Zeolite Products Research Articles

A Noble and Economical Method for the Synthesis of Low Cost Zeolites From Coal Fly Ash Waste

ABSTRACT Coal fly ash (CFA) is one of the major global pollutants, which is continuously invading a huge amount of land every year; consequently, there is depletion of barren land. Even, in the 21st century, a hundred per cent utilisation of fly ash is not achieved. Here, in the present research work, fly ash is processed initially with the mineral acids followed by the alkali treatment under optimised conditions. The alkali treatment of fly ash revealed the formation of geopolymers like the structure of variable shapes and sizes. The confirmation and identification of the final desilicated product were done by infrared spectroscopy i.e. (FT-IR), X-ray diffraction (XRD), X-Ray fluorescence (XRF), Field Emission Scanning Electron Microscopy (FESEM-EDS) and Transmission Electron Microscopy (TEM). The size of the zeolitic product was varying from 60 to 120 nm in width and 80 to 700 nm in length. While the shape of the particles was varying from spherical to needle and rod-shaped. The current method suggested the transformation of fly ash waste into the zeolite product. The synthesis of such particles from fly ash makes the process and product economical and eco-friendly by providing a safe and environment-friendly disposal of fly ash.

Diverse zeolites derived from a circulating fluidized bed fly ash based geopolymer for the adsorption of lead ions from wastewater

The transformation of geopolymers into zeolite materials for use as bulk-type adsorbents is an outstanding strategy for water pollution control. However, only sodium ion (Na+)-type zeolites can be typically obtained from geopolymers, which limits their variety. In this study, Li-ABW zeolite (Li-ABW), K–F zeolite (K–F), and phillipsite, were obtained via the hydrothermal transformation of a circulating fluidized bed fly ash (CFBFA)-based geopolymer using single alkali metal cations of either lithium (Li+) or potassium (K+), as well as coexisting Na+ and K+ as structure-directing agents. X-ray diffractometry and field emission scanning electron microscopy indicate that the amorphous CFBFA-based geopolymer was converted into well-defined Li-ABW zeolite, K–F zeolite, and phillipsite. The obtained zeolite products were subsequently employed as adsorbents to remove lead ions (Pb2+) from the aqueous solution, leading to adsorption capacities of 160.70, 239.50 and 252.70 mg/g for Li-ABW, K–F, and phillipsite, respectively. The kinetics of Pb2+ adsorption on the three zeolite samples fit the pseudo-second order model well, suggesting that Pb2+ adsorption on the zeolite samples occurs via chemical adsorption. The adsorption isotherms followed the Langmuir model, thereby confirming monolayer adsorption of Pb2+ on the as-synthesized zeolites. The combined results indicate that the zeolites derived from the CFBFA-based geopolymers are appropriate for Pb2+ removal from wastewater. This work provides new insights for the use of CFBFA industrial waste and the development of geopolymer-based adsorbents for the sustainable development of wastewater treatment methods.

East Transbaikal zeolite production: Potential and integrated Ecological safety

The author discusses resource potential of zeolite-bearing rocks in East Transbaikal with regard to geoecological safety of mining and processing. The role of climate in the environmental impact of zeolite production is identified. Potential activities aimed to reduce anthropogenic load on the environment are proposed.

The development of technology for production of zeolites from fly-ash from Troitskaya power plant

The study examines the technology of processing fly ash from Troitskaya power plant for the production of zeolite. The paper presents the results of laboratory studies evaluating the suitability of fly ash from Troitskaya power plant for the production of zeolites and the development of the zeolite production process. Fly ash contains a small amount of heavy metals that can complicate processing, but contains a large amount of silicon oxide. The technology consists of high-temperature alkaline activation of fly ash and hydrochemical synthesis. The resulting powder has a specific surface area of 89.7 m2/g, determined by the BET method, and an average pore diameter of 0.345 μm. The static exchange capacity was 220 mg/g.

