO is discussed herein based on experimental characterization results.

Electrochemically embedded nickel oxide in a highly porous manganese oxide film with enhanced catalytic kinetics of the urea oxidation reaction

The use of well-dispersed nickel catalysts with atomic-scale sizes is an effective approach for maximizing catalytic activity and selectivity for the urea oxidation reaction (UOR). Herein, a porous ultrathin film of Birnessite-type manganese oxide is anodically deposited on a nickel substrate as a catalyst support. Some of the intercalated sodium ions are replaced by the dissolved nickel ions from the nickel substrate in the anodic process, forming manganese oxide with partially intercalated nickel ions (denoted MnO2). The amount of nickel species can be easily increased by cyclic voltammetry in the nickel sulfate electrolyte (denoted MnO2-Ni), without the relatively time-consuming process of conventional ion exchange. Most of the embedded nickel species are catalytic Ni3+ ions, rendering MnO2-Ni a favorable catalyst to boost the UOR. The cyclic voltammetry results reveal that Ni3+ catalysts, when inserted into the layer-structured manganese oxide, can increase the electroactive surface area for the adsorption of urea and increase the charge-transfer rate constant for the Ni3+/Ni2+ redox couple, leading to an improved catalytic rate constant of the UOR. A highly porous manganese oxide matrix provides many transport pathways for facilitating UOR kinetics. Electrochemical impedance spectroscopy shows that MnO2-Ni has lower direct and indirect UOR impedances than MnO2 and bare Ni electrodes, leading to a greater oxidation current and lower onset potential.

Cu, Co, or Ni species in exchanged Y zeolite catalysts and their denitration performance for selective catalytic reduction by ammonia

Identifying the role of Cu, Co, or Ni species in exchanged zeolite catalysts by different preparation methods has been widely concerned for selective catalytic reduction by ammonia (NH3-SCR). Here, we found that ammonia wet ion exchange method (AWIE) was useful for increasing ionic species and improving ion polymerization degree in traditional NaY (Si/Al = 2.5) zeolites. Cu, Co, and Ni substituted Y zeolite prepared by AWIE method achieved better SCR performance than those by conventional wet ion exchange method (CWIE). Meanwhile, the coordination states and chemical environments of Cu, Co, and Ni exchanged species influenced the redox and adsorption properties of catalysts. Cu-NH3-IE catalyst had a wider SCR temperature window than Co-NH3-IE and Ni-NH3-IE catalysts owing to its more stable NH3 adsorption, lower temperature, and smaller area of reduction peak. We proposed that the balance of NH3 adsorption and oxidation in thermodynamics and kinetics was the key for high N2 selectivity. This work provided a new idea for modifying the active sites of zeolite catalysts to achieve high activity and N2 selectivity in a broad temperature window.

Detailed investigation of effective trace Cr(VI) removal mechanism by anion exchange resin with phenol–formaldehyde matrix

Prolonged exposure to trace Cr(VI) concentrations in potable water can cause serious health problems in living beings. A weak base anion exchange resin, Duolite A7, showed a large capacity for trace Cr(VI) removal from a background of competing anions present at much higher concentrations, while conventional ion exchangers and adsorbents become ineffective due to lack of selectivity under similar conditions. The objective of this study was to find out the mechanism behind such significant capacity shown by the resin. Fixed-bed column studies showed that the resin was fully exhausted below 4,000 bed volumes (BVs) for pH 7, whereas no breakthrough was observed for 25,000 and 131,000 BVs at pH 5 and 3, respectively. Extensive characterization studies revealed that redox reactions were also occurring inside the resin in addition to ion exchange, where Cr(VI) oxidized the amine functional groups and phenol–formaldehyde matrix while itself getting reduced to Cr(III). Cr(III) formed was either precipitated inside the resin as Cr(OH)3 or bound with the oxidation products such as carboxylic acid groups. Analysis of treated water showed that formaldehyde, a carcinogen, was formed due to oxidative attack of Cr(VI) on the resin and was released in the effluent at trace concentrations. A detailed understanding of the mechanism would motivate the development of such redox-active sorbents for selective trace Cr(VI) removal from contaminated drinking water.

