Zeolite 4A Research Articles

Spherical Binderless 4A/5A Zeolite Assemblies: Synthesis, Characterization, and Adsorbent Applications.

Zeolite microspheres have been successfully applied in commercial-scale separators such as oxygen concentrators. However, further enhancement of their applications is hampered by the post-synthetic shaping process that formulates the zeolite powder into packing-sized spherical bodies with various binders leading to active site blockage and suboptimal performance. Herein, binderless zeolite microspheres with a tunable broad size range from 2 µm to 500 µm have been developed with high crystallinity, sphericity over 92%, monodispersity with a coefficient of variation (CV) less than 5%, and hierarchical pore architecture. Combining precursor impregnation and steam-assisted crystallization (SAC), mesoporous silica microspheres with a wide size range could be successfully transformed into zeolite. For preserved size and spherical morphology, a judicious selection of the synthesis conditions is crucial to ensure a pure phase, high crystallinity, and hierarchical architecture. For the sub-2-µm zeolite microsphere, low-temperature prolonged aging was important so as to suppress external zeolization that led to a large, single macroporous crystal. For the large 500 µm sphere, ultrasound pretreatment and vacuum impregnation were crucial and facilitated spatially uniform gel matrix dispersion and homogenous crystallization. The obtained zeolite 5A microspheres exhibited excellent air separation performance, while the 4A microspheres displayed ammonium removal capabilities. This work provides a general strategy to overcome the existing limitations in fabricating binder-free technical bodies of zeolites for various applications.

Adsorptive Drying of Liquid Mixtures Containing Formaldehyde, Methanol, Water, and Poly(oxymethylene) Dimethyl Ethers on Zeolite 3A

Adsorptive Drying of Liquid Mixtures Containing Formaldehyde, Methanol, Water, and Poly(oxymethylene) Dimethyl Ethers on Zeolite 3A

Impact of varied zeolite materials on nickel catalysts in CO2 methanation

Ni catalysts supported on 4A, 5A, 13X, ZSM-5, and BEA zeolites were prepared using the vacuum-heating method for CO2 methanation. These support materials play a pivotal role in shaping the catalysts' properties and their catalytic performance. High-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectroscopy (EDS) mappings suggest a significant concentration of Ni nanoparticles situated on the external surfaces of catalysts with low Si/Al ratios zeolites (Ni-4A, Ni-5A, and Ni-13X). These Ni nanoparticles exhibit characteristics of weaker metal-support interaction, lower metal reduction temperatures, and moderate H2 adsorption activity. Moreover, these low Si/Al ratio zeolites demonstrate robust CO2 adsorption activity. These properties endow Ni-5A and Ni-13X catalysts with heightened CO2 conversion (70.4–70.9%) and methane selectivity (92.4–96.4%). In contrast, high Si/Al ratio zeolite-based catalysts (Ni-ZSM-5 and Ni-BEA) exhibit smaller Ni particles, strong metal-support interaction and weaker CO2 adsorption activity, resulting in reduced CO2 methanation activity and decreased methane selectivity (71.2–73.4%). The normalized CO2 conversion rate presents a correlation with the average Ni particle size.

Synthesis of hydrophobic CuCl/LaA modified by butyltrichlorosilane towards enhanced CO adsorption under humid environment

Cuprous ion modified molecular sieves have been considered as promising CO adsorbents in gas separation or purification industry. However, it persists as a significant challenge to overcome the unfavorable effect of water vapor in the work environment on gas adsorption and separation. Herein, we propose a synthetic strategy using rare earth element La as an additive to form LaOLa coordination bonds followed by surface silanization treatment to construct a hydrophobic SiOSi barrier to significantly improve the stability of Cu+ under humid atmosphere. By successively introducing La3+ and Cu+ into zeolite 5A, CuCl/LaA adsorbents were prepared via ion exchange and solid dispersion methods. And then by silanization modification using toluene as solvent and butyltrichlorosilane (BTS) as hydrophobic agent, hydrophobic CuCl/LaA-BTS adsorbents were prepared. Dynamic adsorption investigation demonstrated that the as-prepared CuCl/LaA-BTS adsorbents possessed hydrophobic surface and consequently the adsorption capacity of CO was enhanced significantly under humid atmosphere. The CO adsorption breakthrough capacity over CuCl/LaA-BTS attained 0.34 mg/g, which was 5.7 times higher than that of zeolite 5A at 40 °C, atmospheric pressure and a relative humidity of RH = 55 %. Moreover, the CO adsorption capacity of CuCl/LaA-BTS retained 0.31 mg/g after four cycle regenerations. This work provides an effective and novel route for synthesizing highly stable cuprous ion modified zeolite adsorbents.

