Conventional Ion-exchange Method Research Articles

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.

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.

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.

Promotion of the performance of Cu-SSZ-13 for selective catalytic reduction of NOx by ammonia in the presence of SO2 during high temperature hydrothermal aging

The influence of SO2 presence during high temperature hydrothermal aging (600, 700, and 800 °C) on the performance of Cu-SSZ-13 prepared by the conventional ion-exchange method for selective catalytic reduction of NOx by NH3 (NH3-SCR) was studied. The high-temperature activity of Cu-SSZ-13 is obviously enhanced by the SO2 presence for the 700 and 800 °C-aged samples and is not hampered for the 600 °C-aged sample. The presence of SO2 during hydrothermal aging has no influence on the framework Al. The interaction of Cu2+ with SO2 results in the formation of ZCuHSO4, which helps suppress the aggregation of Cu2+ into CuO and maintain more isolated Cu2+, leading to higher activity at high temperatures. The low Cu content yields higher relative population of Cu2+ species at more stable sites. The low-temperature (≤350 °C) activity is slightly lowered for the 600 and 700 °C-aged samples.

Kinetic evaluation of dehydration in MxNa96-xLSX (M= Li+, Ca2+ and Ag+) zeolites and resulting effects on selective adsorption of N2 and O2

Abstract The purpose of this study is to evaluate the dehydration kinetics of MxNa96-x-LSX (M = Li+, Ca2+ and Ag+) zeolites and assess their potential for N2/O2 adsorption and selectivity using ideal adsorbed solution theory. In order to achieve our objective, MxNa96-x-LSX (M = Li+, Ca2+, and Ag+) zeolites were prepared via conventional ion exchange methods from Na-LSX zeolite. Meanwhile, their structural and textural properties were characterized by N2 adsorption-desorption, TG-DTG, ICP-OES, XRD, FT-IR, EDS, elemental mapping and SEM techniques. The kinetics (activation energy, pre-exponential factor, and most probable mechanism/model) of dehydration process were investigated via Kissinger, Flynn-Wall-Ozawa and Coats-Redfern methods. The results show a strong dependence on the choice of mechanism function, which can help in proposing the best relevant kinetic model. Moreover, the results further reveal that Li+ and Ca2+ ions (which are inexpensive) in Li-LSX and Ca-LSX fill the low-energy sites SI, SI′, SII, and SII′ first and then SIII and SIII′ sites. Li-LSX and Ca-LSX hold comparative advantages, which suggest that they would be the most promising adsorbents for air separation and pure oxygen production by pressure swing adsorption. However, Ag-LSX presents superior performance at relatively low pressures. Therefore, the quantitative evaluation of kinetic parameters of dehydration is necessary to provide the theoretical principles in understanding N2 and O2 adsorption phenomena.

Surfactant-assisted synthesis of direct Z-scheme AgBr/β-Ag2WO4 heterostructures with enhanced visible-light-driven photocatalytic activities

Compared with the conventional two-step ion exchange method used for the fabrication of AgBr/β-Ag2WO4 heterostructures, herein, a series of AgBr/β-Ag2WO4 direct Z-scheme heterostructures were efficiently fabricated via a simple surfactant-assisted one-step precipitation strategy. The phase structure, morphology, chemical composition as well as photocatalytic mechanism of the as-obtained AgBr/β-Ag2WO4 heterostructures were systematically characterized by using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Ultraviolet–Visible diffuse reflectance spectra (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), Photoluminescence spectrum (PL), photoelectrochemical tests. Photocatalytic degradation of Rhodamine (RhB) under visible light was carried out as a probe to assess its photocatalytic activity. The result indicates that AgBr/β-Ag2WO4-30% exhibits the highest photocatalytic activity, which is approximately 1.7 and 135.9 times as high as that of pure AgBr and pure β-Ag2WO4, respectively. The pathway of charge carriers separation and transfer in the AgBr/β-Ag2WO4 heterostructures and the direct Z-scheme mechanism were depicted in details based on the systematic characterizations and measurements. The enhancement of the photocatalytic performances of the as-prepared AgBr/β-Ag2WO4 heterostructures are mainly attributed to the larger specific surface area and Z-scheme system formed between these two semiconductors, leading to the spatial separation of the photoinduced electron and hole. This work may provide a new sight to understand the mechanism of AgBr/β-Ag2WO4 heterostructures, which is direct Z-scheme heterojunctions rather than type-II heterojunctions.

