NaA Zeolite Research Articles

Amine-free synthesis of fly ash based ZSM-5 via interzeolite transformation with related investigation of mechanism

Fly ash is a solid waste consisted of SiO 2 , Al 2 O 3 , CaO, Fe 3 O 4 and trace amounts of heavy metal (Hg and Cd), therefore, their disposal could pose some threats to the environment. In this paper, the interzeolite transformation of NaA to ZSM-5 was explored as a low-cost and high value-added green process, where fly ash was resource utilized, and the conventionally high-cost silicalite-1 seeds and high-contamination organic amine were not required. Firstly, fly ash was activated with NaOH at high temperature, followed by the alkali-dissolving purification to remove the impurities. Then, purified fly ash was utilized to synthesize NaA at 110 °C for 12 h, and the transformations of NaA to ZSM-5 were conducted and the process parameters were optimized such as crystallization temperature, duration time, the content of additives such as ethanol or sodium chloride and the pretreatment of NaA, and so on. The results showed that the introduction of a trace amounts of NaCl or EtOH could greatly facilitate the growth of ZSM-5, and the high crystalline ZSM-5 molecular sieves were successfully obtained at 160 °C for 36 h with the comparable textual properties to the commercial ZSM-5. Finally, an assembly mechanism of MFI framework in the interzeolite transformation of NaA to ZSM-5 was proposed. • Fly ash was alkali-melting activated followed by the alkali-dissolving purification. • High-pure and high-active fly ash was used as raw materials to synthesize NaA zeolite. • Amine-free synthesis of ZSM-5 was conducted via interzeolite transformation of NaA assisted with NaCl or EtOH. • A transcrystal mechanism was proposed of synergistic structural guiding effects of NaA and four-coordinate Na + .

Ethanol dehydration performance of three types of commercial-grade zeolite permselective membranes.

Many organic solvents form difficult-to-separate mixtures with water and have an affinity for water, making drying a potential reuse prerequisite. Pervaporation (PV) and vapor permeation (VP) membrane technologies hold promise for energy-efficient solvent drying. Several water-selective membrane materials are commercially available, but performance data is limited, particularly for two recently commercialized membrane materials: chabazite (CHA) and T-type zeolites. In this work, commercial-grade samples of CHA and T-type membranes, along with a NaA zeolite membrane, were evaluated for the removal of water from ethanol. The CHA sample had the highest initial PV water permeance (6820 GPU) and water permselectivity (3430) with 5 wt% water in ethanol at 50 °C. Initial NaA membrane performance was slightly lower (6060 GPU and 3260), while the T-type membrane had the lowest initial permeance and selectivity (4260 GPU and 1090). Performance declined over time, most notably for the NaA membrane, for which water permeance fell over 50% through 39 days of testing. The T-type membrane exhibited the steadiest PV water permeance, but the most variable ethanol permeance. The PV performance of the three membranes largely overlapped the predicted range for T-type membranes. That performance generally exceeds the anticipated ethanol drying performance of non-zeolitic PV membranes but is less than that predicted for NaA and CHA membranes. The present CHA membrane results, along with other recent reports, refine earlier predictions of the ethanol dehydration performance of that type of zeolite. The changing performance with time should be understood to properly design a solvent dehydration system.

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H 2 O 2

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H ₂ O ₂

Interzeolite Conversion-Synthesized Sub-1 μm NaA Zeolite Membrane for C2H2/C2H4 Selective Separation.

Zeolite membranes with reduced thickness and high continuity are of paramount importance for accelerating selective gas separation for resemblant molecules, and the synthesis of such membranes remains a grand challenge. Herein, we developed an interzeolite conversion synthesis approach to grow NaA zeolite membranes on NaX. The conversion of NaX into NaA proceeded via mild hydrothermal treatment of a dilute synthesis solution, preferentially forming a continuous polycrystalline NaA layer on the surface of NaX, which was precrystallized on a porous alumina support. The thickness of the NaA zeolite membrane was successfully controlled to the submicron scale (500 nm). The synthesized NaA membrane functioned as a selective separator for C2H2 and C2H4 gases. Taking the traditionally in situ grown membrane as a reference, the interzeolite-derived membrane exhibited a 3.5-fold separation factor and ∼4.0 times C2H2 permeance. This approach provides an alternative synthesis option for zeolite membranes with advanced properties, and high efficiency in terms of superior gas selectivity and permeability is promising in precise gas separation.