(Invited) Next Generation Ion Exchange Membranes for Electrochemical Polymer Membrane Processes

The ion exchange membrane is a key component in many electrochemical membrane processes such as fuel cells, flow batteries and electrolysers. Typically, these ion exchange membranes are assembled in stacks and allow the transport of the charge carrying component, i.e. a cation (e.g. proton) or an anion, while retaining the other species and electrolytes preventing their crossover to the other side of the cell. Simultaneously electrons travel through an external circuit powering a device or to store energy.Conventional ion exchange membranes have two major problems: They are based on expensive materials (e.g. Nafion®e. PFSA; perfluorosulfonic acid) or on environmentally harmful chemicals and chemical reactions. Although due to its molecular structure and composition, PFSA membranes show good performances, the major limitation of PFSA membranes is the very high material costs often contributing for more than 35% to the total stack costs [1, 2].One of the major challenges of ion exchange membrane development is the tradeoff between high ion transport rates through the membrane while simultaneously preventing electrolyte crossover [3]. This talk will first present a comprehensive overview of required membrane characteristics and an extensive benchmark study of state-of-the-art performances of ion exchange membranes in different electro-membrane processes. Following on this, the challenges in ion exchange membrane development will be addressed and most importantly two new routes for the development of next generation ion exchange membranes will be presented and their characteristics will be compared to those of a series of extensively benchmarked commercially available ion exchange membranes.The first approach, electrospinning is an effective, versatile method to produce cheap ion exchange membranes [3-6]: Multiple polymers can be employed simultaneously during spinning and this is combined with high degrees of interchain entanglement. This results in an interconnected network of ionic pathways that promote high ionic conductivities confined in a matrix of an inert polymer that guarantees high rejections towards electrolytes to prevent crossover (Figure 1a). Moreover, it is a simple technique that can be easily adapted to large scale production.The second approach uses liquid crystalline (LC) polymers to make ion exchange membranes [7]. This approach has the potential to offer true molecular selectivity and a high degree of flexibility to actually tune this selectivity. LC polymer materials self-organize into structures with well defined isoporosity (Figure 1b). Subsequent template removal or chemical bond cleavage with an acid or base results in the formation of molecular pores. The pores of these materials can be functionalized and depending on the functionality, selectivity can be introduced. Depending on the bulkiness of the functional group also pore sizes can be smaller or bigger. Crosslinking of the formed structures allows control over the swelling of the material and with that reduces crossover. In this way one can rely on both charge-charge interactions as well on size sieving to separate species. The major challenge is the formation of organized structures over larger length scales and the identification of structure-property relationships and with that control over the membrane separation performance.Design principles of both newly developed membrane types are discussed, the membranes are extensively characterized and their performance in electrochemical processes is compared to that of conventional ion exchange membranes. The talk is concluded with a future outlook on the perspectives of ion exchanhe membrane development. T. Cho, et al., Energy Technol. 1 (2013) 596–608. https://doi.org/10.1002/ente.201300108.Lin, et al., J. Electrochem. Soc. 163 (2016) A5049–A5056. https://doi.org/10.1149/2.0071601jes.A. Hugo, et al., Journal of Membrane Science 566 (2018) 406. 10.1016/j.memsci.2018.09.006.Woo Park, et al., J. Membr. Sci. 541 (2017) 85–92. https://doi.org/10.1016/j.memsci.2017.06.086.Choi, et al., Macromolecules. 41 (2008) 4569–4572. https://doi.org/10.1021/ma800551w.J.B. Ballengee, P.N. Pintauro, Macromolecules. 44 (2011) 7307–7314. https://doi.org/10.1021/ma201684j.Kloos, et al., Journal of Membrane Science 620 (2021) 118849. https://doi.org/10.1016/j.memsci.2020.118849 Figure 1

Facile Synthesis of Novel Polyethyleneimine Functionalized Polymeric Protic Ionic Liquids (PolyE‐ILs) with Protagonist Properties for Acid Catalysis

AbstractPolyethyleneimine (PEI), a potent architecture backbone was explored for the synthesis of novel polymeric ionic liquids (PolyE‐ILs) with protagonist properties. The simple quaternization of PEI dendrimer with Bronsted acids (H2SO4, H3PO4, CH3SO3H, CF3COOH and TsOH) leads to formation of series of protic PolyE‐ILs with corresponding counter anions [HSO4]−, [H2PO4]−, [CH3SO3]−, [CF3COO]− and [TsO]−. The physicochemical properties of synthesized PolyE‐ILs were studied by using TGA, Hammett acidity, hydrodynamic radii, solubility, and elemental analysis. PolyE‐ILs showed characteristic Hammett acidity (0.94–1.78), good thermal stability (&lt;250 °C) and enhanced hydrodynamic radii. However, use of PolyE‐IL can be promoted for their wide applications as an acid catalysts. The reported PolyE‐IL‐1 with sulfonic acid counter ion was explored as catalyst for esterification of (E)‐cinnamic acids and it showed good catalytic activity. The enhanced hydrodynamic radii due to the branched architecture of PEI dendrimers facilities the separation process via Nanofiltration (NF) membrane with no membrane fouling. Thus, PolyE‐ILs can be highly active, easily recoverable, and reusable catalyst for esterification reactions with superior sustainability and economics. In addition to this the present one pot PolyE‐IL synthesis process is non‐complex and simple as compared to conventional post polymerization, ion exchange, and nucleophilic addition etc., strategies for synthesis of PILs.

