Seed-Assisted Crystallization in the Hydrothermal Synthesis of FAU Zeolite from Acid-Treated Residue Glass Powder

Sayehi M., Delahay G., Tounsi H.

In this study, we reported a simple and easy process for zeolite synthesis using waste glass and aluminum scraps. The silica source was obtained from glass of the end-of-life fluorescent tubes and aluminum source was scraps collected from aluminum workshop in the region of Sfax, Tunisia. The zeolitic materials were prepared by hydrothermal treatment at 60 °C for 6 days using 10 g of glass powder mixed with 100 mL sodium aluminate solution prepared from aluminum scraps. In order to optimize the nature of the recovered zeolites, reaction time, particle size, aluminum concentration and liquid/solid ratio were monitored. The starting materials and the prepared zeolites were characterized by X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Nuclear Magnetic Resonance (NMR) of 27Al and 29Si nuclei. The characterization techniques demonstrated that the recovered solid after 6 days of crystallization at 60 °C using different particle sizes (ø

Lee W., Lin Y., Lin K.

This paper examines the synthesis of zeolite A via hydrothermal alkali fusion using liquid crystal display waste glass (LCDWG) and sandblasting waste (SB). The design of the experiments was determined using the Box-Behnken method in conjunction with response surface design. Three factors were shown to have a pronounced effect on synthesis outcomes: (i) Si/Al molar ratio, (ii) crystallization temperature, and (iii) crystallization period. Synthesis parameters were optimized in accordance with the crystallinity (%) of the zeolite. XRD results revealed that increasing the Si/Al ratio improved the crystallinity and phase purity of the synthesized zeolite A. Increasing the crystallization temperature altered the crystal type and enhanced crystal purity; however, excessive temperatures reduced crystallinity and led to decomposition of the zeolite A phase. SEM results revealed that the resulting zeolite A possessed a cubic structure. ANOVA revealed that the Si/Al molar ratio had the most profound effect on the synthesis of zeolite A, followed by crystallization duration and crystallization temperature. The fact that the R 2 value (0.95) was similar to the adjusted R 2 value (0.8736) confirmed the efficacy of the proposed polynomial model. A highly significant F-value of 11.75 confirmed that the proposed model could be used for design purposes. The excellent water adsorption/desorption performance of the proposed zeolite A (49.83 g/ m 2 ; meeting JIS A 1470 standards) indicates its suitability as a low-cost construction material for a variety of applications. The ultimate objective of this study was to overcome difficulties encountered in the disposal of industrial waste by converting LCDWG and SB into zeolite A. • The LCDWG and SB were shown to be a feasible source of Al 2 O 3 and SiO 2 for the synthesis of zeolite A. • The DOE was determined using the BBD method in conjunction with response surface design. • This paper proposes a feasible model describing the crystallization of zeolite A. • Optimal zeolite A synthesis conditions included a Si/Al molar ratio of 2.0, temperature of 120°C, and synthesis time of 36 h.

Khaleque A., Alam M.M., Hoque M., Mondal S., Haider J.B., Xu B., Johir M.A., Karmakar A.K., Zhou J.L., Ahmed M.B., Moni M.A.

• Synthesis zeolites are uniform in size and produced in pure form. • Synthesis zeolites have better ion-exchange capacities than natural zeolites. • Effective synthetic routes for zeolites synthesis are discussed. • Comparative analysis of various raw materials for zeolite synthesis are included. • Synthetic zeolite has potential environmental applications. Zeolites with the three-dimensional structures occur naturally or can be synthesized in the laboratory. Zeolites have versatile applications such as environmental remediation, catalytic activity, biotechnological application, gas sensing and medicinal applications. Although, naturally occurring zeolites are readily available, nowadays, more emphasis is given on the synthesis of the zeolites due to their easy synthesis in the pure form, better ion exchange capabilities and uniform in size. Recently, much attention has also been paid on how zeolite is being synthesized from low-cost material (e.g., rice husk), particularly, by resolving the major environmental issues. Hence, the main purpose of this review is to make an effective resolution of zeolite synthesis methods together with potential applications in environmental engineering. Among different synthesis methods, hydrothermal method is commonly found to be used widely in the synthesis of various zeolites from inexpensive raw materials such as fly ash, rice husk ash, blast furnace slag, municipal solid waste, paper sludge, lithium slag and kaolin. Besides, future expectation in the field of synthetic zeolites research is also included.