Influence of the SiO2/Al2O3 molar ratio on the specific properties of NaA zeolite

The aim of this research was to determine the influence of the SiO2/Al2O3 molar ratio on the specific commercial properties of NaA zeolite subtypes as final market products (4A,4A-AG and 4A-MS) under the real production and process conditions. The value of the SiO2/Al2O3 molar ratio, so-called silicate module, was set as independently variable and the effect on the physical and chemical properties of each of the subtypes of NaA zeolites was examined.The paper investigates how the SiO2/Al2O3 molar ratio affects specific properties of NaA powders, namely the ion exchange capacity, oil adsorption capacity and water adsorption capacity. Some previous theoretical and experimental studies have shown that the molar ratio plays a crucial role in the formation of these very similar but for final application different subtypes of NaA zeolite. The experimental part of this work was performed and tested in real production conditions, which can be considered as an advantage in relevance to the obtained results. Various analytical and instrumental testing methods were used for the analysis of the obtained powders, including SEM, XRD and PSD analyses.

Impact of ion exchange on zeolite hydrophilicity/hydrophobicity monitored by water capacity using thermal analysis

Zeolite coatings consisting of a mixed phase of LTA and FAU type zeolites, prepared originally in Na form, were exchanged by Li, Mg and Ce ions. The effects of ion exchange on hydrophilicity/hydrophobicity as well as water capacities at relatively low and high temperatures were investigated by thermogravimetry (TG). The same investigations were also carried out for pure phases of powder zeolites NaA, NaX and NaY. It was determined that ion exchange might have significant effects on hydrophilicity/hydrophobicity and water capacities of zeolites in case favorable ions and suitable exchange conditions are used. Enhancements of about 50% were obtained in the hydrophobicity index and water capacity values at 100 °C when zeolite coatings in Na form were exchanged by Ce and Mg, respectively. The improvements obtained by Mg and Ce exchanges were determined to be related to different effects of these ions on LTA and FAU type zeolite phases, respectively.

H2S adsorption using ZnO modified Na-A zeolite and conditions optimization by Response Surface Methodology

Zinc oxide-impregnated Na-A zeolites were synthesized and used in sour gas treatment for hydrogen sulfide (H2S) removal. Response Surface Methodology (RSM) was used to study the effect adsorption variables, on the adsorbent adsorption capacity. Box– Behnken design of experiment was selected and quadratic regression was used to describe the relationship between the process variables and the adsorbent adsorption capacity. The effects of three process variables of A: reaction temperature (28, 64 and 100 °C), B: inlet H2S concentration (111, 142 and 200 ppm), and C: inlet flow rate (20,30 and 40 mL min–1) on the adsorbent adsorption capacity were investigated. ANOVA was used to analyzed the interaction between the process variables and response factor. The result showed that all studied factors are significant for H2S removal. Analysis of variance implied the selected model was fitted with the experimental data. The result indicates that up to 31.07 mg S/g adsorbent can be obtained at optimum conditions.

Selection of a favorable zeolite for solar adsorption cooling: How straightforward is it?

A theoretical investigation was carried out for determining the performances of NaX, LiX, NaA, NaY, SAPO-34 and FAPO-5 zeolites used as coatings in solar adsorption cooling systems. The regeneration temperatures of the zeolites varied in a broad range. The daily temperature variation of the zeolite adsorbent and the power of the solar adsorption cooling system were calculated for each zeolite by using different coating mass and wind speed values. It was determined that for the summer weather conditions investigated, the regeneration temperature of the zeolite had strong impact on the performance of the solar adsorption cooling system. The aluminophosphates, often considered as very suitable for adsorption heat pump and cooling systems due to their quite low regeneration temperatures, generally had lower performances while the aluminosilicates with higher regeneration temperatures performed much better. This was related to the relatively high minimum adsorbent temperature in the system using solar energy, resulting in quite lower amount of water circulation for the adsorbents with relatively low regeneration temperatures. It was also determined that using different amounts and types of zeolite affected the operating period of the solar cooling system, as well as the power along the daily cycle.