Efficient treatment of veterinary pharmaceutical industrial wastewater by catalytic ozonation process: degradation of enrofloxacin via molecular ozone reactions.

The study focused on the efficacious performance of bimetallic Fe-Zn loaded 3A zeolite in catalytic ozonation for the degradation of highly toxic veterinary antibiotic enrofloxacin in wastewater of the pharmaceutical industry. Batch experiments were conducted in a glass reactor containing a submerged pump holding catalyst pellets at suction. The submerged pump provided the agitation and recirculation across the solution for effective contact with the catalyst. The effect of ozone flow (0.8-1.55mg/min) and catalyst dose (5-15g/L) on the enrofloxacin degradation and removal of other conventional pollutants COD, BOD5, turbidity was studied. In batch experiments, 10g of Fe-Zn 3A zeolite efficiently removed 92% of enrofloxacin, 77% of COD, 69% BOD5, and 61% turbidity in 1L sample of pharmaceutical wastewater in 30min at 1.1mg/min of O3 flow. The catalytic performance of Fe-Zn 3A zeolite notably exceeded the removal efficiencies of 52%, 51%, 52%, and 59% for enrofloxacin, COD, BOD5, and turbidity, respectively, achieved with single ozonation process. Furthermore, an increase in the biodegradability of treated pharmaceutical industrial wastewater was observed and made biodegradable easily for subsequent treatment.

A novel and cost-effective synthesis of magnetic zeolite 4A using kaolinite and red mud for Sr(II) removal

A novel and cost-effective approach was successfully developed for synthesizing high-performance zeolite 4A encapsulating magnetic particles (magnetic zeolite 4A) using kaolinite and red mud as raw materials via one-step combined activation-reduction and subsequent hydrothermal synthesis. The concurrent reduction of iron compounds in red mud to magnetic particles mainly composed of Fe3O4 during the thermal activation of kaolinite eliminated the need for a distinct red mud reduction process, thereby streamlining the synthesis and maximizing efficiency. The resulting product comprised highly crystalline zeolite 4A encapsulating magnetic particles derived from the red mud, avoiding oxidation and corrosion of the magnetic material in acidic solutions. A series of magnetic zeolite 4A (MZ) were obtained by introducing varying percentages of red mud and kaolinite, and their morphological, structural, magnetic and adsorption properties were investigated. The BET specific surface area of the obtained MZ-20 is 13.6 m2/g. MZ-20 (red mud: kaolinite mass percentage is 20%) displayed the maximum adsorption capacity of 172 mg/g for Sr(II). Within 1 h, 96.4% of the Sr(II) was removed. The adsorption kinetics and isotherms followed the pseudo-second-order and Langmuir models, respectively. Using a mixed 0.1 M NaCl and 0.1 M HCl solution as eluent, the magnetic adsorbent maintained high desorption and regeneration ratios along with stable magnetic properties after four adsorption-desorption cycles. In summary, the MZ-20 adsorbent exhibited high adsorption capacity, recyclability and excellent magnetic properties, making it a decontamination candidate for removing Sr(II) from radioactive wastewater.

