Faujasite-type Zeolites Research Articles

Cu-Containing Faujasite-Type Zeolite as an Additive in Eco-Friendly Energetic Materials.

Regarding the current state of the art on the utilization of zeolites in industry, the application of zeolites as an additive to eco-friendly energetic materials indicates the innovative character of the present research. One of the most commonly used energetic materials in the mining industry (engineering works) is ANFO (ammonium nitrate fuel oil), due to its easy and cheap production procedure as well as its good energetic properties and vast possibilities for modification. In the present research, we investigated Cu-zeolite with a faujasite structure (Cu-FAU) as a modifier of ANFO-based energetic materials. Analysis of the results obtained from thermodynamic calculations of energetic performance led to the conclusion that the application of Cu-faujasite as an additive to ANFO resulted in a relevant reduction in the total emission of post-decomposition fumes, with simultaneous enhancement of the energetic properties of the energetic material, which corresponded with the changes in the status of the surface and the reduced thermal effect accompanying the ammonium nitrate's decomposition. From analysis of both the energetic performance and fumes, it may be concluded that our eco-friendly and enhanced energetic material can be used as a low-emission source of energy for the quarrying of raw materials.

Renewing Interest in Zeolites as Adsorbents for Capture of Cationic Dyes from Aqueous and Ethanolic Solutions: A Simulation-Based Insight into the Efficiency of Dye Adsorption in View of Wastewater Treatment and Valorization of Post-Sorption Materials.

The impact of solvents on the efficiency of cationic dye adsorption from a solution onto protonated Faujasite-type zeolite (FAU-Y) was investigated in the prospect of supporting potential applications in wastewater treatment or in the preparation of building blocks for optical devices. The adsorption isotherms were experimentally determined for methylene blue (MB) and auramine O (AO) from single-component solutions in water and in ethanol. The limiting dye uptake (saturation capacity) was evaluated for each adsorption system, and it decreased in the order of MB-water > AO-water > AO-ethanol > MB-ethanol. The mutual distances and orientations of the adsorbed dye species, and their interactions with the oxygen sites of the FAU-Y framework, with the solvent molecules, and among themselves were inferred from Monte Carlo simulations and subsequently utilized to rationalize the observed differences in the saturation capacity. The dye-solvent competition and the propensity of the dyes to form compact pi-stacked dimers were shown to play an important role in establishing a non-uniform distribution of the adsorbed species throughout the porous space. The two effects appeared particularly strong in the case of the MB-water system. The necessity of including solvent effects in modeling studies is emphasized.

Tuning the Hydrothermal Synthesis of FAU-type and ANA-type Zeolites Derived from the Philippine Bentonite

The synthesis of zeolites from local resources has been an attractive route to address the demand for more economical means in the production of zeolites for commercial applications. In particular, Philippine bentonite – a local clay material –has been used as a raw ingredient to synthesize zeolites, faujasite-type (FAU), and analcime-type (ANA) via hydrothermal synthesis. The silicon-aluminum ratio (SAR) and crystallization temperature were varied to investigate the conditions in the synthesis of pure FAU and ANA-type zeolites. X-ray diffraction allowed the identification of zeolite phases upon comparison to reference patterns from the International Zeolite Association database. The sample with the highest degree of crystallinity of 98% (ANA-type) was prepared at a temperature of 150 °C and an initial SAR of 1.18. This sample also exhibited the largest particle size of 29.1 μm in diameter. Scanning electron micrographs showed octahedral, spherical, and cross morphologies of the products, with average particle size ranging from 1.24 (± 0.13) to 29.1 (± 1.66) μm. The transformation of Philippine bentonite to different types of zeolites demonstrates the viability of local clays as raw resource material for hydrothermal synthesis of a wide range of zeolite frameworks.

