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![Schematic of hydrothermal synthesis of zeolite [53].](publication/342457746/figure/fig4/AS:906480236642307@1593133138547/Schematic-of-hydrothermal-synthesis-of-zeolite-53.png)
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![Figure 1. Tetrahedral arrangement of the SiO 4 and AlO 4 molecules [28].](publication/342457746/figure/fig1/AS:906480236642306@1593133138442/Tetrahedral-arrangement-of-the-SiO-4-and-AlO-4-molecules-28_Q320.jpg)
![Figure 4. Schematic of hydrothermal synthesis of zeolite [53].](publication/342457746/figure/fig4/AS:906480236642307@1593133138547/Schematic-of-hydrothermal-synthesis-of-zeolite-53_Q320.jpg)
The development of Faujasite (FAU) zeolite membranes has been a subject of interest for various application due to the uniform pore’s characteristic, excellent thermal, and chemical stability as well as catalytic and ion-exchange properties of FAU zeolite membranes. However, the synthesis of FAU zeolite membranes with minimum defects is still chall...
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... the hydrothermal reaction in the presence of a "mineralizing" agent which is commonly an alkali metal hydroxide, the crystalline zeolite product containing Si-O-Al linkages is created [53]. The schematic of hydrothermal synthesis is illustrated in Figure 4. The most commonly studied zeolite membranes are supported zeolite membrane where membrane layer is synthesized on a porous support which can be from various materials such as alumina, glass, stainless steel, quartz, silicon carbide, mullite, zirconia, and titania [1,4]. ...
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... Despite the distribution in nature of such zeolites as clinoptilolite, mordenite, and Chabazite [25,26] synthetic zeolites of types A, X, Y and NaP1 are of particular value for industrial applications. [27][28][29]. The global synthetic zeolites market is segmented into three major production products: catalyst components, adsorbents and synthetic detergents. ...
Resource saving and creation of environmentally safe environment are the guidelines of modern world policy in the field of waste management. This paper considers a possible method of utilization of a by-product of aluminum fluoride production—silica gel—as an alternative high-silica raw material for hydrothermal synthesis of LTA-type zeolites. To obtain synthetic zeolites, industrial silica gel was subjected to sulfuric acid purification and used to obtain one of the hydrogel components—sodium silicate. As a result of investigation of the influence of hydrogel molar composition on the phase composition of the obtained samples, the optimal molar ratios of SiO2:Al2O3, Na2O:Al2O3 and H2O:SiO2 were identified. The phase composition of the obtained samples and morphological pattern were evaluated using X-ray diffraction and scanning electron microscopy techniques. According to the obtained results, the use of hydrogel of composition 1.8SiO2:Al2O3:4Na2O:28H2O allows to obtain a monophase of LTA type zeolite with high ion exchange capacity, the particles of which have a regular cubic shape with the size of the main fraction up to 10 μm.
... The second widely used strategy for FAU membrane synthesis is secondary growth. Secondary growth includes depositing seed crystals on the support surface via rub coating, dip coating, or vacuum suction, followed by secondary hydrothermal synthesis [21]. Secondary growth has many advantages compared to in situ crystallization methods. ...
... The preparation of zeolite membranes is affected by many factors, among which reasonable control of temperature and crystallization time is crucial for the preparation of pure FAU zeolite membranes and the avoidance of the formation of impurity phases. In this study, FAU membranes were prepared by hydrothermal synthesis at 358-378 K for 3-10 h by immersing the seeded supports in an ultra-dilute solution with a molar composition of 80Na 2 O: 1Al 2 O 3 : 19SiO 2 : 5000H 2 O. Compared with previous reports [19,23,29], the dilute clear reaction solution had a high water content, which plausibly reduced the nucleation effect in the bulk of the reaction solution and instead promoted crystal growth on the seed layer [21,30]. Figure 4 shows the XRD patterns of FAU membranes synthesized at 368 K for 3-10 h. ...
... Crystallization temperature is an important parameter for forming a specific type of zeolite phase. The hydrothermal synthesis temperature affects the nucleation and crystallization of zeolites, with higher synthesis temperatures leading to higher energy, which is beneficial to the crystallization process [21]. Figures 6 and 7 show the XRD patterns and SEM images, respectively, of the membranes synthesized for 8 h at different temperatures. ...