An ambient pressure method for synthesizing NaY zeolite

Abstract Zeolites are vital industrial materials applied widely in the field of heterogeneous catalysis. Porous zeolites are essentially synthesized in the presence of soft or hard templates in processes such as hydrothermal, solvothermal, and ionothermal synthesis. Herein, we demonstrated a facile ambient pressure technique to synthesize NaY zeolite using a glass tube as a reactor and a fluid sealant to create a physical barrier between the reactor contents and the atmosphere. The synthesized zeolite Y was characterized by XRD, SEM, TEM, UV-Raman, N2 sorption, MAS NMR, and XRF spectroscopy. In comparison to the traditional hydrothermal synthesis routes, the avoidance of high-pressure synthesis apparatus not only reduces safety risks but also significantly improves the yield of zeolite products with a crystallinity of 52% and Si/Al = 3.51. Furthermore, the process is leaner, efficient, and reduces costs. Optimum conditions realized for the synthesis of highly crystalline zeolite Y were 90 °C and 18 h crystallization temperature and period respectively, using 1-dodecanol as a sealant. Subsequently, PEG6000 emerged the best among organic templates investigated to improve porosity while maintaining high crystallinity of the zeolite.

Study on the Synthesis of Chabazite Zeolites via Interzeolite Conversion of Faujasites.

The interzeolite conversion of faujasite (FAU-type) zeolites to chabazite (CHA-type) zeolite in the presence of N,N,N-trimethyladamantammonium and N,N,N-dimethylethylcyclohexylammonium cations was investigated over a large compositional range by carefully controlling the reaction mixture compositions. Highly crystalline CHA zeolites were also obtained by the transformation of several zeolite types including EMT, LTL, LEV, RTH, and MFI frameworks. The formation of CHA zeolite from FAU zeolite precursors was substantially faster than that from zeolite L with a similar composition. High-silica CHA zeolites were also produced successfully using a mixture of TMAda with a number of less expensive organic structure-directing agents. The CHA zeolite materials have been synthesized with high crystallinity and with a Si/Al ratio ranging from 5 to 140. Our data support the importance of structural similarity between the zeolite precursors, nucleation/crystallization processes, and the zeolite product in the interzeolite conversion compared to conventional amorphous aluminosilicate gels. Our synthetic methods could be used to prepare other 8-membered ring zeolites such as AEI and AFX frameworks, potential candidates for selective catalytic reduction of NOx, light olefin production, and CO2 abatement.

Microporous and macroporous materials state-of-the-art of the technologies in zeolitization of aluminosilicate bearing residues from mining and metallurgical industries: A comprehensive review

For decades, the world has experienced a steadily increasing demand in the extraction of a variety of different minerals from the earth's crust through mining processes. This has resulted in two major consequences: i) depletion of limited mineral resources of the earth, and ii) generation of large amounts of residual products in the mining and metallurgical sectors, that are disposed of in tailing ponds or landfill sites. These issues have caused that the world is encountering with incredibly serious economic and environmental challenges. Reuse, repurposing and valorization of these residues have been determined as effective and sustainable approaches towards struggling with economic and environmental issues related to the exploitation of low-grade deposits. These residues are divided into several categories according to their chemical and mineralogical compositions, since these parameters play essential roles in their repurposing/valorization. Among these residues, aluminosilicate bearing residues have demonstrated promising potential as inexpensive raw resources to produce valuable materials. In the recent years, these residues have been intensively investigated for their use in the production of cost-effective zeolites, which are crucial materials for catalysis and adsorption–separation industries. This alternative in zeolite production is of continuous interest in the field of zeolite science due to: i) important reduction in zeolite production costs, ii) sustainable development concepts as well as iii) helping to tackle the environmental concerns related to long-term management of residues. Herein, the endeavor is to discuss about the state-of-the-art technologies for zeolitization of aluminosilicate bearing residues including coal fly ash, clay minerals residues, Li slag, Al production residues, with an emphasis on the ongoing struggles in improvement of their corresponding zeolitization processes. • Valorization of mining and metallurgical residues can result in sustainable development. • Aluminosilicate bearing residues can contain zeolite precursors. • Several synthesis procedures exist to produce zeolites form aluminosilicate residues. • Zeolitization of aluminosilicate residues is influenced by a wide range of parameters. • More researches on technology development, process optimization as well as economic assessment are still needed.