Mechanical properties of low calcium alkali activated binder system under ambient curing conditions

These days, the construction industry is facing sustainability issues, leading to the selection of greener, low-carbon, alkali-activated materials. This study examines a low calcium alkali activated system composed of three constituents (ceramic brick, metakaolin waste, and phosphogypsum). The AAB compositions consist of the primary precursor, waste ceramic brick, which is increasingly (20–100 wt%) replaced with waste metakaolin. The alkaline solution was made of sodium hydroxide and water; dosage depended on the Na2O/Al2O3 ratio (1.00–1.36). The AAB specimens were inspected by using XRD (X-ray diffraction) and FT-IR (Fourier transform infrared spectroscopy) methods for the evaluation of mineral composition, accompanied by SEM–EDS (scanning electron microscopy & energy dispersive X-ray spectroscopy) for the analysis of the microstructure. The compressive strength after 7, 28 and 90 days, along with water absorption and softening coefficient were determined. Also, mixture calorimetry was established. The results have shown that the initial materials are suitable for producing medium-strength alkali-activated binder under ambient temperature. The maximum compressive strength was reached by using the combination of 80% CBW and 20% MKW (13.9 and 21.2 MPa after 28 and 90 days respectively). The compressive strength development was linked with the formation N–A–S–H gel and faujasite type zeolite. A higher level of geopolymerization in composition with metakaolin waste led to lower compressive strength. Consequently, binding materials with low demand of high final and especially early compressive strength could be produced under ambient temperature curing, making them more sustainable.

Additive-free synthesis of layer-like Faujasite-type zeolite X

Faujasite-type zeolite X (FAU-X) with a layered morphology was successfully synthesized by an additive-free route at a crystallization temperature of 90 °C for 24 h. The sample was dried at 70 °C for 40 h (designated FAU) and then calcined at 450 °C for 5 h (designated FAU-450). Both samples were analyzed by X-ray diffraction (XRD), which confirmed the formation of the FAU structure. In addition, from the XRD data and Energy Dispersive Spectroscopy, the Si/Al ratio was determined to be ~ 1.20, which is typical for FAU-X zeolite. Scanning Electron Microscopy revealed that both samples have morphologies corresponding to sheet agglomerate, with FAU-450 having an agglomerate size of 1.41 µm and a sheet thickness of about 0.13 µm. These values are close to the data obtained by transmission electron microscopy, where an agglomerate size of ~ 1.39 µm and a sheet thickness of ~ 0.12 µm were observed. From the Tauc’s plots for FAU and FAU-450, the values of direct and indirect band gaps were determined and found to be close for both samples. In the case of FAU-450, values of 4.35 eV and 3.12 eV were obtained for the direct and indirect transition, respectively. From the TGA/DTA data, it was found that FAU loses mass due to dehydration of the zeolite at temperatures below 350 °C, while the sample is structurally stable up to 700 °C.Graphical

1,2-dichlorobenzene gas-phase adsorption onto Nd3+ exchanged faujasite 13X beads - Influence of the exchange rate on adsorbed amounts and desorption temperatures

Aromatic chlorinated compounds, such as 1,2-dichlorobenzene, are considered as precursors of dioxin formation and their removal from flue gas using adsorption technology could be a solution. Faujasite type zeolites seem to be the most promising adsorbent, as the size of its porosity matches the size of the molecule. Even though the cationic faujasites are hydrophilic, the strength of interaction of chlorinated aromatic compounds adsorbed in porosity are higher than with more silicic faujasite such as FAU-NaY.FAU-NaX commercial beads have been Nd3+ exchanged at different rates. Dichlorobenzene dynamic gas adsorption has been performed via a thermobalance with vapours at concentration of 938 ppm in nitrogen gas flow and the quantities absorbed have been recorded during time. Then, from the coupling of a thermobalance with an in-line mass spectrometer, the desorbed quantities and desorption temperatures have been measured for both water and dichlorobenzene.Total quantities of 1,2-dichlorobenzene adsorbed onto partially exchanged FAU-Nd-NaX zeolites increases with the exchange rate: it has been measured a capacity of 23.3 wt % (relative to activated zeolite) for the most exchanged FAU-Nd-NaX at exchange rate of 53.6 %. For that zeolite, 74.7 % of the 1,2-dichlorobenzene is adsorbed at high-energy bonds with cations, desorbable at temperatures higher than 160 °C. The desorption temperature of dichlorobenzene decreases from 380 to 310 °C for FAU-NaX and the FAU-Nd-NaX at exchange rate of 53.6 % and remains higher than that of water. So that, thermal-desorption remains a separative process between water and chlorinated molecules previously adsorbed on cationic faujasites.