Magnetic clustering of weakly interacting Ni-ions in Ni-exchanged zeolites

Divalent Nickel cations were incorporated in two commercial zeolites (Na-A zeolite and Na-X zeolite) by a process of ionic exchange marginally affecting structure, morphology and porosity of the host materials, as verified by XRD, HRTEM and physisorption measurements. Comparable amounts of magnetic ions were introduced (4.80 wt% in Na-A zeolite and 6.20 wt% in Na-X zeolite), as checked by AAS and TGA. Magnetic measurements were done between 2 and 300 K using a SQUID magnetometer up to 70 kOe. The initial susceptibility follows the Curie–Weiss law with Curie temperatures θ of 10.3 and 11.5 K. The effective magnetic moments on Ni2+ ions suggest almost complete quenching of the angular momentum. No long-range magnetic order is found below θ; however, FC/ZFC magnetization curves indicate the formation of superparamagnetic clusters of magnetic ions with blocking temperature of about 6.5 K in both zeolites. Cluster size, average number of clustered ions, effective anisotropy of clusters are evaluated. A comprehensive picture of all magnetic effects taking place over the whole temperature range is drawn by combining magnetic, structural and morphological data.

Synthesis of NaA Zeolite from Blast Furnace Slag (BFS) and Its Utilization for Adsorption of Basic Dye (Methylene Blue)

The adsorption process of methylene blue (MB) onto blast furnace slag (BFS) based zeolite (BFSZ) was discussed. Via the analyses of XRD, FE-SEM, XRF, CEC and SSA, the main composition in in the product was Na-A zeolite. And the Na2O content, CEC value and SSA value of the BFSZ samples was significantly increased to 19.61 wt.%, 3.06 meq/g and 27.55 m2.g1 respectively. Moreover, the adsorption kinetic for MB onto BFSZ was examined and best represented by Pseudo-second-order kinetic model. Moreover, the adsorption capacity of MB from aqueous solutions reaches up to 21.89 mg.g1 at 30 °C.

A novel preparation of high permeation SiC supports for NaA zeolite membrane by in situ reaction bonding

The performance of zeolite membrane supports directly determines the synthesis performance and industrial application of zeolite membranes. In this study, a novel and high permeation SiC supports for NaA zeolite membrane were prepared by carrying out in situ reaction bonding at high temperature in the air atmosphere to coat the SiC particles with aluminum sol. The effects of process parameters on the formation of porous structure of SiC supports were systematically investigated, and the underlying mechanism was explored. During the sintering process, high-temperature Al2O3 from aluminum sol reacted with SiO2 generated by oxidation of the surface of SiC particles to form mullite, which exhibited excellent chemical stability and improved the mechanical properties and chemical stability of the supports. The porous SiC supports for zeolite membrane displayed obvious three-dimensional connected pore structure, with smooth inner surface of the pores and obvious connection neck between the particles. The porous SiC supports for zeolite membrane showed good in situ mullite bonding between the particles, and high permeability. It has a porosity of 36.3%, an average pore size of 1.42 µm and a bending strength of 32.4 MPa. All these figures indicate good comprehensive properties that are consistent with the rigorous requirements of zeolite membrane synthesis and industrial application.

Sulfur-modified zeolite A as a low-cost strontium remover with improved selectivity for radioactive strontium

Selective removal of radioactive strontium (90Sr) from the environment is important, and selective adsorption/ion exchange is appropriate for removal of trace amounts of 90Sr from large volumes of 90Sr-contaminated water. Although various inorganic ion-exchange materials, including zeolites, have been investigated intensively for removal of Sr2+ due to their excellent resistance to radiation and high ion-exchange capacity, their ion-exchange selectivity for Sr2+ is poor in the presence of competing ions such as Ca2+ and Mg2+. Here, sulfur-modified NaA zeolite (S-NaA) was prepared for low-cost, selective 90Sr removal because the elemental sulfur encapsulated in micropores provides additional Lewis acid-base interactions with Sr2+ during the Sr2+ ion-exchange. Our ion-exchange experiments revealed that S-NaA with 3 wt% sulfur (3 S-NaA) showed the highest Sr2+ selectivity among various S–NaAs containing up to 10 wt% sulfur because ion exchange involving bulky hydrated Sr2+ depends on the reduced micropore volume of S-NaA after sulfur loading. Most importantly, 3 S-NaA effectively and efficiently (>99.4%) removed 90Sr from groundwater containing 8.4 ppt 90Sr, demonstrating its excellent potential for practical application in the treatment of 90Sr-contaminated water.

