Zeolite Products Research Articles

Use of Incineration MSW Ash: A Review

This study reviews the characteristics of municipal solid waste incineration (MSWI) ashes, with a main focus on the chemical properties of the ashes. Furthermore, the possible treatment methods for the utilization of ash, namely, separation processes, solidification/stabilization and thermal processes, are also discussed. Seven types of MSWI ash utilization are reviewed, namely, cement and concrete production, road pavement, glasses and ceramics, agriculture, stabilizing agent, adsorbents and zeolite production. The practical use of MSWI ash shows a great contribution to waste minimization as well as resources conservation.

Mesopore generation by organosilane surfactant during LTA zeolite crystallization, investigated by high-resolution SEM and Monte Carlo simulation

The crystallization of LTA zeolite under a hydrothermal synthesis condition that contained a quaternary ammonium-type organosilane surfactant was studied with X-ray powder diffraction (XRD), high-resolution scanning electron microscopy (HRSEM) and Monte Carlo simulation of the crystal growth. The hydrothermal reaction products were collected at various crystallization times, and investigated with XRD and HRSEM. The HRSEM images of the final zeolite products were taken as synthesized and also after cross-sectioning with an argon ion beam. The HRSEM investigation revealed presence of a disordered network of mesoporous channels that penetrated the microporous zeolite crystal. Unless the loading of the surfactant was exceedingly high, the microporous zeolite particles exhibited truncated cubic morphologies that were almost like single crystals, despite penetration by the mesopores. The outline of the zeolite particle became progressively rounded as the mesoporosity was increased according to the surfactant loading. The mesoporosity in the zeolite crystals was well maintained against crystal-ripening processes for 6 d. This result supports the fact that the organosilane surfactant micelles became incorporated inside the zeolite crystal as a mesopore generator during the crystallization process. Data from Monte Carlo simulation agreed with these experimental results.

Measuring sub-lethal effects on freshwater crayfish (Paranephrops planifrons) behaviour and physiology: laboratory and in situ exposure to modified zeolite

Various behavioural and physiological tests were applied to determine whether an aluminised modified zeolite clay product (Z2G1), used to cap phosphorus release from lake sediments, had sub-lethal effects on adult freshwater crayfish (Paranephrops planifrons). In situ exposures of caged crayfish before and after application of modified zeolite to Lake Okaro, Central North Island, New Zealand, at a nominal application concentration of 350 g m−2, did not impact the survival of freshwater crayfish or produce any significant sub-lethal effects on crayfish mobility or physiology that we could detect. In laboratory sediment tests, crayfish did not show any consistent effect from short-term (10 days) exposure to modified zeolite (at concentrations of 350, 700 or 2,100 g m−2) or to alum. When combined, the field and laboratory data provide strong evidence that applications of 350 g m−2 modified zeolite will have no short-term effect on adult crayfish, with a ‘margin of safety’ for higher application rates. Chronic exposure effects of capping agents and the indirect impacts of lake treatment (e.g. food web responses) are yet to be determined. Quantitative measures of shade- and shelter-seeking behaviour, righting behaviour, and length of escape response, could be improved by the addition of standardised behavioural observations. Physiological measures of ammoniacal-N production and oxygen consumption are less variable than behavioural tests, but comparisons between treatments are best conducted simultaneously. A suite of behavioural and physiological sub-lethal measures using field and laboratory exposures is recommended to provide an integrated assessment of crayfish health.

Zeolite Formation from Coal Fly Ash and Its Adsorption Potential

The possibility in converting coal fly ash (CFA) to zeolite was evaluated. CFA samples from the local power plant in Prachinburi province, Thailand, were collected during a 3-month time span to account for the inconsistency of the CFA quality, and it was evident that the deviation of the quality of the raw material did not have significant effects on the synthesis. The zeolite product was found to be type X. The most suitable weight ratio of sodium hydroxide (NaOH) to CFA was approximately 2.25, because this gave reasonably high zeolite yield with good cation exchange capacity (CEC). The silica (Si)-to-aluminum (Al) molar ratio of 4.06 yielded the highest crystallinity level for zeolite X at 79% with a CEC of 240 meq/100 g and a surface area of 325 m2/g. Optimal crystallization temperature and time were 90 °C and 4 hr, respectively, which gave the highest CEC of approximately 305 meq/100 g. Yields obtained from all experiments were in the range of 50–72%.