Adsorption of 5-fluorouracil, an anticancer drug, in faujasite-type zeolites: understanding storage and release with density functional theory calculations

The adsorption of 5-fluorouracil (5-FU) in zeolites is investigated with dispersion-corrected DFT calculations, with emphasis on the stabilising role of “multi-site” interactions and the behaviour of adsorbed 5-FU in the presence of water.

Metal Ions Removal from Aqueous Media Using an Electrokinetic Cell

Electro-kinetic (EK) remediation is a technique used for the treatment of contaminated soil and groundwater [1-2]. It involves the application of a low voltage-electrical current through the soil, which causes the movement of charged contaminants towards electrodes, where they can be extracted or immobilized. In EK remediation, electrodes are placed in the soil or contaminated water and connected to a power supply. In case of soil, soil need to be wetted with an electrolyte solution to facilitate the movement of charged particles. When a low voltage-electrical current is applied, it creates an electric field that drives the migration of charged contaminants, such as heavy metals ions and or charged organic pollutants, towards the opposite charge electrodes. The anode is typically made of a reactive metal, such as iron, while the cathode can be made of stainless steel or graphite. The electrodes are connected to a power supply that applies a low-voltage electrical current to the system. The contaminants can then be collected or treated using various methods, such as adsorption, precipitation, or electrochemical reactions [3-10]. EK remediation has several advantages over traditional remediation methods, such as in situ chemical oxidation and pump-and-treat systems. It can be applied to a wide range of contaminants and soil types, and is generally more effective at removing contaminants that are difficult to treat using other methods. Additionally, EK remediation can be a cost-effective and environmentally friendly option for the treatment of contaminated sites. This study explores the removal of cobalt (II) ions from aqueous solution combining the use of adsorbents such as zeolite placed in an electrokinetic cell. The most effective removing is almost 93% of cobalt (II) ions from aqueous solution after 300 minutes at 15 V in the presence of Faujasite type zeolites. Therefore, EK remediation technique has shown promise as an innovative approach to environmental remediation. References Omar H. Elsayed-Ali, Hani E. Elsayed-Ali and Tarek M. Abdel-Fattah, Journal of Hazardous Materials, 185 (2-3), 1550-1557 (2011)Alya Elsayed-Ali, Tarek Abdel-Fattah, Hani Elsayled-Ali, Hani, Journal of Chemical Education, 88(8), 1126-1129 (2011).TM Abdel-Fattah, ME Mahmoud, Chemical engineering journal 172 (1), 177-183 (2011)TM Abdel-Fattah, ME Mahmoud, MM Osmam, SB Ahmed, Journal of Environmental Science and health, part A 49 (9), 1064-1076 (2014)ME Mahmoud, TM Abdel-Fattah, MM Osman, SB Ahmed, Journal of Environmental Science and Health, Part A 47 (1), 130-141 (2012)TM Abdel-Fattah, B Bishop, Journal of Environmental Science and Health, Part A 39 (11-12), 2855-2866 (2004)ME Mahmoud, MM Osman, SB Ahmed, TM Abdel-Fattah, The Scientific World Journal 2012 (2012)ME Mahmoud, SS Haggag, TM Abdel-Fattah, Polyhedron 26 (14), 3956-3962 (2007)ME Mahmoud, AA Yakout, MT Abed El Aziz, MM Osman, TM Abdel-Fattah, Journal of Environmental Science and Health, Part A 50 (10), 1072-1081 (2015)H Namkoong, E Biehler, G Namkoong, TM Abdel-Fattah, ACS omega 7 (44), 39931-39937 (2022)

The influence of deuterium on sodium mobility and viscosity of colloidal precursor suspensions yielding template-free nanosized zeolites