Insight into the liquid adsorption of tobacco specific nitrosamines on ZIF-8

Liquid adsorption of TSNA by ZIF-8 was studied in this paper for the first time, applying the deformable molecular sieve to adsorb and separate TSNA. ZIF-8 can adsorb the bulky NNK molecules whose size exceeds its pore size, whereas NaA and KA zeolites cannot though they have similar pore sizes. Moreover, ZIF-8 selectively adsorbed NNK in solution and reached adsorption equilibrium within 5 min. In contrast, NNN was hard to be adsorbed and easy to be eluted by water, which is useful for the separation of TSNA. The influence of solid-liquid (S/L) ratio and other factors on TSNA liquid adsorption was investigated in detail. When S/L was 0.2, ZIF-8 exerted the highest efficiency and the adsorption capacity per unit surface area reached 12–15 nmol. Through the comparison of adsorption of NNK, NNN and NPYR, it is found that the adsorption of TSNA by ZIF-8 depended on π-π electron interaction mainly, rather than geometric confinement effect. The liquid adsorption curve of NNK conforms to Langmuir isothermal adsorption model, and its saturated adsorption capacity Qm was estimated to be 4.34 mg g−1, but actually it could reach 3.19 mg g−1 only. In addition, ZIF-8 had a mixing effect in liquid adsorption of TSNA: the presence of NNK promoted the adsorption of NNN slightly. ZIF-8 has the characteristics of fast adsorption and easy elution of TSNA in solution, which is beneficial for removal of TSNA to protect the environment and public health.

Rubik’s cube shaped organic template free hydrothermal synthesis and characterization of zeolite NaA for CO2 adsorption

Here in this work a simple and direct method to synthesize Rubik’s cube-like Linda Type (LTA) zeolite NaA structure is reported. Linda Type (LTA) zeolite was synthesized by hydrothermal method without using any organic template additives. The molar ratio of 3.165Na2O:Al2O3:1.926SiO2:128H2O have been used to prepare the zeolite NaA hydrogel. The thermal stability of the synthesized zeolite NaA was studied through the thermogravimetric analysis (TGA). The results of X-ray diffraction (XRD) analysis showed that the crystallinity of the synthesized zeolite is good and the material is of high purity. Through the FTIR study, functional groups belonging to the zeolite NaA was confirmed. From the FESEM analysis, morphology of the synthesized sample was found to be Rubik’s cube-like structure. The elemental composition of the material was studied using the EDAX analysis and the ratio of Si:Al was found to be ∼ 1. Further from the SAED patterns of the prepared sample, it was observed that the material is polycrystalline in nature. From the nitrogen adsorption/desorption results the zeolite NaA samples was found to be mesoporous in nature. The pore size of the samples have been obtained using the Barrett-Joyner-Halenda (BJH) analysis. The CO2 adsorption isotherm study was carried out at 298 K and the isotherm was fitted by using Langmuir and Freundlich adsorption isotherm.

Low-temperature sintering of silicon carbide membrane supports from disks to single- and 19-channel tubes

As the configuration of asymmetric ceramic membranes is determined by the membrane supports, a low temperature sintering process was developed to prepare ceramic membrane supports from disks to single- and 19-channel tubes. The residual of NaA zeolite was introduced into the silicon carbide (SiC) matrix, and porous SiC membrane supports were successfully prepared at 1100 °C. Compared with the disk-like support, the open porosity, average pore size and pure water permeance of the single-channel supports obviously increased, and their bending strength decreased accordingly. These differences were mainly attributed to the incorporation of organic plasticizer and the change in molding process. Notably, the pure water permeance of disks, single- and 19-channel tubes was 70 ± 3, 74 ± 4 and 22 ± 1 m3·m−2·h−1·bar−1, respectively, which was much higher than the previously reported values. Therefore, this work provides important guides to develop of new generation ceramic membranes for practical application.

Removal of acetaldehyde form indoor air using NaA zeolite and Modernite

Removal of acetaldehyde form indoor air using NaA zeolite and Modernite

A Coupling Process of Distillation with Vapor Permeation and Adsorption for Production of Fuel Ethanol: A Comparative Analysis on Energy Consumption

To efficiently produce fuel ethanol from fermentation broth, the distillation column was coupled with vapor permeation (VP) of a NaA zeolite membrane instead of using the adsorption technique to remove solvent water. The comparative analysis indicated that the energy efficiency was consistently higher for distillation-VP coupling, using a single-column distillation and three-column distillation, respectively. The best performance was obtained for the VP membrane coupling with a three-column distillation technique, where only 2.7 tons of steam per ton of fuel ethanol were consumed to produce fuel ethanol using a 3.0 wt % ethanol broth. This saved 0.25 tons of steam per ton of fuel ethanol in comparison with the results for the coupling with adsorption technique. The effect of ethanol content in broth on the energy efficiency was also investigated, which indicated that the ethanol content was a decisive factor to determine the energy consumption in the coupling techniques. The operation pressures were crucial to balance the energy consumption between columns coupled with the VP membrane. It was found that the operation pressure of the low-pressure column was the decisive factor to the whole energy efficiency, while the pressure of the high-pressure column was preferably adjusted according to practical production due to fewer disturbances in the system. This work benefits the process design for production of fuel ethanol from fermentation broth.