In this study, high-performance FAU (NaY type) zeolite membranes were successfully synthesized using small-sized seeds of 50 nm, and their gas separation performance was systematically evaluated. Employing nano-sized NaY seeds and an ultra-dilute reaction solution with a molar composition of 80 Na2O: 1Al2O3: 19 SiO2: 5000H2O, the effects of synthesis temperature, crystallization time, and porous support (α-Al2O3 or mullite) on the formation of FAU membranes were investigated. The results illustrated that further extending the crystallization time or increasing the synthesis temperature led to the formation of a NaP impurity phase on the FAU membrane layer. The most promising FAU membrane with a thickness of 2.7 µm was synthesized on an α-Al2O3 support at 368 K for 8 h and had good reproducibility. The H2 permeance of the membrane was as high as 5.34 × 10−7 mol/(m2 s Pa), and the H2/C3H8 and H2/i-C4H10 selectivities were 183 and 315, respectively. The C3H6/C3H8 selectivity of the membrane was as high as 46, with a remarkably high C3H6 permeance of 1.35 × 10−7 mol/(m2 s Pa). The excellent separation performance of the membrane is mainly attributed to the thin, defect-free membrane layer and the relatively wide pore size (0.74 nm).
... The second widely used strategy for FAU membrane synthesis is secondary growth. The secondary growth includes depositing seed crystals on the support surface via rub coating, dip coating, or vacuum suction, followed by secondary hydrothermal synthesis [21]. The secondary growth has many advantages compared to in-situ crystallization methods. ...
... In this study, FAU membranes were prepared by hydrothermal synthesis at 358-378 K for 3-10 h by immersing the seeded supports in an ultra-dilute solution with a molar composition of 80Na2O: 1Al2O3: 19SiO2: 5000H2O. Compared with previous reports [19,23,29], the dilute clear reaction solution had a high water content, which plausibly reduced the nucleation effect in the bulk of the reaction solution and instead promoted crystal growth on the seed layer [21,30]. Figure 4 shows the XRD patterns of FAU membranes synthesized at 368 K for 3-10 h. ...
... Crystallization temperature is an important parameter for forming a specific type of zeolite phase. The hydrothermal synthesis temperature affects the nucleation and crystallization of zeolites, with higher synthesis temperatures leading to higher energy, which is beneficial to the crystallization process [21]. Figures 6 and 7 show the XRD patterns and SEM images of the membranes synthesized at different temperatures for 8 h, respectively. ...
In this study, high-performance FAU (NaY type) zeolite membranes were successfully synthesized using small-sized seeds of 50 nm, and their gas separation performance was systematically evaluated. Employing nano-sized NaY seeds and an ultra-dilute reaction solution with a molar composition of 80 Na2O: 1Al2O3: 19 SiO2: 5000H2O, the effects of synthesis temperature, crystallization time, and porous support (α-Al2O3 or mullite) on the formation of FAU membranes were investigated. The results illustrated that further extending the crystallization time or increasing the synthesis temperature led to the formation of a NaP impurity phase on the FAU membrane layer. The most promising FAU membrane with a thickness of 2.7 µm was synthesized on an α-Al2O3 support at 368 K for 8 h, and had good reproducibility. The H2 permeance of the membrane was as high as 5.34×10-7 mol/(m2 s Pa), and the H2/C3H8 and H2/i-C4H10 selectivities were 183 and 315, respectively. The C3H6/C3H8 selectivity of the membrane was as high as 46 with a remarkably high C3H6 permeance of 1.35× 10-7 mol/(m2 s Pa). The excellent separation performance of the membrane is mainly attributed to the thin, defect-free membrane layer and relatively wide pore size (0.74 nm).
... Schematic diagram for hydrothermal synthesis of zeolite membranes[264]. ...
Clean methanol can play an important role in achieving net zero emission targets by decarbonizing the energy and chemical sectors. Conventionally, methanol is produced by using fossil fuel as raw material, which releases a significant amount of greenhouse gases (GHGs) into the environment. Clean methanol, which is produced by hydrogen (H2) from renewable sources (green H2) and captured carbon dioxide (CO2), is totally free from the influence of fossil fuel. Due to its vast applications, clean methanol has potential to substitute for fossil fuels while preventing further GHGs emissions. This review addresses the feasibility of producing clean methanol from renewable resources, i.e., green H2 and captured CO2. Availability of these raw materials is the main factor involved in establishing the circular economy of methanol, therefore, their potential sources and the possible pathways to access these sources are also summarized. Renewable energy sources such as solar, wind and biomass should be utilized for producing green H2, while CO2 captured from air, and more likely from point emission sources, can be recycled to produce clean methanol. After producing methanol from CO2 and H2, the removal of by-product water by distillation is a big challenge due its high energy consumption. An alternative approach for this methanol-water separation is membrane technology, which is an energy saving option. Water-selective zeolite membranes can separate water post-synthesis, as well as during the synthesis. Production efficiency of methanol can be enhanced by utilizing zeolite membranes inside the methanol synthesis reactor. Furthermore, CO2 conversion as well as methanol selectivity, purity and yield can also be increased significantly by selectively removing by-product water using a zeolite membrane reactor.