The isotopic substitution in chemistry is characterized by two main effects, i.e., the kinetic isotope effect (KIE), associated with differences in the reaction rates, and the geometric isotope effect (GIE) related to crystallographic features. In this work, considering the difference in the weight of deuterium (D) compared to the weight of hydrogen (H), we use the isotopic substitution to investigate the crystallisation mechanism of template-free nanosized faujasite (FAU) type zeolite in colloidal precursors. Тhe basic hydrothermal synthesis solvent - water (H2O), is substituted with heavy water (D2O), aiming to understand the isotopic influence and the effect of H-bond networks on the zeolite crystallisation. The crystallinity, viscosity, conductivity, chemical composition, morphology and local order of the FAU zeolites synthesized in both hydrated (H) and deuterated (D) medium are evaluated with X-ray diffraction, TEM microscopy, EDX and ICP analysis, FT-IR and solid-state NMR spectroscopy. The structural directing agent - Na+, exhibits a lower mobility in the deuterated medium, because of a characteristic higher viscosity compared to hydrated medium. This leads to a slower nucleation and crystallisation in the initial stages of hydrothermal treatment in the colloidal suspensions but also to a significant difference in the Al distribution.

Photocatalytic C–H Amination of Arenes by a Ruthenium Complex on Faujasite-Type Zeolite

Photocatalytic C–H Amination of Arenes by a Ruthenium Complex on Faujasite-Type Zeolite

A comprehensive parametric study of factors that influence synthesis of high-quality ZTC using Ca2+ exchanged zeolite Y as the template

We achieved the synthesis of an ordered 3D microporous graphene architecture via chemical vapor deposition using the faujasite type zeolite as the template, i.e., “zeolite templated carbon” (ZTC). We found that implanting Ca2+ in this zeolite effectively catalyzed the growth of ZTC and greatly lowered the growth temperature. To further improve the ZTC, we investigated the influence of various synthetic parameters on its growth: Ca2+ amount, growth temperature, growth time, growth pressure, stabilization temperature and stabilization time, and describe these in detail. High-quality ZTC samples having regions of what are likely continuous single-layer carbon structures composed of trivalently bonded carbon were grown and characterized. This effective and practical synthetic method should benefit synthesis of other ZTCs and the evaluation and exploration of the structural characterization and application of ZTCs.

Exploring the framework of small pore zeolites for passive NOx adsorption

The use of a passive NOx adsorber (PNA) for NOx storage during the cold-start period is crucial for eliminating NOx emissions from the diesel exhaust. Palladium (Pd)-loaded zeolites have garnered significant attention owing to their high potential as PNA. In this study, small-pore zeolites with different frameworks were synthesized, and their structural characteristics and passive NOx adsorption abilities were investigated. Five zeolites, with CHA, AEI, AFX (low- and high- Si/Al ratio), and LEV framework structures, were synthesized by the hydrothermal conversion of faujasite-type (FAU) zeolite. Pd (1 wt%) was impregnated in combination with hydrothermal treatment. NOx adsorption and desorption behaviors were studied based on breakthrough NO adsorption and subsequent temperature-programmed desorption (TPD) experiments. Pd-loaded CHA, AEI, and LEV zeolites and high-silica AFX zeolites adsorbed approximately 93.88, 107.93, 97.57 and 106.53 μmol-NO g−1, respectively. On the other hand, the incorporation of Pd into AFX zeolite with a low Si/Al ratio led to significant hydrothermal damage and resulted in lower levels of adsorption and desorption capabilities. This demonstrates that hydrothermally stable small-pore zeolites on Pd-incorporation have great potential for passive NOx adsorption. The zeolite with different framework exhibited the different temperature range of NOx release. CHA, AEI, and high-silica AFX zeolites desorbed NOx in the low-temperature region (T < 250 °C), whereas the LEV zeolite showed a relatively high NOx desorption amount in the middle-temperature region (250 °C < T < 350 °C).