Sayehi M., Garbarino G., Delahay G., Busca G., Tounsi H.

The present work reports the feasibility of valorizing waste glass and aluminum scraps into zeotype materials. The raw materials were reacted hydrothermally at 60 °C using alkaline fusion prior to hydrothermal treatment. The obtained powders were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), electron microscopy (SEM) and magic angle spinning nuclear magnetic resonance (MAS NMR) of 27Al and 29Si nuclei. The influence of some parameters like alkalinity, reaction time and particle size on the nature of obtained zeolites has been also studied. The characterization methods demonstrated that the final products are aluminosilicate materials with a high cation exchange capacity containing Na-FAU and Na–P1 zeolites. The above results show that valorization of waste glass and aluminum scraps to obtain Na-FAU and NaP1 zeolites is possible and can be a sustainable alternative to the traditional synthesis methods.

Taylor J.H., Elmes V.K., Hurt A.P., Coleman N.J.

The hydrothermal formation of mineral products from a mixture of amber container glass and aluminium waste (Al:Si = 1) in 4 M NaOH(aq) or 4 M KOH(aq) at 100 °C was monitored at 1, 3 and 10 days by X-ray diffraction analysis with Rietveld refinement, Fourier transform infrared spectroscopy and scanning electron microscopy with energy dispersive X-ray analysis. In NaOH(aq), at 1, 3 and 10 days, respectively, 48%, 55% and 63% of the glass crystallised to form hydroxysodalite (HS) and hydroxycancrinite (HC) with minor proportions of katoite and tobermorite. The partial successive transformation of HS to HC was also observed with time. The initial rates of dissolution of the glass and formation of the principal zeolite K-F and secondary katoite phases were considerably slower in KOH(aq); although, the subsequent development of the products was greater than that in NaOH(aq). The zeolite K-F product achieved only 5% crystallinity within the first day which then increased markedly to 60% and 78% at 3 and 10 days, respectively. Despite the incomplete conversion of amber glass into crystalline zeolitic phases, the uptake capacities of the 10-day feldspathoid and zeolite K-F products for Pb2+ (4.3 and 4.5 meq g-1, respectively) and Zn2+ (3.9 and 4.1 meq g-1, respectively) ions compared favourably with those of many other zeolites and waste-derived inorganic sorbents reported in the literature.

Sayehi M., Tounsi H., Garbarino G., Riani P., Busca G.

The waste materials available as sources of silicon and aluminum for producing porous materials like amorphous silicas, aluminas, amorphous silica-aluminas, and zeolites, to be used as catalyst and adsorbents, are briefly summarized. The procedures for preparing these materials from wastes are also taken into account. The limits of this approach in terms of economy and environmental protection are also briefly considered. It is concluded that mesoporous materials can be prepared from wastes, but care to product quality and to overall process efficiency is needed.

El-Nahas S., Osman A.I., Arafat A.S., Al-Muhtaseb A.H., Salman H.M.

Herein, we proposed an affordable and facile way of treating the hardening of water from local groundwater and seawater sources. This was facilitated by synthesizing zeolitic materials via an effortless and affordable method from readily available disposed of waste materials. Firstly, by converting waste aluminium (scrap wire cables, takeaway foil, cans, and spray aerosol bottles) along with disposed of silica gel into active zeolitic materials with the aid of a conventional domestic microwave. Small amounts of the produced zeolites (NaX and NaA) were utilized in the removal of the hardness of water (10 g.L−1), showing elimination of Ca2+ and Mg2+ ions within 30 min, removing 90 % of the total hardness (> 1000 ppm). The spent zeolite samples can be further used for more than two consequent cycles, then the regeneration can be promoted by using NaCl solution at ambient conditions. The total price for the synthesis of 1 kg of the zeolite produced herein is 14 $/kg. This is 70 % lower than the price of commercial zeolites available in the market. Our proposed facile route in zeolite preparation could potentially change the traditional costly softening treatment techniques. It also minimizes the use of extra chemical materials, templates and multi-step procedures. The excellent hardness removal capacity in groundwater and seawater using synthesized zeolite samples could open doors for various applications.