... The mechanism of molecular sieve points that the membrane pore size among different molecules, allowing smaller molecules to selectively travel through the membrane over larger molecules for separation. Molecular sieving is commonly employed to describe gas molecule diffusion in inorganic membranes, like zeolites membrane [29] and CMS membranes [30]. The other two mechanisms are typically applied to polymer membranes [27,28]. ...
Membrane separation technology provides an effective alternative to mitigate the massive carbon emission with high carbon capture productivity and efficiency. In the context of operating membranes under high CO2 pressures allows increased separation productivity and reduced gas compression cost, which, however, often leads to CO2 induced plasticization, a key hurdle for current gas separation membranes. In this review, we reviewed the latest development of membranes with anti-plasticization resistance, potentially suited for operation under high CO2 feed streams. Specifically, the separation performance of polymeric membranes, inorganic membranes, and mixed matrix membranes under high CO2 feed pressures are discussed. Approaches to enhance CO2 induced plasticization of those membranes are also summarized. We conclude the recent progress of membranes for high CO2 pressures with perspectives and an outlook for future development.
... . Pada struktur kerangka zeolit terdapat rongga antar kristal yang ditempati oleh kation dan molekul air yang sifatnya mudah terlepas saat mengalami pemanasan. Ketika molekul air dihilangkan, pori mikro dan rongga akan melebar dan dapat membentuk 50% dari volume kristal [4]. Sruktur rongga yang saling berhubungan ke segala arah meneyebabkan permukaan zeolit menjadi luas serta kemampuan dalam menukar kation yang tinggi membuat zeolit menjadi salah satu alternatif adsorben dengan kemampuan adsorbsi yang baik. ...
Natural zeolite is one of the alternative adsorbents with good absorption capabilities, including in absorbing color. The adsorption ability of zeolite can be increased by the activation process because it can increase the Si/Al ratio and pore size. Dragon fruit peel is a natural material that can be used as a natural dye because it contains betacyanin pigments which are equivalent to synthetic dyes. This study aimed to investigate the characteristics of activated green and brown zeolite and their adsorption ability on natural dyes of dragon fruit peel. Zeolite was activated chemically using 3M HCl solution and physically through a heating process of 500°C, then characterized using XRD and FTIR. The zeolite adsorption process was carried out with variations in contact time of 30, 60 and 90 minutes and variations in the mass of the adsorbent 0.1, 0.3 and 0.5 grams. The results of XRD analysis showed that the green and brown zeolite contained mordenite, nepheline and quartz minerals. The highest percentage of color degradation in the adsorption process was in brown zeolite at 27.70% at a contact time of 90 minutes and 88.2% at an adsorbent mass of 0.5 grams. Differences in brown zeolite before and after adsorption can be seen from the shift in the wavelength of each functional group due to the interaction with dragon fruit peel.
... The d6rs are arranged as the carbon atoms in the diamond crystal structure and generate a large open framework, characterized by a very low framework density (12.7 T-atoms per 1000 A 3 ), with a large "supercage" [41864124] accessible through circular 12-ring apertures (7.4 ×7.4 Å) ( Fig. 1) [64]. FAU-type zeolites, such as zeolite Y, have high thermal stability, a large void volume (~50%), and find application in several technologies including cracking catalyst [71,72], membrane separation [73][74][75], water purification [76,77] and pervaporation [78,79]. ...
The adsorption efficiency of Zeolites Y (FAU-type topology) with different silica/alumina ratio towards perfluorooctanoic acid (PFOA, C8HF15O2) and perfluorooctane sulfonate (PFOS, C8F17SO3H), was investigated by combining batch adsorption and synchrotron X-ray powder diffraction (XRPD) analyses. Adsorption isotherms show that the saturation capacity of Y390 as-synthesized and Ag-exchanged sample, was for PFOA was ~43% and ~62%, and for PFOS was ~17% and ~32% in weight respectively. XRPD Rietveld refinements provided the exact location of PFOA and PFOS in the zeolites network before and after functionalization with Ag. PFAS are located at the center of the supercage, H- bonded to both co-adsorbed water molecules and framework oxygen atoms. Y-PFOA/PFOS and AgY-PFOA/PFOS oligomers strongly interact with oxygen atoms of the zeolite framework, thus immobilizing the pollutants in the zeolite microporosity. These findings indicated that these materials can be successfully used for the decontamination of water from perfluoroalkyl chemicals. Additionally, introduction of Ag onto zeolites could confer combined antifouling and adsorption properties thus exhibiting improved performances compared to zeolite as single compounds thus working synergistically in removal of PFAS from water.