Dry gel conversion synthesis of shape controlled MFI type zeolite materials

Acid treated silica fibers, coming either from asbestos cord waste or calcium aluminosilicate glass, were engaged as reactants to product MFI type zeolite fibers applying a dry gel conversion (DGC) type synthesis. The impact of amorphous silica fiber shape and synthesis conditions on morphology of the final product was investigated. Enhanced zeolite nucleation and restricted crystal growth are necessary to maintain the initial fiber morphology. Whereas a DGC type crystallization in hydroxide media results in the formation of zeolite fibers, the use of fluoride ions leads to the formation of large individual zeolite particles. Synthesis conditions have to be adapted to form zeolite particles with an average size smaller than the silica fiber diameter to allow a good conservation of the fiber morphology. Final zeolite fibers have textural properties comparable to a standard zeolite product and are promising for adsorption applications.

Removal of heavy metals from wastewater using CFB-coal fly ash zeolitic materials

Polish bituminous (PB) and South African (SA) coal fly ash (FA) samples, derived from pilot-scale circulated fluidized bed (CFB) combustion facilities, were utilized as raw materials for the synthesis of zeolitic products. The two FAs underwent a hydrothermal activation with 1M NaOH solution. Two different FA/NaOH solution/ratios (50, 100g/L) were applied for each sample and several zeolitic materials were formed. The experimental products were characterized by means of X-ray diffraction (XRD) and energy dispersive X-ray coupled-scanning electron microscope (EDX/SEM), while X-ray fluorescence (XRF) was applied for the determination of their chemical composition. The zeolitic products were also evaluated in terms of their cation exchange capacity (CEC), specific surface area (SSA), specific gravity (SG), particle size distribution (PSD), pH and the range of their micro- and macroporosity. Afterwards the hybrid materials were tested for their ability of adsorbing Cr, Pb, Ni, Cu, Cd and Zn from contaminated liquids. Main parameters for the precipitation of the heavy metals, as it was concluded from the experimental results, are the mineralogical composition of the initial fly ashes, as well as the type and the amount of the produced zeolite and specifically the mechanism by which the metals ions are hold on the substrate.

Laboratory assessment of insecticidal effectiveness of natural zeolite and diatomaceous earth formulations against three stored-product beetle pests

The insecticidal effectiveness of two natural zeolite formulations (Minazel plus and Minazel), applied to wheat at selected rates of 0.25, 0.50 and 0.75 g/kg, and a diatomaceous earth formulation (DE) (Protect-It™), applied at the recommended rates of 0.15 g/kg for Sitophilus oryzae, 0.20 g/kg for Rhyzopertha dominica and 0.30 g/kg for Tribolium castaneum, were tested under laboratory conditions (24 ± 1 °C temperature and 45 ± 5% relative humidity). The highest adult mortality was observed after the longest exposure period of 21 days and 7 days of recovery, when all three zeolite dosage rates and the recommended DE dosage caused 97–100% mortality of S. oryzae and 94–100% of T. castaneum. On the other hand, 100% mortality was not achieved in any test variant involving R. dominica; the highest (about 92%) was detected for DE, while 52% and 79% mortality was achieved with the zeolites at the highest rate of 0.75 g/kg. Progeny reduction by >90% was achieved after 21 days of contact of all three beetle pests with DE-treated wheat, while the same level of reduction was achieved for S. oryzae and T. castaenum only after contact with the highest rate of the zeolite product, Minazel. Thus the two zeolite formulations are comparable to diatomaceous earth in controlling adult S. oryzae, R. dominica and T. castaneum, but only the Minazel formulation could effectively protect wheat from attack by S. oryzae or T. castaneum, and only with a higher rate of application than for the DE formulation.

Synthesis of ZSM-5 zeolite and silicalite from rice husk ash

Local rice husk was precleaned and properly heat treated to produce high purity amorphous SiO2 for use in the synthesis of ZSM-5 zeolite and silicalite by hydrothermal treatment (150°C) of the precursor gels (pH 11) under autogenous pressure in a short reaction time (4–24h). A wide range of SiO2/Al2O3 molar ratios (30–2075) and a small template content were employed to fully exploit the potential of rice husk ash (RHA). The mineralogical phases, morphology, specific surface area and pore volume of the synthesized products were investigated by XRD, FT-IR, SEM and BET analyses, respectively. Under the employed conditions, it was found that the gels with a low range of SiO2/Al2O3 molar ratios (<80) produced an amorphous phase to poorly crystalline ZSM-5 zeolite; those with a medium range (80–200) favored well crystalline ZSM-5 zeolite production with a large surface area; whilst those with a high range of SiO2/Al2O3 molar ratios (>200) yielded silicalite. The increase in Na2O content, which was derived from the addition of NaAlO2 to attain the desired SiO2/Al2O3 molar ratio of the gel, did not significantly enhance the crystallization rate, crystallinity, or yield of products. On the contrary, these properties were greatly affected by the increase in the SiO2/Al2O3 molar ratio.