Hydrogen storage behavior of zeolite/graphene, zeolite/multiwalled carbon nanotube and zeolite/green plum stones-based activated carbon composites

In this study, novel zeolite/carbon composites were synthesized to determine hydrogen storage properties. Activated carbon (AC), graphene (GR) and multi-walled carbon nanotubes (MWCNT) were used as carbon sources in the preparation of the composites with faujasite type zeolite. AC was prepared from green plum stones by using ultrasound assisted chemical activation with the use of potassium hydroxide. In order to compare the textural and hydrogen storage properties of the prepared zeolite/activated carbon, zeolite/graphene and zeolite/multiwalled carbon nanotube composites were prepared from commercial GR and MWCNT, respectively. The structures of the obtained AC and composite samples were characterized using BET, DFT, t-plot and SEM-EDX techniques. AC was synthesized with a relatively high BET surface area (1694 m2/g), total pore volume (1.023 cm3/g) and micropore volume (0.780 cm3/g). Zeolite/activated carbon composite (ZAC) has the highest surface area, total pore volume and micropore volume, and zeolite/multiwalled carbon nanotube composite (ZNT) has the highest average pore width (6.64 nm) among all composite samples. Hydrogen sorption processes have been performed for composite samples at −196 °C and ambient pressure. The relationship between hydrogen sorption capacities, BET surface areas and pore volumes of ZAC, ZGR and ZNT composites have been investigated. The hydrogen storage capacity of the ZAC was found to be 1.3 wt%. This value is 1.47 times the hydrogen storage capacity of AC and 4.16 times the hydrogen storage capacity of zeolite. Results indicated that ZAC is a promising adsorbent for hydrogen storage.

Fe-zeolites for the adsorption and oxidative degradation of nitroaromatic compounds in water

Nitroaromatic compounds (NACs) are prominent explosives. In this context, these toxic substances were released into the environment and cause long-lasting groundwater contamination. In preparation of a possible in-situ remediation, colloidal Fe-zeolites were investigated for their capabilities as adsorbents and oxidation catalysts. It was shown that the Fe-zeolites FeBEA35 and FeFAU55 are potent inorganic adsorbents for NACs and simultaneously capable of activating H2O2 as Fenton-like oxidation catalysts. Adsorption isotherms of 15 NACs on both zeolites were measured to evaluate the option of coupling adsorptive contaminant enrichment with oxidative degradation. The faujasite-type zeolite FeFAU55 showed a distinct S-type adsorption behaviour and reached significantly higher NAC loadings of > 20 wt%. For FeBEA35, L-type adsorption isotherms and maximum loadings qmax of about 4 wt% were obtained. Degradation of all NACs, monitored by nitrate formation, was observed. Apparent rate constants of the NACs with hydroxyl radicals in a homogeneous, stoichiometric Fenton reaction were related to the heterogeneous system to examine the role of adsorption on the oxidative degradation. Beneficial influence of the adsorption on the oxidation rates was identified. The results of this work open up promising prospects for future application of Fe-zeolites for the in-situ remediation of NAC-contaminated groundwater.

Machine learning-assisted crystal engineering of a zeolite

It is shown that Machine Learning (ML) algorithms can usefully capture the effect of crystallization composition and conditions (inputs) on key microstructural characteristics (outputs) of faujasite type zeolites (structure types FAU, EMT, and their intergrowths), which are widely used zeolite catalysts and adsorbents. The utility of ML (in particular, Geometric Harmonics) toward learning input-output relationships of interest is demonstrated, and a comparison with Neural Networks and Gaussian Process Regression, as alternative approaches, is provided. Through ML, synthesis conditions were identified to enhance the Si/Al ratio of high purity FAU zeolite to the hitherto highest level (i.e., Si/Al = 3.5) achieved via direct (not seeded), and organic structure-directing-agent-free synthesis from sodium aluminosilicate sols. The analysis of the ML algorithms’ results offers the insight that reduced Na2O content is key to formulating FAU materials with high Si/Al ratio. An acid catalyst prepared by partial ion exchange of the high-Si/Al-ratio FAU (Si/Al = 3.5) exhibits improved proton reactivity (as well as specific activity, per unit mass of catalyst) in propane cracking and dehydrogenation compared to the catalyst prepared from the previously reported highest Si/Al ratio (Si/Al = 2.8).

Faujasite-Type Zeolite Obtained from Ecuadorian Clay as a Support of ZnTiO3/TiO2 NPs for Cyanide Removal in Aqueous Solutions.