Surface modification of montmorillonite by the use of organic cations via conventional ion exchange method

The main problems in synthesis polymer clay nanocomposites (PCNs) with nanoclay filler is the nanoclay was not compatible to most of polymer matrix due to its hydrophilicity which is often causes agglomeration of the nanoclay in the polymer matrix. Surface modification of nanoclay for a good compatibility with polymer matrix is the most important step to achieve homogenous dispersion of clay platelets in polymers. Modification of nanoclay montmorillonite (MMT) can be done through conventional ion exchange method using cationic surfactants. Montmorillonite (MMT) was modified with several cationic surfactants based on its cationic exchange capacity (CEC). The effect of chemical composition of modified MMT on the basal spacing were evaluated by small angle x-ray diffraction (SAXS), the highest basal spacing expanded from 1.21 nm to 2.00 nm showed the intercalation of the surfactant ion into the intergalerry of sodium montmorillonite clay layers which caused increasing of surface area and porosity. FTIR spectra shows the successful of inserting alkyl groups from cationic surfactant in interlayer space of montmorillonite. Organophilization reduces the energy of sodium montmorillonite and improves its compatibility with organic polymer. Dispersion analysis and contact angle results shown the surface wettability of montmorillonite was enhanced from hydrophilic to organophilic and resulting good solubility in monomer phase.

The electrochemical properties of V-doped Li2Ti6O13 and Na2Ti6O13 anode materials

Li2Ti6−xVxO13 and Na2Ti6−xVxO13 (where x = 0, 0.025, 0.05, 0.1) are prepared by conventional ion exchange method and solid-state reaction technique, respectively. According to XRD analysis, increasing V contents in the structures cause the formation of LiVO3 and LiV3O8 phases for x ≥ 0.025 substitutions for Li2Ti6O13 and Na4V2O7 in structure for Na2Ti6O13 x ≥ 0.025. It was observed two redox peaks for both undoped compositions which are related to insertion and deinsertion of Li/Na ions in the structure. The battery performances were investigated for Li2Ti6−xVxO13 and Na2Ti6−xVxO13 systems and it is found that pure Li2Ti6O13 sample has showed the capacity of 36 mAh g−1 and 27 mAh g−1 for 1 and 1000 cycle respectively which show better capacity fade when compared with the other anode materials. The battery performance of undoped Na2Ti6O13 sample has 40 mAh g−1 and 34 mAh g−1 for 1 and 1000 cycle respectively. In addition to this, the x = 0.05 V-substitution has showed 66 mAh g−1 for the first cycle which is higher than that of the undoped sample. It was investigated the structural deformation of the cells by in situ XRD during to CV process and ex situ XRD and Raman techniques after cycling of the cells. It is predicted that the changes of the reflection planes of the crystallites/grains during to cycling of the cells may be the main reason of the decrease of the battery performance which is related to insertion and de-insertion energy of the Li-ions.

Monoclinic-celsian ceramics formation: Through thermal treatment of ion-exchanged 3D printing geopolymer precursor

Based on conventional ion exchange method from zeolite materials, we herein report a facile synthetic procedure to prepare monoclinic celsian ceramics through thermal treatment of ion-exchanged 3D printing geopolymer precursors. In this contribution, both ion exchange process and thermal evolution of celsian precursors were systematically investigated. The results proved 3D printing Na- and K- based geopolymer were ideal precursors with low residual Na+ content (0.10 meq/g) and K+ content (0.05 meq/g) and translated into monoclinic celsian after being heated at 1400 °C. With increasing Sr2+ doping concentration from 20% (mole ratio) to 30% (mole ratio), more significant phase transition results (hexagonal → monoclinic) were observed. All 3D printing geopolymer precursors kept fine integrity and stable 3D structure upon ion exchange process and heating, indicating the combination of geopolymer technique and 3D printing opens up a versatile and robust way to yield monoclinic celsian ceramics and related components of complex shapes.