Synthesis of Novel CuO/ZnFe2O4/NaA Zeolite Nanocomposite Adsorbent for the Decontamination of Nerve Agent Sarin Simulant

The aim of present research is to evaluate the decontamination of nerve agent sarin simulant dimethyl methyl phosphonate (DMMP) in water media using the CuO/ZnFe2 O4 /NaA zeolite as a novel ternary nanocomposite adsorbent. In this regard, the CuO and ZnFe2 O4 nanoparticles were successfully synthesized within the NaA zeolite applying the ultrasound-assisted hydrothermal route and characterized via XRD, FESEM, FTIR, EDAX, VSM and BET analyses. Then, the CuO/ZnFe2 O4 /NaA nanocomposite activity was investigated for the decontamination of DMMP molecule and monitored by a GC-FID and GC-MS analyses. Plus, the impacts of several parameters, including contact time, adsorbent dose and adsorbent type on the decontamination of DMMP were studied. The gained data from GC-FID analysis confirmed the maximum decontamination more than 98.4% for DMMP. The parameters including: adsorbent amount of 50 mg and contact time of 40 min were achieved as the optimized values for the decontamination reaction. In addition, the non-toxic methyl phosphoric acid (MPA) as the DMMP degradation product in the presence of CuO/ZnFe2 O4 /NaA adsorbent was characterized.

Adsorption behavior and mechanism of mixed heavy metal ions by zeolite adsorbent prepared from lithium leach residue

Zeolite NaA was prepared from lithium leach residue (LLR) via the traditional hydrothermal synthesis method. The adsorption characteristics of zeolite on Pb 2+ and Cd 2+ were lucubrated to solve the problems caused by heavy metal wastewater and industrial waste LLR. The influence factors in the synthesis process were systematically explored. The cubic zeolite NaA was synthesized at 100 °C for 12 h when n(SiO 2 )/n(Al 2 O 3 ) was 2 and the alkalinity was 60 g/L. The performance of zeolite NaA to adsorb Pb 2+ and Cd 2+ in the mixed solution was also assessed in detail. Results showed that zeolite NaA had excellent adsorption property for Pb 2+ and Cd 2+ , and the maximum adsorption capacities of Pb 2+ and Cd 2+ were 487.805 and 193.798 mg/g. Moreover, the initial pH value of the solution and the adsorbent dosage greatly influenced the removal rates of Pb 2+ and Cd 2+ . The isotherm and kinetic analysis of the adsorption process revealed that Langmuir model and pseudo-second-order model agreed well with the adsorption process. The adsorption mechanism was accredited to the ion exchange and hydroxyl groups on the zeolite NaA surface. This work provided a rational process route of synthesizing zeolite NaA adsorbent from LLR, and it was well applied to the removal of Pb 2+ and Cd 2+ . • Zeolite NaA was synthesized from lithium leach residue. • The isotherm and kinetics of adsorption process were studied. • The maximum adsorption capacities of Pb 2+ and Cd 2+ were 487.805 and 193.798 mg/g. • The adsorption mechanism was accredited to the ion exchange and hydroxyl groups.

CO2 adsorption performance of template free zeolite A and X synthesized from rice husk ash as silicon source.

In this work, zeolite NaA (RA) and NaX (RX) have been successfully synthesized using rice husk ash and it is a low cost synthesis process and it does not produce environmental hazards. Sodium silicate (SS) is extracted from rice husk ash which is an alternative silica source for zeolite synthesis. The zeolites are prepared by using a SS silica source extracted from the rice husk ash, and it has been used as an adsorbent for the CO2 adsorption process which may help in controlling the global warming problems. The zeolites are synthesized by a hydrothermal method without using any organic templating agent. FESEM and TEM micrographs revealed that the synthesized zeolites RA and RX have “Ice cube” and octahedral morphology respectively. From the N2 sorption studies, the BET surface area of the synthesized zeolites have been found and are 106.25 m2 g−1 and 512.79 m2 g−1 respectively. The maximum CO2 adsorption capacities of zeolite RA and RX are 2.22 and 2.45 mmol g−1, respectively at a temperature of 297.15 K. The recorded data are fitted by using non-linear adsorption isotherm models of Langmuir, Freundlich and Toth isotherm models. The fitted isotherm models are observed to be a type I adsorption isotherm according to the IUPAC classification criterion.