Methanol‐to‐Olefins Reaction over Large‐Pore Zeolites: Impact of Pore Structure on Catalytic Performance

AbstractIn the methanol‐to‐olefins (MTO) reaction, product flexibility is important for meeting the fluctuating chemicals demands. In this paper, the catalytic performance of recently reported zeolites having 12‐ring pores, such as boroaluminosilicate CON‐type zeolite ([Al,B]‐CON), MCM‐68, and YNU‐5 zeolites, in the MTO reaction was compared to understand the relationship between zeolite framework and product selectivity. The catalytic performance of the synthesized zeolites was compared with that of Beta, mordenite, and ZSM‐5. The highest selectivities for propylene and butylenes were achieved over MCM‐68. The highest propylene‐to‐ethylene ratio in the products was obtained over [Al,B]‐CON. ZSM‐5 and [Al,B]‐CON exhibited a superior ability to suppress coke formation compared to Beta, mordenite, MCM‐68, and YNU‐5.

A facile approach for construction of hierarchical zeolites via kinetics

Abstract It has long been a dream to construct hierarchical zeolites by a really simple and cost-effective method which is feasible in industry. Here we provide an alternative approach in which the crystallization kinetics is regulated by solely changing the added amount of NaOH in the initial gel of a traditional zeolite and then the adjustment of the morphology and structure of the zeolite products is realized. This approach overcomes most of the limitations associated with the popular methods, such as complex operations and costly secondary templates. As an example, hierarchical ZSM-5 zeolite is prepared with using the most common raw materials and synthesis technology which used in the large-scale production of traditional zeolites. The crystallization process of the hierarchical ZSM-5 zeolite is investigated in detail and compared with the microporous zeolite. The results indicate that the increase of NaOH concentration in the synthesis system can enhance the rate of nucleation but the hierarchical pore structure can be formed only under the moderate concentration. The crystallization of the hierarchical ZSM-5 zeolite takes place by a chain of processes: (i) formation of wormlike precursors, (ii) aggregation of the precursors, (iii) condensation of the precursors and formation of internal voids, (iv) formation of external shell layers. The performance studies show that the obtained hierarchical ZSM-5 zeolite possesses significantly enhanced diffusion property and superior ability for catalytic cracking bulky molecules.

Milling Activation for the Solvent-Free Synthesis of Zeolites. A Practical Guide

The paramount challenge of current chemical technology, including catalysis, is meeting the ecological sustainability requirements. The feasible production of zeolites is crucial because they constitute the principal group of heterogeneous catalysts. However, current zeolite manufacturing via hydrothermal synthesis is connected with considerable consumption of water resources, generation of wastewater, and significant equipment costs. Solvent-free strategies have attracted great attention as high-yielding methods for sustainable synthesis, particularly beneficial in terms of water consumption minimization and an outstanding increase in production due to the efficient use of synthesis space capacity. So far, the solvent-free preparation of numerous zeolite materials has been performed with the preceding grinding of reagents in a mortar. The proposed article describes recent advances in the application of automatized milling instead of manual work. Pretreatment automatization makes the entire process well-controlled, less sensitive to human factors, and is significantly more relevant to industrial scale-up. Moreover, the automatized milling activation unlocks opportunities for solvent-free synthesis from a broader range of common reagents, where the manual treatment is not efficient. Possibilities and limitations of the milling methods are discussed on the basis of a comprehensive analysis of parameter optimization, activation mechanisms, and applicability of common reagents used for zeolite production.