IR and XRD Amorphous Synthesis Residue Showing Zeolitic Micropores

AbstractIn the preparation of zeolite nanocrystals from the hydrothermal reaction of clear solution, the zeolite products are typically collected by high speed centrifugation. For Beta zeolite, the crystalline yield is often low, thus a good fraction of silicates reminds in the supernatant. These XRD amorphous materials turn out to be uniform nanoparticles that, after calcination, showed similar micropore structure as that of the collected beta zeolite nanocrystals. TPD measurements of hexane isomers further indicated that both the crystalline and the amorphous products were more selective toward the smaller hexane molecule.

Formation of linde F zeolite by KOH treatment of coal fly ash

Zeolitic products formed by hydrothermal treatment of coal fly ash (FA) with KOH aqueous solution under various reaction conditions were examined. Only linde F-type zeolite (K2Al2Si2O8·3H2O) was newly formed at atmospheric pressure, except formation of a small amount of kalsilite (KAlSiO4) at longer reaction time. The yield of the linde F zeolite was highest when reaction time, temperature, KOH concentration and (KOH solution / FA) ratio were 48 h, 95°C, 8 mol dm-3 and 25 ml g-1, respectively. In this case, the original FA spheres were almost completely dissolved out, and regular prisms of the linde F zeolite crystal with 0.5 to 1 μm in width and 1 to a few μm in length were formed. The specific surface area and cation exchange capacity of the FA-derived linde F zeolite were 20.2 m2 g-1 and 2.3 meq g-1, respectively.

Differential behaviour of combustion and gasification fly ash from Puertollano Power Plants (Spain) for the synthesis of zeolites and silica extraction

Coal gasification (IGCC) and pulverised coal combustion (PCC) fly ashes (FAs), obtained from two power plants fed with the carboniferous bituminous coal from Puertollano (Spain), were characterised and used as raw materials for zeolite synthesis by direct conversion (DC) and by alkaline fusion (Fu), and SiO 2 extraction (Si-Ex) at laboratory scale. The Puertollano FAs are characterised by a high SiO 2 content (59%) with respect to EU coal FAs. High zeolite synthesis yields were obtained from both FAs by using conventional alkaline activation. However, the Si extraction yields were very different. The results of the zeolite synthesis from the Si-bearing extracts from both FAs demonstrated that high purity zeolites with high cation exchange capacity (CEC, between 4.3 and 5.3 meq/g) can be produced. The solid residue arising from Si-Ex is also a relatively high NaP1 zeolite product (CEC 2.4–2.7 meq/g) equivalent to the DC products. The zeolitic materials synthesised from both FAs by Fu showed an intermediate (between the high purity zeolites and the DC products) zeolite content with CEC values from 3.4 to 3.7 meq/g. Low leachable metal contents were obtained from high purity A and X zeolites and zeolite material synthesised by Fu for PCC FA.

FER zeolite crystallized in THF–Na 2O–SiO 2–Al 2O 3–H 2O reactant system containing catalytic amount of organic additives

Pure-phase FER zeolite was hydrothermally synthesized in the reactant system of Na 2O–SiO 2–Al 2O 3–H 2O with tetrahydrofuran (THF) as the template in the presence of catalytic amount of glycerol [CH 2(OH)CH(OH)CH 2(OH), GC] or OP emulsion agent [C 8H 17–C 6H 5–O–(CH 2CH 2O) 10OH, OP] in the temperature range of 413–473 K. Powder X-ray diffraction (XRD) was used to observe the crystallization products, and scanning electron microscope (SEM), 13C cross polarization (CP) and 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR), X-ray fluorescence scattering spectroscopy (XRF), thermal analysis and nitrogen adsorption were used to characterize the synthesized zeolite. The promoting role of the catalytic amount of additives in the zeolite crystallization was investigated on the restraining co-crystallization of MOR zeolite impurity, lowering the reaction temperature to 413–433 K, shortening the crystallization period to 24 h at 413 K, and modifying the morphology and the adsorption properties of the yielded zeolite products. The mechanism of the promoting role of the catalytic amount of organic additives is also discussed.