Reiprich B., Weissenberger T., Schwieger W., Inayat A.

The creation of intergrown layer-like zeolite crystals is one route to form hierarchical zeolites. Faujasite-type (FAU-type) zeolites are among the industrially most important zeolites and the implementation of hierarchical porosity is a promising way to optimise their catalytic and adsorptive performance. After a short general survey into routes for the preparation of hierarchical pore systems in FAU, we will review the currently existing strategies for the synthesis of FAU with layer-like morphology. Those strategies are mainly based on the presence of morphology modifying agents in the synthesis mixture. However, a very recent approach is the synthesis of layer-like FAU-type zeolite crystals assembled in an intergrown manner in the absence of such additives, just by finely adjusting the crystallization temperature. This additive-free preparation route for layer-like FAU, which appears very attractive from an ecological as well as economic point of view, is highlighted in this review. Concluding, a comparison, including powder X-ray diffraction, scanning and transmission electron microscopy, nitrogen physisorption and elemental analysis, between conventional FAU and three layer-like FAU obtained by different synthesis routes was carried out to show the structural, morphological and textural differences and similarities of these materials.

Kang Y., Swain B., Im B., Yoon J., Park K.H., Lee C.G., Kim D.G.

In the current investigation, we synthesize zeolite using two different waste streams, such as aluminum dross and waste glass powder, for its potential application in indium and tin recovery from the leach liquor of waste liquid crystal display (LCD) glass. The aluminum dross (Al resource) and waste glass powder (Si resource) were used as raw materials for the synthesis of zeolite. Zeolite was synthesized using different weight ratios of Al dross and waste LCD glass by hydrothermal synthesis route using NaOH. The weight ratio variations of Al dross and waste LCD glass in this study are 0.3:1, 0.5:1, 1:1, 2:1, 3:1, and 4:1 using 2 M NaOH hydroxide by the hydrothermal technique. The synthesized zeolite was analyzed by X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) followed by the possible application for recovery/extraction of indium and tin from leach liquor of waste LCD glasses. The indium extraction of average 93.66%, and tin extraction of 93.10% could be achieved from mixed solution indium and tin chloride. The significant achievement of the current investigation is that it can address two environment problems simultaneously, i.e., waste LCD glass and Al dross, and can be used for value recovery from waste LCD, LCD etching waste like secondary resources.

Xing P., Wang C., Zeng L., Ma B., Wang L., Chen Y., Yang C.

The continuously increasing demand for lithium has made it one of the strategic metals, rendering its exploitation of critical importance. Natural α-spodumene is still the primary resource of lithi...

Liu Y., Han S., Guan D., Chen S., Wu Y., Yang Y., Jiang N.

A seed-induced rapid synthesis of submicron ZSM-5 zeolites from acid-leached illite clay was achieved via solid-like state conversion. The optimal synthesis conditions and crystallization mechanism were investigated. The synthesized ZSM-5 zeolites were characterized using X-ray diffraction, scanning electron microscopy, N2 adsorption–desorption, X-ray fluorescence, NH3 temperature-programmed desorption, and 27Al MAS NMR. The results clearly indicated that well-dispersed submicron-size ZSM-5 zeolites were synthesized in the relatively short period of 6 h. In the solid-like state conversion synthesis system induced by crystal seeds, the sample gradually transformed from amorphous to well-dispersed submicron ZSM-5 as the crystallization time increased. Aluminum entered the ZSM-5 zeolites framework to provide acidic sites. The obtained ZSM-5 zeolites showed slightly better catalytic performance in toluene disproportionation than ZSM-5 seeds.

Król M.