The Effect Of SiO2 / Al2O3 Ratio Over Yield And Particle Size In Zeolite from Geothermal Waste

Hydrogen is one of compound much used in the chemical industry. Production process of hydrogen commonly applied in the industry is steam reforming using high temperatures. Catalyst can be used in the production of hydrogen is zeolite. Zeolites are the result of mine nonmetallic, so the availability is limited. PT Geo Dipa energy unit Dieng produce industrial waste of deposition silica and it can be used as zeolite materials. The objective of this research for preparation of catalyst from solid waste of geothermal industry with varied ratio of SiO2/Al2O3. The geothermal waste was calcined at a temperature of 1000 °C. The waste geothermal was mixed with 400 ml of Sodium Hydroxide 3M and added with Aluminum Hydroxide at 100 °C for two hours. Hydrothermal process was conducted at 300°C for five hours. The calcination of zeolite products for five hours at 700 °C. This research concludes that washed catalyst has a smaller yield than native. The greater ratio of SiO2/Al2O3 gives smaller yield. Catalysts that are washed have smaller particle sizes than without washing. Larger ratio of SiO2/Al2O3, it produces smaller particle sizes. In the analysis using the Particle Size Analyzer method, the resulting particle size is still relatively large at a micro scale.

Anionic Tuning of Zeolite Crystallization

Zeolites are of great industrial relevance as catalysts, adsorbents, and ion-exchangers and typically synthesized under hydrothermal conditions. Rational regulation of their crystallization process...

Transformation of heulandite type natural zeolites into synthetic zeolite LTA

This study developed an approach to synthesise zeolite LTA from three different natural heulandite class zeolite deposits (Escott, Avoca, and NextSand). The challenge was to determine the impact of pre-activation of clinoptilolite or heulandite materials upon the synthesis of zeolite LTA. Heulandite (Escott; Avoca) was thermally less stable ( ca. 200 o C) than clinoptilolite (NextSand) ( ca. 600 o C); with all samples losing cation exchange capacity as a result of heating at elevated temperature ( ca. 120 to 30 meq/100 g). Attempts to synthesise zeolite LTA from as received natural zeolite under typical industry conditions (80 °C; 2 h) were not successful due to the stability of the natural zeolite framework. In agreement with this discovery, the amount of active alumina and silica was relatively small (<3.5 % for silica; <36.4 % for alumina). Alternatively, activation with either alkali fusion or a combination of heating and fusion at temperatures up to 800 °C typically resulted in formation of >80 % of monomeric silicates and aluminates. Significantly, the zeolite product resultant from hydrothermal synthesis of the activated materials comprised of ca. 85 % crystalline zeolite LTA and non-diffracting material; independent of the activation method or the identity of the natural zeolite. This study revealed that fusion activation of natural zeolites improved the robustness of the synthesis process and opened up new avenues for green zeolite formation. Future studies should focus on reducing the activation costs by lowering activation temperature and sodium hydroxide consumption. • Zeolite LTA synthesised from natural zeolites in a two-step process. • Thermal activation of natural zeolite inadequate to make zeolite LTA. • Alkali fusion required to depolymerise silica and alumina species. • Fusion conditions have relatively small impact on zeolite LTA quality. • Zeolite LTA production independent of natural zeolite identity.

SAPO-34 Obtained from Amazonian Flint Kaolin: Influence of Impurities ‘Oxidized Fe/Ti’ in the Synthesis and its Application in the Removal of Cationic Dye from Water

The non-processed kaolin (flint kaolin) from a mine located in the Capim area (Amazon region, northern Brazil) considered a waste was selected as a source of silicon and aluminum in the synthesis of SAPO-34, a molecular sieve and cationic exchanger chosen for tests in the removal of methylene blue in aqueous solution, which is a cationic dye widely used by textile industries in Brazil. The results revealed that the SAPO-34 has been successfully synthesized with typical cubic morphology, good crystallinity (> 90%) and thermal stability (~ 998 oC). And although the oxidized Fe/Ti impurities contained in the flint kaolin affects the degree of crystallinity of the zeolitic product, its adsorptive properties are not significantly affected, which showed the excellent adsorption results (pH = 11; % removal > 90%), which proved to be an adsorbent with considerable adsorption capacity (9.83 mg.g-1). The pH test confirmed the acidic surface characteristic (pH solution 2 - 4; ↓ removal) and the kinetic model that best fitted the experimental data was the pseudo-second-order with R2 = 0.998 (kinetics controlled by chemisorption).