Synthesis of Zeolite from Aluminium Etching By-Product: The Effect of Reaction Temperature on Crystallinity and Its CO2 Adsorption Property

The synthesis of zeolite from the by-product of aluminium etching process was investigated. The starting by-product reactant had high aluminium content, 92.17% wt. as Al2O3. Si and Na compositions were adjusted by the addition of sodium metasilicate, in the hydrogel process.The reaction time was fixed at 1 h., while the stirring speed was controlled at 200 rpm. and the temperature varied in the range of 60-90°C. The mole ratio of the starting reactants were also fixed at 2 (SiO2/Al2O3 = 2, Na2O/ Al2O3 = 2). The product properties were found to depend on reaction temperature. The better zeolite product in the range of these experiments was found at 90°C, containing 75% crystallinity as referred to the commercial zeolite A. The percentage crystallinity of the synthesized zeolite was found to increase with increasing reaction temperature. Analysis of the XRay diffraction (XRF) and FT-IR spectra confirmed that the synthetic zeolite was of type A. The CO2 (99.5% purity) absorption test was performed with the zeolite sample synthesized at 90°C, using N2 (99.9% purity) as carrier at total flow rate of 15 cc min−1, resulting in 0.00386 mole of CO2 adsorption g−1. The study showed the potential of developing the by-product of aluminium etching process into a higher value added product of zeolite A. Further economic study of the process was suggested.

Structural Evolution of Fly Ash Based Geopolymers in Alkaline Environments

The effects of immersion in alkaline solutions on the gel structure and pore network of fly ash based geopolymers are investigated. Immersion in carbonate or hydroxide solutions of up to pH 14 results in very little leaching of framework components (Si or Al) from the geopolymer gel, and a largely unchanged mesoporous gel structure. Higher concentrations, up to 8 M NaOH, cause more damage to the gel framework as species are leached into solution and the pore network collapses. Crystallization of small quantities of zeolites from the initially X-ray amorphous gel is also observed. The zeolitic products formed are in general the same products that are observed in geopolymers cured at elevated temperatures for extended periods of time, suggesting that the reactions taking place during alkaline immersion are to some extent a continuation of the initial geopolymerization process.

Editorial

As the most important nanoporous material, zeolites, which have intricate micropores, are essential heterogeneous catalysts in industrial processes. Zeolites are generally synthesized with organic templates under hydrothermal conditions; however, this method is environmentally unfriendly and costly due to the formation of harmful gases and polluted water. This article briefly summarizes the role of organic templates and describes designed routes for the organotemplate-free synthesis of zeolites, aided by zeolite seeds and zeolite seeds solution. Furthermore, this review explicates that the micropore volume decreases with an increase of the Si/Al ratios in the organotemplate-free synthesis of zeolite products, where Na+ exists as an alkali cation. This feature is very important in directing the synthesis of zeolite catalysts with controllable Si/Al ratios under organotemplate-free conditions, and is thus important for the efficient design of zeolites.

ZEOLITE SYNTHESIS FROM PAPER SLUDGE ASH VIA ACID LEACHING

Paper sludge ash (PSA) typically has a low Si abundance and significant Ca content due to the presence of calcite fillers. Acid leaching with HCl was used to reduce the Ca content so that a zeolitic product with a high cation exchange capacity (CEC) could be synthesized. Zeolitic products were synthesized from raw ash and leached ash through reaction with 2.5 M NaOH solution at 80°C. In the case of the original ash without acid leaching, the concentration of Al in the alkali solution always exceeded that of Si during the synthesis, and hydroxysodalite with a low Si/Al ratio (1:1) was formed. In the case of the leached ash, the concentration of Si always exceeded that of Al during the synthesis, and zeolite-P with a higher Si/Al ratio (5:3) was formed. Hydroxysodalite and zeolite-P crystallization was saturated after 6 h of reaction, and the product from leached ash had a higher CEC (approximately 150 cmol/kg) than that from original ash (approximately 40 cmol/kg). Both the decrease in the Ca phase in the leached ash and the corresponding increase in the Si and Al amorphous phases play an important role in zeolite synthesis.