In this study, zeolites prepared by the hydrothermal method from Ecuadorian clay were combined with the precursor clay and with the semiconductor ZnTiO3/TiO2 prepared by the sol-gel method to adsorb and photodegrade cyanide species from aqueous solutions. These compounds were characterized by X-ray powder diffraction, X-ray fluorescence, scanning electron microscopy, energy-dispersive X-rays, point of zero charge, and specific surface area. The adsorption characteristics of the compounds were measured using batch adsorption experiments as a function of pH, initial concentration, temperature, and contact time. The Langmuir isotherm model and the pseudo-second-order model fit the adsorption process better. The equilibrium state in the reaction systems at pH = 7 was reached around 130 and 60 min in the adsorption and photodegradation experiments, respectively. The maximum cyanide adsorption value (73.37 mg g-1) was obtained with the ZC compound (zeolite + clay), and the maximum cyanide photodegradation capacity (90.7%) under UV light was obtained with the TC compound (ZnTiO3/TiO2 + clay). Finally, the reuse of the compounds in five consecutive treatment cycles was determined. The results reflect that the compounds synthesized and adapted to the extruded form could potentially be used for the removal of cyanide from wastewater.

Binderless Faujasite Beads with Hierarchical Porosity for Selective CO2 Adsorption for Biogas Upgrading

Biomethane can be isolated from biogas through selective CO2 adsorption. Faujasite-type zeolites are promising adsorbents for CO2 separation due to their high CO2 adsorption capacity. While commonly inert binder materials are used to shape zeolite powders into the desired macroscopic format for application in an adsorption column, here we report the synthesis of Faujasite beads without the use of a binder and their application as CO2-adsorbents. Three types of binderless Faujasite beads (d = 0.4-0.8 mm) were synthesized using an anion-exchange resin hard template. All the prepared beads consisted mostly of small Faujasite crystals, as demonstrated by characterization with XRD and SEM, which are interconnected through a network of meso- and macropores (10-100 nm), yielding a hierarchically porous structure, as shown by N2 physisorption and SEM. The zeolitic beads showed high CO2 adsorption capacity (up to 4.3 mmol g-1 at 1 bar and 3.7 mmol g-1 at 0.4 bar) and CO2/CH4 selectivity (up to 19 at the partial pressures mimicking biogas, i.e., 0.4 bar CO2 and 0.6 bar CH4). Additionally, the synthesized beads have a stronger interaction with CO2 than the commercial zeolite powder (enthalpy of adsorption -45 kJ mol-1 compared to -37 kJ mol-1). Therefore, they are also suitable for CO2 adsorption from gas streams in which the CO2 concentration is relatively low, such as flue gas.

A systematic DFT screening of cationic faujasite-type zeolites for the adsorption of NO, NO2 and H2O

Unlocking the selective adsorption of NO and NO2 in presence of H2O in cationic zeolites: a systematic DFT screening of key questions and properties.

The potential of direct air capture using adsorbents in cold climates.

Global warming threatens the entire planet, and solutions such as direct air capture (DAC) can be used to meet net-zero goals and go beyond. This study investigates using DAC in a 5-step temperature vacuum swing adsorption (TVSA) cycle with adsorbents' Li-X and Na-X, readily available industrial zeolites, to capture and concentrate CO2 from air in cold climates. From this study, we report that Na-X in cold conditions has the highest known CO2 adsorption capacity in air of 2.54mmol/g. This combined with Na-X's low CO2 heat of adsorption, and fast uptake-rate in comparison to other benchmark materials, allowed for Na-X operating in cold conditions to have the lowest reported DAC operating energy of 1.1 MWh/tonCO2. These findings from this study show the promise of this process in cold climates of Canada, Alaska, Greenland, and Antarctica to be part of the solution to global warming.

Organic-Transistor-Based NO2 Sensor Fabricated with Surface-Modified Faujasite-Type Zeolite as an Efficient Nanochannel for Gas Analytes

Organic-Transistor-Based NO₂ Sensor Fabricated with Surface-Modified Faujasite-Type Zeolite as an Efficient Nanochannel for Gas Analytes