... The synthesis of zeolites involves several steps, according to Davis and Lobo [29]: nucleation, aggregation, crystallization, and growth [30,31]. De Moor investigated the perception of the initial process of zeolites using techniques for in situ characterization in 1998 [30,31]. ...
... The synthesis of zeolites involves several steps, according to Davis and Lobo [29]: nucleation, aggregation, crystallization, and growth [30,31]. De Moor investigated the perception of the initial process of zeolites using techniques for in situ characterization in 1998 [30,31]. Two theories of zeolite synthesis exist the solid-solid transformation (nucleation process) and (ii) the mechanism of crystallization [32]. ...
Zeolite A was successfully synthesized using Perak kaolin which acts as the main source of silica and alumina. The process of beneficiation was conducted on raw kaolin to remove the impurities that existed in natural kaolin and also to increase the physical and chemical characteristic of kaolin. The kaolin was continued to be heated in the furnace with the temperature of 600⁰C for 4 h which described as a metakaolinization process that transformed it into the amorphous stage. The raw kaolin was characterized by XRD, FESEM, FTIR, PSA, TGA, while metakaolin by XRD, FESEM and FTIR. The mixture of zeolite A was achieved by adding the metakaolin into sodium hydroxide (NaOH) solution without adding other sources of silica and alumina. The solution mixture was stirred for 24 h before undergoing the process of hydrothermal synthesis. Two optimum conditions were studied for Zeolite A synthesizing, which were different molarity of sodium hydroxide and crystallizations time during the hydrothermal process. The successful synthesis of Zeolite A was then characterized by XRD, FESEM, FTIR, PSA, and BET surface area. The BET surface area of Zeolite-A is higher, 5.26 m²/g, compared to natural zeolite, 2.9 m²/g. As demonstrated in this work, Perak kaolin which was successfully synthesized into Zeolite-A with 2 M NaOH and 12-h crystallization time, gave a higher crystallinity percentage, 72.97%. The results obtained revealed that formation The of zeolite A has been highly affected by the NaOH molarity and crystallization time used in the combination of reactions.
... MMMs consist of inorganic and polymeric phases [9] and they are typically prepared by casting a solution of polymer and dispersed inorganic phase, and then evaporating the solvent in a controlled environment to obtain a dense membrane. The polymeric phase is usually the bulk phase while the inorganic particle phase comprises the dispersed phase in the form of active fillers such as porous organic molecular cages (POMC) [10], zeolites [11], graphene-based materials [12], and metal organic frameworks (MOFs) [13]. Due to inherent superior separation characteristics of inorganic particle phase, mixed matrix membrane gives high permeability and permselectivity as compared to only polymeric phase membrane. ...
Membrane separation has been an efficient and energy saving technique in dealing with greenhouse gases, but the traditional membrane designs might not be able to handle the concomitant environmental pollution due to their fixed properties. Correspondingly, the use of an active-responsive smart membrane appears to be a new trend for membrane development in the coming future, which shows great potential to deal with the obstacles. In this research, we demonstrate a smart graphene-organic framework membrane to enable reversed electrical-switchable permselectivity in CO2 separation. The addition of polydopamine (PDA) to the polyvinylidene fluoride/Graphene (PVDF/G) membranes was done to (i) induce the β-phase of PVDF, since −NH2-functionalized graphene has specific interactions (dipole induced dipole interaction) between graphene-PDA and PVDF; (ii) modify the organic PVDF-inorganic graphene interface; and (iii) facilitate CO2 selective separation. Permeability and permselectivity was increased after applying voltage that resulted in the increase of gas permselectivity in response to the lowest applied voltage range (0-3 V) to the membrane. Digital image correlation method depicted the response of the membrane to voltage and proved that the membrane has high piezoelectric properties that is switchable. Furthermore, PALS studies confirmed the free volume and interlayers in the membrane. This membrane has unique properties because the pore changes from bimodal to single pore distribution.
... Zeolit-X dikarakterisasi menggunakan Fourier Transform Infrared (FTIR) untuk mengetahui gugus Si-Al pada zeolit-X. Gambar 6 menunjukkan puncak-puncak yang muncul mengindikasikan beberapa gugus fungsi 3340,17 cm -1 merupakan vibrasi ulur dari gugus OH yang menunjukkan adanya air dalam sampel dan diperkuat oleh puncak pada 1636,83 cm -1 yang timbul akibat vibrasi tekuk gugus -OH [24]. ...