Quasi Natural Approach for Crystallization of Zeolites from Different Fly Ashes and Their Application as Adsorbent Media for Malachite Green Removal from Polluted Waters

Worldwide disposal of multi-tonnage solid waste from coal-burning thermal power plants (TPPs) creates serious environmental and economic problems, which necessitate the recovery of industrial waste in large quantities and at commercial prices. Fly ashes (FAs) and slag from seven Bulgarian TPPs have been successfully converted into valuable zeolite-like composites with various applications, including as adsorbents for capturing CO2 from gases and for removal of contaminants from water. The starting materials generated from different types of coal are characterized by a wide range of SiO2/Al2O3 ratio, heterogeneous structure and a complex chemical composition. The applied synthesis procedure resembles the formation of natural zeolites, as the raw FAs undergo long-term self-crystallization in an alkaline aqueous solution at ambient temperature. The phase and chemical composition, morphology and N2 adsorption of the final zeolite products were studied by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-Ray Diffraction (XRD) and Brunauer–Emmett–Teller (BET) analyses. The growth of faujasite (FAU) crystals as the main zeolite phase was established in all samples after 7 and 14 months of alkaline treatment. Phillipsite (PHI) crystals were also observed in several samples as an accompanying phase. The final products possess specific surface area over 400 m2/g. The relationships between the surface properties of the investigated samples and the characteristics of the raw FAs were discussed. All of the obtained zeolite-like composites were able to remove the highly toxic dye (malachite green, MG) from water solutions with efficiency over 96%. The experimental data were fitted with high correlation to the second-order kinetics.

Investigation of ZSM-12 nanocrystals evolution derived from aluminosilicate nanobeads for sustainable production of ethyl levulinate from levulinic acid esterification with ethanol

Abstract The evolution of hierarchical ZSM-12 nanosized crystals as a function of crystallization time has been demonstrated using amorphous aluminosilicate (AS) nanobeads as simultaneous silica and alumina sources and cyclic diquaternary ammonium as a structure-directing agent (SDA) in a one-pot hydrothermal synthesis. The physicochemical properties of the derived ZSM-12 products were characterized by means of X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) elemental analysis, N2 physisorption, temperature-programmed desorption of ammonia (NH3-TPD), and pyridine adsorption. It is clearly demonstrated that crystallinity, textural properties, and acidity of the zeolite products are enhanced as a function of crystallization time. The structure of nanocrystalline ZSM-12 is well-developed after 120 h of crystallization and the corresponding zeolite product exhibits the promising catalytic performance for sustainable production of ethyl levulinate (EL) from levulinic acid (LA) esterification with ethanol. This contribution illustrates an alternative way to synthesize hierarchical zeolite nanocrystals with MTW framework via the use of homogeneously dispersed aluminosilicate nanobeads as the starting materials and opens up the perspectives for the sustainable application of zeolites nanosized crystals in a bulky-molecule reaction of bio-based chemical synthesis.

Utilization of wastewater from zeolite production in synthesis of flotation reagents

Abstract The application of waste alkali liquids as a substitute of sodium hydroxide for the saponification to improve the collection performance of fatty acids was investigated by saponification reaction test and flotation test. The results of the saponification reaction test indicated that the optimal conditions for the saponification were stirring rate of 55 r/min, initial temperature of 40 °C and stirring time of 45 min. Meanwhile, the laboratory scale and industrial scale flotation experiments showed that the fatty acid salt synthesized by wastewater achieved an index comparable to fatty acid sodium synthesized by sodium hydroxide. As a consequence, it was feasible to replace sodium hydroxide with the wastewater from zeolite production for fatty acid saponification. The cross-border utilization of waste alkali liquids not only reduced environmental pollution, but also produced excellent economic benefits.