The aim of this study was to obtain suitable absorbent material for environmental applications. The results of synthesis of zeolite granulate from expanded glass aggregate using hydrothermal method under autogenous pressure was presented. The resulting materials were analyzed regarding phase composition. In particular, the structures of materials were examined using FT-IR spectroscopy. This method is particularly useful for following the progress in a crystallization process. The results were compared to the XRD measurements, as well as SEM observations. The effects of synthesis temperature and time, as well as Si/Al and Na/Si ratios on the obtained products were determined. It has been found that by using suitable chemical composition is possible to efficiently zeolite synthesis at 70 °C. The type of resulting zeolite structure was identified based on XRD measurements and confirmed by analysis of the mid infrared spectra. Pseudolattice range, i.e. 800–400 cm−1, was detailed analyzed. In this range, there are bands associated with the ring vibrations, which are characteristic for secondary building units (SBU) occurred in zeolite structure. Depending on the composition of the reaction system, temperature and time, zeolite X, A, Na-P1 and hydroxysodalite have been identified as synthesis products. Practical aspects of heavy metal catitons sorption onto material synthesized in selected conditions will be presented. The atomic absorption spectroscopy (AAS) has been used as method, from which the concentration of ions in solution before and after sorption process and thus the effective cation exchange capacity (CEC) have been determined. The results were compared with the ones obtained for other zeolite materials. It was found, that zeolitic granules on the basis of expanded glass have very good sorption properties.

Lv N.Q., Zhou T.G., Liu H., Li T.T., Zhang Y., Zhao Y., Sun J.W., Xi B.D.

Coal fly ash was the main burning by-products in a coal-fired power station, which is a major global environmental problem and is threat to public health and environmental pollution. In this study, the optimum condition of synthesized zeolite from fly ash were investigated. The results showed that the optimum conditions were that the OH-concentration, the Si/Al ratio, the solid liquid ratio and aging time were 0.75 mol/L, 2.8, 9 ml/g and 0.5 h, respectively, for the synthesis of zeolites X. It is suggested that this method for synthesized zeolite X from coal fly ash is an efficient technology.

Majdinasab A., Yuan Q.

The present work investigated the microwave (MW) zeolitization of waste glass cullet using landfill leachate as a new potential solvent. The leachate-based zeolites were synthesized in two sets, one with metal precipitation and filtration (F-zeolite) and the second one with unfiltered metal precipitates (UF-zeolite). These two cases were compared with reference zeolites produced using deionized water (D-zeolite) in terms of their characteristics. Different characterization techniques were used including XRD, EDX, SEM, FTIR, TGA, and cation exchange capacity (CEC). Presence of cations other than Na+ in leachate elevated the generation of hot spot zones and synthesized highly crystalline zeolites using unfiltered leachate. Substantial reduction in Na+ concentration due to the solid filtration also favored the production of a roughly single-phase hydroxysodalite (HS) and suppressed zeolite NaP1 formation using filtered leachate. Deionized water also produced a small fraction of zeolite NaP1 due to the lower Na+ content compared to unfiltered leachate. Zeolite synthesized using unfiltered leachate was also superior in cation exchange and water holding capacities due to its least Si/Al ratio as confirmed by EDX, TGA, and CEC results. The results from this study contribute to shed light on the efficiency of leachate application for large-scale zeolite synthesis in future prospect.

Majdinasab A.R., Yuan Q.

The present work studied the conversion of waste glass (WG) cullet into zeolite using microwave (MW) radiation technique. The temperature and power of radiation were monitored through constant temperature (MWCT) and constant power (MWCP) modes. Indirect fusion synthesis (IFS) and direct hydrothermal synthesis (DHS) conversion methods were studied and the zeolites synthesized by these methods were compared in terms of their characteristics using various techniques including XRD, EDX, SEM, FTIR, TGA, and cation exchange capacity (CEC). IFS was an efficacious synthesis technique and produced zeolites with a much higher crystal growth efficiency compared with those synthesized by DHS method. The IFS method was better than the DHS method as it eliminated the inhibitive effect of soluble aluminates on Si release. The IFS zeolites also provided lower Si/Al ratio and consequently higher cation exchange and water holding capacities compared to DHS zeolites, as validated by EDX, TGA, and CEC results. In addition, high pressure and high-temperature environment deteriorated the zeolite structure and diminished the crystal growth performance. The application of cooling air jet (CAJ) through MWCP mode provided efficient monitoring of temperature overshoot and excessive pressure generation by cooling the excessive generated hot spot zones. Therefore, the CAJ application improved the crystal growth in IFS method as higher radiation powers were applied.