Design and Development of Sustainable Polyurethane Foam: A Proof‐of‐Concept as Customizable Packaging for Cultural Heritage Applications

World cultural heritage is an invaluable resource and must be preserved. Conventional packaging materials, such as polystyrene, polyurethane (PU) foams, paper‐like tissue, and nylon fabric, are petrol‐based. According to Agenda 2030, and Green Deal directives, the development of alternative bio‐based materials has gained significant scientific and technological relevance. In this scenario, a new sustainable packaging material for safe storage and transporting of the artifacts, based on a sustainable PU foam filled with 6 wt% of Zeolite 4A, is proposed. Zeolite 4A dispersion into PU matrix imparts higher compression strength and energy absorption capability with respect to unloaded materials (7‐fold increase), owing to its remarkable cell nucleating effect. The proposed foam can adsorb water vapor, up to 29 wt%, thus contributing to regulating the humidity around the artifact. A remarkable advantage of the developed foam is the possibility to use it as plaster for precisely casting the article to protect, resulting in strongly improved handling, protection, and transportation safety with respect to conventional packaging solutions. A proof‐of‐concept workflow is proposed, consisting of: 1) three‐dimensional (3D) scanning of the original artifact; 2) its replication through 3D printing; 3) the use of such a replica to prepare a tailored cast of the artifact shape.

Preparation and thermal properties of zeolite/MgSO4 composite sorption material for heat storage

Thermochemical sorption heat storage based on salt hydrates offers the potential advantages such as high energy density, negligible heat loss, small volume change and flexible working modes. Magnesium sulphate (MgSO4) is a high energy density hydrated salt available for the thermochemical sorption heat storage. In this work, different types of zeolites (including 3A, 5A and 13X zeolites) have been selected as mass-transfer-enhancing and structural stabilizing materials, and a series of zeolite/MgSO4 composites have been fabricated. To investigate the thermal energy storage performance of zeolite/MgSO4 composites, the properties of the composites, such as micro-morphology, pore structure, chemical composition and sorption-desorption behavior, have been characterized and analyzed. Results indicated that the mass transfer performance of the composite materials is significantly better than that of the pure zeolites. As the mass fraction of MgSO4 in the composite sorbents increases, the specific surface area and porosity of the composite sorbent decreases, and the sorption performance has been enhanced. Compared with 3A zeolite-based and 5A zeolite-based composites, 13X zeolite/MgSO4 composite materials show the best heat storage performance. At the condition of 25 °C and 60% RH, the 13XM20 has the highest sorption capacity of 0.21 g/g, which is 24% higher than that of pure zeolite 13X. Accordingly, the maximum heat storage density is 438.4 kJ/kg, which exhibits the superior heat storage performance among of the hydrated salt sorbents. The potential of 13X zeolite/MgSO4 as sorption heat storage material in efficient utilization of solar heat and low-grade industrial waste heat has been revealed.

Pb/Pb3O4 Metal-Semiconductor Nanocomposite Obtained on 4A Zeolite-Optical and Structural Properties.

This work describes a controlled and low-cost synthesis method to obtain Pb/Pb3O4 nanocomposites using synthetic zeolite 4A. The nanostructures obtained have a core-shell configuration with 5-25 nm diameters. High-resolution transmission electron microscopy (HRTEM), BF, high-angle annular dark-field annular scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible (UV-vis) characterization techniques were used. Crystallographic planes (111), (200), and (220) for the core and planes (110) and (211) for the shell, corresponding to FCC and tetragonal structures for Pb and Pb3O4, respectively, were determined using HRTEM. The HAADF-STEM images allowed the analysis of intensity contrast images proportional to the number of atoms. XPS spectral analysis showed a 4.8 eV difference in binding energy between Pb 4f7/2 and Pb 4f5/2 for lead and lead oxide. EDS elemental mapping, XPS, and UV-vis spectroscopy analyses revealed the simultaneous presence of lead and lead oxide in the same structure. The band gap obtained for the shell was determined to be 4.50 eV. Consequently, Pb/Pb3O4 nanocomposites show a higher response to high-energy photons, making them suitable for UV photocatalysis applications.

Efficient removal of pharmaceutical contaminant in wastewater using low-cost zeolite 4A derived from kaolin: Experimental and theoretical studies