Interplay between Fe-Titanate Nanotube Fragmentation and Catalytic Decomposition of C2H4: Formation of C/TiO2 Hybrid Interfaces

This paper reports the synthesis of Fe-titanate nanotubes by means of the conventional ion-exchange method with iron nitrate solutions. As the iron-rich nanotubes were found to contain the catalyst precursor intrinsically dispersed in their structures, the unprecedented possibility of using this kind of materials for building carbon nanostructures, firmly attached at the surface of the forming TiO2 nanoparticles, was verified. The catalytic decomposition of ethylene, used as a carbon source, was performed at a relatively high temperature (750 °C) when the nanotubes undergo an irreversible phase transformation to form anatase and rutile nanoparticles. Due to the different amounts of Fe ions in the nanotubes, distinct types of carbon/TiO2 hybrid interfaces were formed, ranging from amorphous (lower Fe3+ concentration) to the more crystalline graphitic domains (higher Fe3+ concentrations), as documented by the microstructure of the treated samples. The present approach is of potential interest for (photo)catalytic and energy conversion/transport applications.

Recovery and Recycling of Tungsten by Alkaline Leaching of Scrap and Charged Amino Group Assisted Precipitation

Herein, we present a charged amino group assisted precipitation (CAAP) method for recovery and recycling of high-purity tungsten from a solution obtained by alkaline leaching of cemented carbide (WC–Co alloy) scrap. When lysine hydrochloride, which contains a charged amino group (NH3+), was added to an alkaline leaching solution containing tungsten (307 mmol L–1), sodium (1236 mmol L–1), and vanadium (1.7 mmol L–1), over 90% of the tungsten was rapidly recovered as a lysine–tungsten precipitate. The sodium in the precipitate was successfully removed by a simple washing process. Calcination was then performed to obtain 99.6% high-purity tungsten oxide, and reduction and carburization of the obtained tungsten oxide resulted in tungsten carbide. A pilot study using the CAAP method demonstrated a considerable decrease (60%) in the displacement (i.e., volume of chemicals used/waste created) compared with that required for the conventional ion-exchange method for tungsten recycling.

Microwave-Assisted Synthesis of Ethylene Glycol-Intercalated NiAl LDHs and Their Application for Intracrystalline Catalytic Esterification with Naphthenic Acids in Crude Oil

Ethylene glycol (EG)-intercalated layered double hydroxides (LDHs) with various Ni/Al molar ratios were prepared by a microwave-assisted ion exchange method. In comparison with the conventional ion exchange method, this method can achieve a more ordered layered structure and reduce the ion exchange time from 12 h to 30 min. The as-prepared EG-intercalated LDHs were used as esterification catalysts to remove naphthenic acids in crude oil. It is found that EG-intercalated LDHs may act as nanosized intracrystalline catalytic microreactors, attributed to the preintercalated EG which reduces the diffusion resistance, the enlarged interlayer space which facilitates the access of naphthenic acids, and metal catalytic sites in the layer. The confined interlayer space enhances the collision between reactants and accelerates the reaction. Therefore, EG-intercalated LDHs exhibit several times higher acid removal ratio and EG conversion than nitrate LDHs. The increasing Ni/Al ratio increases the amount of catalytic s...

Synthesis and characterization of Cu-MFI catalyst for the direct medium temperature range NO decomposition

Abstract In this study the physico-chemical and catalytic properties of copper bearing MFI zeolites (Cu-MFI) with different Si/Al and Si/Cu ratios were investigated. Two different methods for incorporation of metal ions into the zeolite framework were used: the ion exchange from the solution of copper acetate and the direct hydrothermal synthesis. Direct synthesis of a zeolite in the presence of copper-phosphate complexes was expected to generate more active copper species necessary for the desired reaction than the conventional ion exchange method. Direct decomposition of NO was used as a model reaction, because this reaction still offers a very attractive approach to NOX removal. The catalytic properties of zeolite samples were studied using techniques, such as XRD, SEM, EPR and nitrogen adsorption/desorption measurements at 77 K. Results of the kinetic investigation revealed that both methods are applicable for the preparation of the catalysts with active sites capable of catalyzing the NO decomposition. It was found out that Cu-MFI zeolites obtained through direct synthesis are promising catalysts for NO decomposition, especially at lower reaction temperatures. The efficiency of the catalysts prepared by both methods is compared and discussed.