Synthesis of sole gismondine-type zeolite from blast furnace slag during CO2 mineralization process

CO2 mineralization is one of the most important strategies for reduction of anthropogenic CO2 emissions. Preparation of high-value products during this process would improve its economy and make it more promising for industrial applications. In this study, sole gismondine-type zeolite (zeolite P) was synthesized during the CO2 mineralization process by using blast furnace slag as feedstock. The optimal experimental conditions and regression model for synthesis of zeolite was determined through Response surface methodology. The results showed that a well-crystallized zeolite was obtained with a short hydrothermal time at high temperature even at low alkalinity. However, too high temperature and alkalinity can promote the formation of sodalite, reducing the relative content of zeolite P in the product. Different analysis methods such as XRD, FTIR, SEM were applied to characterize the products and investigate the synthesis mechanism of zeolite formation. The analysis indicated that zeolite products with a uniform shape of octahedron can be obtained under mild conditions (NaOH concentration of 1.5 mol·L−1, 120 °C, 2∼4 h). The formation of zeolite from blast furnace slag can be divided into four steps, i.e., dissolution of aluminate ions and silicate ions from raw material, formation of the amorphous intermediate aluminosilicate gel precursor, rearrangement of the structure of aluminosilicate precursor to form nuclei of zeolite, and crystal growth. Based on the results in this study, major components of blast furnace slag were utilized fully (Mg and Ca for CO2 storage, whilst Al and Si for synthesis of zeolite), reducing the overall cost of CO2 mineralization.

Synthesis and characterization of NaX-type zeolites prepared by different silica and alumina sources and their CO2 adsorption properties

Abstract In this work, two pairs of silicon and aluminium sources (sodium silicate solution + Al(OH)3 and sodium silicate powder + sodium aluminate) were used for synthesizing zeolites which were labeled as Z1 and Z2, respectively. The results from XRD, BET and surface analysis indicated that sodium silicate and sodium aluminate sources yielded zeolite with high surface area and pore volume. Cetyltrimethylammonium bromide (CTAB) and heptane were used to modify the CO2 adsorption capacity and selectivity of zeolite NaX. The surface area and pore volume of zeolite products increased due to smaller crystalline size and then resulted in significant enhancement of CO2 uptake of the synthesized zeolite NaX. The role of additives on zeolite formation was to increase the nuclei formation rate and number which gave rise to smaller zeolite crystals. The best adsorbent exhibited high CO2 adsorption capacity (5.08 mmol g−1 at 303 K) and relatively high CO2 selectivity over N2 (116) which indicated the potential of adsorbent to separate CO2 from flue gas application.

Utilization of rice husk and waste aluminum cans for the synthesis of some nanosized zeolite, zeolite/zeolite, and geopolymer/zeolite products for the efficient removal of Co(II), Cu(II), and Zn(II) ions from aqueous media

In this paper, rice husk and waste aluminum cans were exploited as silicon and aluminum sources, respectively for the low-cost synthesis of some nanosized zeolite, zeolite/zeolite, and geopolymer/zeolite products. XRD confirmed that the synthesized geopolymer/zeolite products are geopolymer/zeolite A (has a crystallite size of 58.44 nm & abbreviated as G1) and geopolymer/faujasite (has a crystallite size of 25.58 and 20.26 nm & abbreviated as G2 and G3, respectively). Also, the synthesized zeolite products are sodium aluminum silicate hydrate (has a crystallite size of 27.65 and 41.85 nm & abbreviated as H1 and H2, respectively). Besides, the synthesized zeolite/zeolite product is sodium aluminum silicate hydrate/zeolite A (has a crystallite size of 66.01 nm and abbreviated as H3). Moreover, the synthesized products were characterized using other tools such as HR-TEM, FE-SEM, EDX, and FT-IR. The synthesized products were efficiently applied for removing Co(II), Cu(II), and Zn(II) ions from aqueous media and wastewater which was taken from Abuzaabal- Qalyubiyah-Egypt. The maximum uptake capacity of G3 sample toward Co(II), Cu(II), and Zn(II) ions is 134.24 ± 1.26, 126.26 ± 0.32, and 131.93 ± 0.87 mg/g, respectively. The uptake of the studied metal ions is spontaneous, chemical, exothermic, and fitted well with the Langmuir isotherm and pseudo-2nd-order kinetic model.