The present report describes the easy preparation of zeolite 4 A from Cameroonian raw kaolin using a hydrothermal method. Highly crystalline, microporous pure-phase zeolite 4 A with cubic morphology was confirmed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (MAS-NMR), Thermogravimetric analysis and N2 adsorption-desorption. The synthesized zeolite 4 A was applied as an adsorbent for the effective removal of ciprofloxacin in aqueous solution. Subsequent adsorption mechanism and interactions between ciprofloxacin and the surface of zeolite 4 A (001) was studied using density functional theory (DFT) and Monte Carlo molecular simulation. The maximum elimination efficiency by zeolite4A under optimal conditions with a contact time of 80 min, pH = 8, the ciprofloxacin concentration of 60 ppm and with an adsorbent mass of 20 mg at 25 °C was 91.75 %. The adsorption of ciprofloxacin by zeolite 4 A followed the pseudo-second order kinetic model and the Langmuir isotherm. The maximum adsorption capacity (qmax) calculated with the Langmuir model was 87.72 mg/g with a value of the linear regression coefficient R2 of 0.9634. Positive ΔH values suggest an endothermic adsorption reaction. However the negative values for adsorption energy (Eads) and ΔG showed that adsorption was spontaneous. Experimental and theoretical results indicated the predominance of chemisorption during the adsorption. Zeolite 4 A had good stability and recyclability and achieved a high removal efficiency of 85.68 % for ciprofloxacin after seven consecutive adsorption cycles within optimal conditions. Zeolite 4 A could be recommended as an effective adsorbent for the removal of ciprofloxacin from wastewater.

Surface Aerophilicity Engineering of Heterogeneous Catalysts for Enhanced Catalytic Ozonation

AbstractHeterogeneous catalysts for catalytic ozonation are elaborately designed with commendable intrinsic activity, while their industrial applications are limited by inadequate mass transfer of ozone (O3). In this work, it is demonstrated that engineering the surface aerophilicity of heterogeneous catalyst enables fast mass transfer of O3 reactant, giving rise to much enhanced catalytic ozonation performance. Taking active 4A zeolite catalyst as an example, the aerophilicity of spherical 4A zeolite can be greatly enhanced by coating polytetrafluoroethylene (PTFE) with low surface energy, and the optimized sample exhibits a 99.5% removal of atrazine (ATZ) within 20 min (corresponding to a k of 0.269 min−1), much better than 4A zeolite without surface aerophilicity engineering (k≈0.156 min−1). The PTFE coating does not change the ozone activation mechanism and degradation pathways for ATZ, further demonstrating that the enhanced ozonation activity is attributed to the enhanced mass transfer process. In addition, the general applicability of this surface aerophilicity and the potential ozonation application for industrial wastewater treatment are both demonstrated.

The impact of trace amounts of CO2 on the high-pressure adsorption of CH4 on 5A zeolite

The impact of trace amounts of CO2 on CH4 adsorption in a zeolite at elevated pressure was examined using experimental, binary adsorption isotherms, and molecular simulations. CH4 upgrading is important for a variety of applications, and the use of zeolites for CH4 upgrading has been considered previously but, to the best of our knowledge, not at pressures between 60 and 70 bar. The non-ideality of the adsorption was examined by comparing the experimental loadings to predicted loadings from the Ideal Adsorbed Solution Theory (IAST). When adsorption occurs at a total pressure of 58–66 bar, and a CO2 fraction below 0.42 mol %, there was less than 5 % error in the CH4 IAST predicted loading compared to the experimental value, but the deviation in CO2 loading between IAST and experiments, even at these low CO2 mole percentages, varied nominally from 4 to 13 %. Above 0.42 mol % deviations from IAST were more severe. Grand Canonical Monte Carlo simulations captured the trends in the adsorption data and illustrated how CO2 molecules align in the pore when adsorbed such that oxygens on both ends of the molecule can interact with cations in the zeolite. The results highlight the applicability of adsorbent materials to separate CO2 from process streams at elevated pressure and provide molecular insights that can aid the design of adsorbent structures.

Hand warmer types, silica and zeolite 4A as potential hand warmers

Hand warmer types, silica and zeolite 4A as potential hand warmers

Extraction of silica from sugarcane bagasse ash and its utilization in zeolite 4A synthesis for CO2 adsorption.