Synthetic zeolites as a new tool for drug delivery

Synthetic zeolites were studied in order to investigate their ability to encapsulate and to release drugs. In particular, a zeolite X and a zeolitic product obtained from a cocrystallization of zeolite X and zeolite A were examined. These materials were characterized by chemical analyses (ICP-AES), X-ray diffraction, nitrogen adsorption isotherm, scanning electron microscopy, laser diffraction, and infrared spectroscopy. Since ketoprofen was chosen as a model drug for the formulation of controlled-release dosage forms, it was encapsulated into these two types of synthetic zeolites by a soaking procedure. Drug-loaded matrices were then characterized for entrapped drug amount and thermogravimetric behavior. In both types of activated zeolites, the total amount of ketoprofen (800 mg) was encapsulated in 2 g of matrix. By using HPLC measurements, ketoprofen release studies were done at different pH conditions so as to mimick gastrointestinal fluids. The absence of release in acid conditions and a double phased release, at two different pH values (5 and 6.8), suggest that after activation these materials offer good potential for a modified release delivery system of ketoprofen.

Adsorptive removal of thiophene and benzothiophene over zeolites from Mae Moh coal fly ash

Zeolites have been hydrothermally synthesized using Thai coal fly ash from Mae Moh Power Plant as silica and alumina sources. The synthesis conditions, i.e., SiO2/Al2O3 ratio, amount of water, amount of base, and aging temperature, were varied to prepare different topologies of zeolitic products. The zeolites attained were sodalite (SOD), gismondine (GIS), and cancrinite (CAN). The zeolites have been applied to adsorption of thiophene and benzothiophene in n-hexane solution. It was found that GIS with higher specific surface area and average pore volume had superior performance to other synthesized materials. Adsorption capacity of our developed zeolites was compared to those of commercial zeolites, i.e. NaY, HUSY, beta, and ZSM-5 obtained via the conventional synthesis methods. The results suggested a potential of zeolites derived from Mae Moh coal fly ash for removal of refractory sulfur compounds, such as benzothiophene.

포트랜드 시멘트를 이용한 천연 지올라이트 미분의 입단화

Enormous amounts of zeolite by-products as a fine powder have been produced while manufacturing commercial zeolite products. Granulation of the zeolite by-products is necessary in order for them to be recycled as soil conditioners or absorbents for various environmental contaminants due to the limitations inherent from their physical properties. We granulated the zeolite powders using Portland cement as a cementing agent and characterized the physical and chemical properties of the granulated zeolite product. The experimental natural zeolite had a Si/Al ratio of 4.8 and CEC of 68.1 cmolc kg -1 .T he X-ray diffractometry (XRD) revealed that clinoptilolite and mordenite were the major minerals of natural zeolite. Smectite, feldspar and quartz also existed as secondary minerals. Optimum conditions of granulated zeolite production occurred when natural zeolite was mixed with Portland cement at a 4:1 ratio and granulated using the extruder, left to harden for one month at 25°C and treated at 400°C for 3 hours. The wide spectra of XRD revealed that the granulated zeolite had amorphous oxide minerals. The alkali- or thermal-treated natural zeolite exhibited pH-dependent charge properties. The major minerals of the granulated zeolite were clinoptilolite, mordenite and tobermorite. The buffering capacity and charge density of the granulated zeolite were greater than those of natural zeolite.

Open System 수열반응을 통한 하수슬러지 소각 비산재의 Zeolite 합성가능성

The sewage treatment sludge disposal has become a serious environmental problem because of restricted direct land-filling and oceandumping in spite of their large amounts discharged. So the recycling of sewage treatment sludge is very useful alternative for waste management. Here, we studied the feasibility of zeolite synthesis in open system from the sewage treatment sludge incinerator fly ash by means of hydrothermal synthesis. We considered the concentration of NaOH, reaction time, reaction temperature and reaction step as synthesis variables. The phase of zeolite products was identified by X-ray diffractometer(XRD) and ammonium ion exchange test was performed for the raw fly ash and two zeolite products(Z-3 and Z-5). In leaching test of the raw fly ash, hazard metal is detected very low level compared with regulatory leaching test standard. But in total recoverable test, the total contents of the fly ash were very high in terms of the standard for waste-derived fertilizer. Through hydrothermal reaction, small amount of zeolite P was synthesied in 1 N of NaOH solution and relatively large amount of hydroxysodalite was synthesied in 3 N and 5 N of NaOH solution with similar peak intensity. Addition of an aging step in the synthesis didn't increase the amount of zeolite phase. Maximum <TEX>$NE_4^+-N$</TEX> exchange capacity is 1.49 mg <TEX>$NH_4^+-N/g$</TEX> in Z-3 and 1.38 mg <TEX>$NH_4^+-N/g$</TEX> in Z-5. Most of the ammonium ion is exchanged in 30 minutes and disorption did not occur until 5 hours.