Experimental and Theoretical Studies of Sonically Prepared Cu–Y, Cu–USY and Cu–ZSM-5 Catalysts for SCR deNOx

The objective of our study was to prepare Y-, USY- and ZSM-5-based catalysts by hydrothermal synthesis, followed by copper active-phase deposition by either conventional ion-exchange or ultrasonic irradiation. The resulting materials were characterized by XRD, BET, SEM, TEM, Raman, UV-Vis, monitoring ammonia and nitrogen oxide sorption by FT-IR and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). XRD data confirmed the purity and structure of the Y/USY or ZSM-5 zeolites. The nitrogen and ammonia sorption results indicated that the materials were highly porous and acidic. The metallic active phase was found in the form of cations in ion-exchanged zeolites and in the form of nanoparticle metal oxides in sonochemically prepared catalysts. The latter showed full activity and high stability in the SCR deNOx reaction. The faujasite-based catalysts were fully active at 200–400 °C, whereas the ZSM-5-based catalysts reached 100% activity at 400–500 °C. Our in situ DRIFTS experiments revealed that Cu–O(NO) and Cu–NH3 were intermediates, also indicating the role of Brønsted sites in the formation of NH4NO3. Furthermore, the results from our experimental in situ spectroscopic studies were compared with DFT models. Overall, our findings suggest two possible mechanisms for the deNOx reaction, depending on the method of catalyst preparation (i.e., conventional ion-exchange vs. ultrasonic irradiation).

Effect of polymer matrices of gels bearing a sulfo group on their catalytic properties for acetalization of glycerol to solketal and esterification of oleic acid to ethyl oleate

A novel type of copolymer gel bearing the sulfo group was developed as a heterogeneous acid catalyst for the solvent free acetalization of glycerol with acetone to form a desirable solketal, as well as the solvent free esterification of oleic acid with ethanol to form ethyl oleate as a biodiesel fuel. The copolymer gels were synthesized by the copolymerization of a primary monomer (ethoxy diethyleneglycol acrylate (EDGA), N-isopropylacrylamide (NIPA), etc.) with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). The copolymer gels, such as EDGA-co-AMPS gel and NIPA-co-AMPS gel, successfully catalyzed both reactions with a higher reaction rate than those of AMPS gel and the conventional sulfonic ion exchange resin (Amberlyst). According to Le Chatelier's principle, if a gel catalyst absorbs reactants well, and expels or poorly absorbs products, the apparent rate of the reaction occurring within the gel is enhanced. This hypothesis was examined by analyzing the solution absorptions of these gels and their reaction rates, including Eley–Rideal kinetic analysis.

Conventional and electric field-assisted ion exchange on glass-ceramics for dental applications

Ion exchange can be used to mechanically reinforce dental glass-ceramics to reduce the problems associated to the flaws created upon various processing steps and handling. This work introduces a novel ion exchange method to the field of dental glass-ceramic to increase the possibilities of preparing highly reliable glass-ceramic restorations. The aim of the study was to compare Electric Field-Assisted Ion Exchange with conventional method, for newly developed nepheline based dental glass-ceramic. Multicomponent glass system was synthesized using melt-quench method and then prepared into glass-ceramic specimens via powder sinter-crystallisation route. The prepared glass-ceramic specimens were tested for bi-axial flexural strength before and after ion exchange according to the dental ceramics ISO 6872:2015. Ion exchange process was carried out in molten potassium nitride and the potassium penetration depth determined by EDXS was found greater and occurring in a matter of minutes within the nepheline crystal structure during electrical field assisted ion exchange compared with several hours of conventional treatment. The newly developed nepheline glass-ceramic system and the results achieved by electrical field assisted ion exchange may renew the ion exchange concept for dental application.