Classical Keggin Intercalated into Layered Double Hydroxides: Facile Preparation and Catalytic Efficiency in Knoevenagel Condensation Reactions.

The family of polyoxometalate (POM) intercalated layered double hydroxide (LDH) composite materials has shown great promise for the design of functional materials with numerous applications. It is known that intercalation of the classical Keggin polyoxometalate (POM) of [PW12 O40 ](3-) (PW12 ) into layered double hydroxides (LDHs) is very unlikely to take place by conventional ion exchange methods due to spatial and geometrical restrictions. In this paper, such an intercalated compound of Mg0.73 Al0.22 (OH)2 [PW12 O40 ]0.04 ⋅0.98 H2 O (Mg3 Al-PW12 ) has been successfully obtained by applying a spontaneous flocculation method. The Mg3 Al-PW12 has been fully characterized by using a wide range of methods (XRD, SEM, TEM, XPS, EDX, XPS, FT-IR, NMR, BET). XRD patterns of Mg3 Al-PW12 exhibit no impurity phase usually observed next to the (003) diffraction peak. Subsequent application of the Mg3 Al-PW12 as catalyst in Knoevenagel condensation reactions of various aldehydes and ketones with Z-CH2 -Z' type substrates (ethyl cyanoacetate and malononitrile) at 60 °C in mixed solvents (V2-propanol :Vwater =2:1) demonstrated highly efficient catalytic activity. The synergistic effect between the acidic and basic sites of the Mg3 Al-PW12 composite proved to be crucial for the efficiency of the condensation reactions. Additionally, the Mg3 Al-PW12 -catalyzed Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate demonstrated the highest turnover number (TON) of 47 980 reported so far for this reaction.

Combined Experimental and Computational Approaches To Elucidate the Structures of Silver Clusters inside the ZSM-5 Cavity

A combination of experimental and computational analyses suggested the presence of Ag3 or Ag4 clusters inside a nanometer-sized cavity in Ag–ZSM-5 zeolites, which were formed from H–ZSM-5 using the conventional ion-exchange method in an aqueous silver nitrate solution. During the experimental analyses, we investigated the structural and absorption properties of Ag–ZSM-5 through UV–vis diffuse reflectance and X-ray absorption fine structure (XAFS) measurements. The results from the extended XAFS (EXAFS) analysis indicated that clusters contained in the ZSM-5 cavity have Ag–Ag separations of approximately 2.6 A. The UV–vis measurements indicated that the clusters located in the cavity present three prominent absorption bands centered at approximately 255, 287, and 331 nm for the sample treated at 473 K. The Ag–ZSM-5 treated at 573 or 673 K presents new UV–vis bands at approximately 303 and 319 nm. The experimental results regarding the structural and absorption properties of Ag–ZSM-5 could be well-reproduce...

Relations between iron sites and performance of Fe/HBEA catalysts prepared by two different methods for NH3-SCR

A series of Fe/HBEA catalysts was prepared by conventional impregnation (IMP) and liquid ion exchange (LIE) methods with various levels of iron contents, all of which was used to identify and quantify iron species and study the roles of different iron species in NOx conversion efficiencies, catalytic selectivity, and temperature dependencies. The composition and distribution of the iron species strongly depended on iron contents and preparation methods. LIE method preferred to produce more iron ions at ion exchange sites than IMP method, and then obtained highly active and selective Fe/HBEA catalysts. Isolated iron species at ion exchange sites was active in the NOx reduction with ammonia reaction (including N2O reduction with ammonia reaction), and iron oxide particles mainly contributed to the ammonia oxidation at the whole temperature range. The results of DRIFTS showed that nitrate species, Fe2+ mononitrosyls [Fe2+(NO)], and Fe2+ dinitrosyls [Fe2+(NO)2] were coadsorbed on the Fe/HBEA samples, yet the LIE samples preferred to yield much more nitrate and nitrosyl species than the IMP samples. Fe2+ mononitrosyls was found to be the key intermediates in the SCR reaction at 200°C, while the nitrates species, mainly generated on iron ion sites and adsorbed on zeolite support, did not take part in the SCR reaction. NH3-TPD and ammonia oxidation results showed zeolite acidity might not be critical for SCR reaction on Fe/HBEA catalysts, and would be inhibited with the introduction of iron.