Sugarcane bagasse ash (SCBA) is a solid waste containing a high amount of silica (SiO2) and is suitable to utilize as a silica source for synthesizing zeolite NaA. SCBA is typically calcined at high temperatures before silica extraction. The method is not environmentally friendly because it consumes energy and produces CO2. This work demonstrates an alternative extraction method of SiO2 from SCBA by treating it with hydrochloric (HCl) and sodium hydroxide (NaOH) solution. The obtained mixture was separated by paper filter No. 1 (P) and a combination of paper filter and syringe filter (PS). The solution was neutralized by HCl solution, producing silica (SiO2-P and SiO2-PS) with a purity of 98 wt%. Both SiO2 samples and SCBA were utilized to synthesize zeolite NaA for CO2 adsorption. The CO2 adsorption capacities of NaA-P and NaA-PS were 4.30 and 4.10 mmol gadsorbent -1, in the same range as commercial NaA. The capacity is influenced by the total basicity of zeolite. The CO2 adsorption behavior of all samples correlates well with the Toth model. The CO2 adsorption kinetics agrees well with the pseudo-second-order kinetic model. Overall, this work shows the successful extraction of silica via using a direct NaOH solution, yielding high-purity silica sufficient for synthesizing zeolite NaA, a promising adsorbent of CO2.

Preparation of 4A zeolite modified enteromorpha biochar and its application in bacillus thuringiensis microspheres

The Enteromorpha prolifera biochar and 4A zeolite-modified biochar based on different pyrolysis temperatures were prepared. The biochar of good biocompatibility with Bt was selected by studying the effects of different biochar on the survival rate and salt tolerance of Bacillus thuringiensis (Bt). The biochar microspheres loaded with Bt were prepared with sodium alginate, pectin, and chitosan. The effects of the addition of biochar on the particle size and ball formation rate of the microspheres were investigated. The structure of the microspheres was characterized by SEM and FTIR, and the SR of the microspheres under different pH conditions were evaluated. The results showed that 4A zeolite-modified biochar prepared at 500 ℃ (GH500) had good compatibility with Bt, and could improve the salt tolerance of Bt. The prepared microspheres have a uniform shape and particle size, and their swelling characteristics were pH-responsive, the microspheres containing biochar exhibited good swelling properties under alkaline conditions.

LTA zeolites as catalysts for transesterification of glycerol with dimethyl carbonate

The objective of this study was to investigate the use of LTA-structured zeolites as catalysts for synthesizing glycerol carbonate through the transesterification of glycerol with dimethyl carbonate, under mild reaction conditions. To evaluate the catalysts, a range of characterization techniques, including XRD, AES, SEM, TPD-NH3, TPD-CO2, and FT-IR with probe molecules like pyridine and pyrrole, along with elemental analysis, were employed. The investigation focused on various forms of LTA-structured zeolites (with K, Na, and Ca cations) to assess their impact on transesterification activity, with particular attention to the type of ion utilized and their basicity. Among these zeolites, K-Na-LTA (3A) zeolites demonstrated the most promising performance, achieving glycerol conversion rates ranging from 55 % to 77 %. Moreover, increasing basicity in the 3A zeolites led to higher glycerol conversion and glycerol carbonate yield. Encouragingly, all tested samples exhibited 100 % selectivity, exclusively producing the desired glycerol carbonate. However, during catalyst recycling, the decrease in glycerol conversion was observed, likely due to the leaching of active sites from the catalyst into the reaction medium. Methanol, being a one of the products, was identified as a potential agent responsible for the removal of potassium ions, during this process.

MICRO-SCALE CONTINUOUS CO2 ADSORPTION COLUMN DESIGN WITH ZEOLITE 5A ADSORBENT

CO2 is the primary greenhouse gas which mainly stems from human activities. Increased CO2 emission in the atmosphere promotes global warming, which adversely affects human health and the environment. Adsorption is proposed as one of the practical and economical methods for CO2 removal. Zeolite 5A is an adsorbent that can be employed in CO2 adsorption due to its high porosity and adsorption capacity. In this study, we investigate the CO2 adsorption behavior by zeolite 5A adsorbent in a continuous, micro-scale fixed-bed column at different bed heights. Gas chromatography was utilized to determine CO2 exit concentrations. The column pressure drop was calculated using Ergun's equation. The obtained data were analyzed in the form of breakthrough curves, then fitted to Thomas and Yoon-Nelson's mathematical model to obtain adsorption rate coefficient in the column. The experimental data of CO2 adsorption by zeolite 5A shows the good correspondence with both Thomas’s and Yoon-Nelson’s mathematical models. At a flow rate of 30 mL/min and bed height variations of 10 and 12 cm, the CO2 adsorption capacities (q0) were 0.0071 and 0.0099 mol/g, respectively. While the Thomas’s adsorption rate coefficient, kTH, for the same conditions were 0.4164 min-1 and 0.4342 min-1.

Unraveling the sorption mechanisms of ciprofloxacin on the surface of zeolite 4A (001) in aqueous medium by DFT and MC approaches

The adsorption mechanism of ciprofloxacin (CIP) and its ionic form were investigated using density functional theory (DFT) and molecular dynamics (MD), with the goal of forecasting their adsorption behavior in terms of gap energy, global reactivity descriptors, Fukui functions, adsorption energies, and density of state on the surface of zeolite 4A (001). Quantum chemical parameters related to the adsorption process were calculated, as well as the overall reactivity. According to DFT calculations, the zwetterionic form CIP± are the most stable and reactive and have a greater power of electron transfer compared to the other species. Under aqueous conditions, zeolite can adsorb ciprofloxacin (CIP) and its ionic forms, as revealed by molecular dynamics simulation. Ciprofloxacin in the zwitterionic form (CIP±) were more efficiently adsorbed to the surface of zeolite 4A (001) than the cationic (CIP+), anionic (CIP−), and neutral(CIP) forms; through the evaluation of adsorption energy, probability distribution, interaction, and density of state. The results also demonstrated that the compounds studied were adsorbed via the process of chemical bonding, which was confirmed by the negative values of the interaction energy. Furthermore, the negative adsorption energy values suggest a significant adsorption of all compounds, with electrostatic interactions (physisorption), diffusion into the pores, and n-π bonds (chemisorption) on the zeolite surface. The increase in adsorption energies and the proximity of the molecules studied to the zeolite surface indicate the predominance of chemisorption, and the adsorption of ciprofloxacin was found to be an exothermic and spontaneous process. Molecular dynamics (MD) modeling was in agreement with the DFT results.

Mass transport, kinetic model, and application of CO2 adsorption on zeolite 5A granules

AbstractEnvironmental damage ranges from soil degradation, air pollution, and wastewater from human‐induced activity. In this study, to reduce CO2 emission, zeolite granules were prepared manually. In addition, the mass transfer and kinetic adsorption were analyzed to understand the mechanism of CO2 adsorption using mathematical models. We studied the effects of amount of binder, temperature, granule size, and flow rate of CO2 on efficient CO2 adsorption on zeolite 5A granules of different sizes (3–4 and 6–7 mm). The kinetics of CO2 adsorption and mass transfer of zeolite 5A granules were evaluated for the rate‐limiting step. The results showed that decreasing the temperature and the amount of binder increased the CO2 adsorption capacity. We observed the highest CO2 adsorption capacity of 2.84 mmol g−1 at 298 K with 4 wt% of the binder at a flow rate of 2 L h−1. The pseudo‐first‐order sorption behavior was the best model with R2 > 0.9832, whereas the root mean square error model showed an R2 < 0.2136. The Biot number and film diffusion model were used to investigate the importance of external mass transfer on intraparticle diffusion. It was confirmed that the adsorption on sustainable zeolite 5A granules was controlled by film diffusion.

Kinetic effect of in situ water adsorption during CO2 hydrogenation: An experimental investigation

Sorption enhancement exhibits great potential as process intensification strategy to improve the extent of chemical reactions.Particularly, the selective removal of products or inhibiting components from the reactive gas mixture via in situ adsorption ontosolid sorbents may reducethermodynamic and kinetic constraints. Consequently, the present work investigates the kinetic effect of sorption-enhanced CO2 hydrogenation via dynamic experimentation under reaction conditions in the kinetic regime with sufficient distance from chemical equilibrium. In particular, H2O is selectively removed by adsorption at 280 and 330 °C and 2 bar on zeolite 3A. The experimental data are evaluated based on stoichiometric analysis for quantification of the kinetic effect of in situ water removal on CO2 hydrogenation. The results reveal that an improvement in reaction extent is obtained, which is caused by enhancement of the reaction rate in the kinetic regime, probably due to the less pronounced blockage of catalytic sites by water adsorption.