Estimation of uranium isotope in urine samples using extraction chromatography resin

Introduction: Internal exposure monitoring for alpha emitting radionuclides is carried out by bioassay samples analysis. For occupational radiation workers who handle uranium in reprocessing or fuel fabrication facilities, there exist a possibility of internal exposure and urine assay is the preferred method for monitoring such exposure. Materials and Methods: Separation of Uranium is carried out by extraction chromatography using diamyl amyl phosphonate (U/TEVA) resin. This resin contains diamyl amyl phosphonate extractant supported on inert Amberlite XAD-7 (an acrylic ester) resin.The electrodeposited samples are counted using octet alpha spectrometery. Results and Discussion: The analysis time involved from sample loading to stripping is 2 h compared with the 3.5 h involved in conventional ion exchange method. The radiochemical yield was found in the range of 69-91%. Minimum detectable activity for uranium estimation for 3,60,000 s counting time at an average percentage recovery of 82 ΁ 8 works out to 0.21 mBq/d. Conclusion: The technique gives good and consistent radiochemical yield of 82% on repeated use of the chromatographic column when compared with ion exchange technique. Analysis time involved from sample loading to stripping using UTEVA is 2 h compared with the time involved of 3.5 h by the conventional ion exchange method.

Synthesis and Characterization of Fe/SUZ-4 Zeolite

The synthesized Fe/SUZ-4 zeolites using conventional ion exchange method. K/SUZ-4 zeolite was prepared with SiO2:Al2O3 molar ratio of 21.2 under hydrothermal process at 150°C for 4 days using tetraethylammonium hydroxide (TEAOH) as a template. Different amounts of Fe(II) were loaded in the synthesized K/SUZ-4 with different weight percentages:1, 3, 5, 8 and 10. Fe/SUZ-4 zeolite were investigated using atomic absorption spectroscopy (AAS), X-ray powder diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). The results show structures of Fe/SUZ-4 zeolites still have a narrow pore size distribution and needle-shaped crystal.

The effect of metal ions in MNaY-zeolites for the adsorptive removal of tetrahydrothiophene

The adsorptive removal of tetrahydrothiophene (THT) was carried out over transition metal ion-exchanged Na-Y zeolites. CuNa-Y, CoNa-Y, NiNa-Y and FeNa-Y were prepared by a conventional ion exchange method from Na-Y using the nitrate solutions of corresponding metals. N2 physisorption, inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and X-ray diffraction were conducted to characterize adsorbents. The temperature programmed desorption (TPD) of THT was also perfomed to probe the interaction between the adsorbent and the THT. The crystal structure of Y-zeolite was completely destroyed in FeNa-Y, which resulted in a insignificant amount of adsorbed THT. The breakthrough capacity, which is defined as the amount of sulfur adsorbed on the adsorbent before detecting sulfur species by PFPD, decreased in the following order CuNa-Y>CoNa-Y>NiNa-Y>>FeNa-Y. For interaction between THT and adsorbent, a TPD peak appeared over CoNa-Y at the highest temperature, which implies that the strongest interaction can be made between THT and Co2+ in CoNa-Y.

Simulation of SCR equipped vehicles using iron-zeolite catalysts

Iron-catalysts, based on ZSM-5 (FeZSM5) and Cuban natural Mordenite (FeMORD) zeolites have been prepared by a conventional ion-exchange method and their catalytic activity in the selective catalytic reduction (SCR) of NO with ammonia was studied in the presence of H 2O and SO 2. A commercial SCR catalyst (CATCO) based on V 2O 5–WO 3–TiO 2, was also studied as a reference. This paper presents the experimental results of using these catalysts without toxic vanadium and also exploits a neural network-based approach to predict NO x conversion efficiency of three SCR catalysts. The mathematical functions derived have been integrated into a numerical model to simulate diesel road vehicles equipped with SCR catalysts such as those studied here. The main results indicate that despite toxic vanadium and N 2O formation, CATCO shows better NO x conversion efficiencies. However, FeMORD does not produce N 2O and performs better than the FeZSM5. The simulation results on real cycles show lower level of NO x for heavy-duty and light-duty diesel vehicles compared with homologation load cycles.