Fly Ash-based Zeolite Research Articles

The coupling action mechanism of NaOH/NaNO3 on the hydrothermal synthesis of fly ash-based zeolites and the Sr-Na exchange capacity

The treatment of low- and intermediate-level radioactive waste from nuclear power plants using fly ash-based zeolite involves issues related to product evolution and cation exchange. This study aims to elucidate the evolution of hydration products and the interaction mechanism between Sr²⁺ and Na⁺ in fly ash-based zeolite under the regulation of NaOH/NaNO₃. The fly ash-based zeolites were characterized using XRD, IR, and SEM. The adsorption capacity and chemical binding energy before and after Sr²⁺ adsorption were analyzed using ICP and XPS, respectively. The results demonstrated that the main products in fly ash-based zeolite influenced only by NaOH undergo a transformation from Faujasite to Na-P1 zeolite, and finally to Sodalite. However, when NaOH/NaNO₃ were added simultaneously, the main product first transformed from Faujasite to Na-P1 zeolite, and then into Sodalite or Cancrinite as the Na/Al ratio increased. Furthermore, the adsorption process of fly ash-based zeolite influenced solely by NaOH followed the Langmuir isotherm model, while the adsorption process affected by both NaOH /NaNO₃ followed the Freundlich isotherm model. Among these, Na-P1 zeolite showed the most favorable adsorption performance for Sr²⁺. As Sr²⁺ adsorption increases, the fly ash-based zeolites exhibit the appearance of Sr-O bonds. These findings offer a new perspective for enhancing the nuclide immobilization capacity of fly ash-based geopolymers through the adjustment of salt and alkali concentrations.

Optimization of Pelleting Parameters for Producing Composite Pellets Using Zeolitic Material From Fly Ash

Zeolitic material in powder form was prepared from fly ash by direct activation treatment. The resulted fly ash-based zeolite was pelletizing and the effect of different inorganic (calcium hydroxide, bentonite, kaolinite) and organic (dextrin) binders with varying percentage was investigated. The zeolitic materials were analyzed by XRF, XRD, SEM, FTIR, TG-DTG and Nitrogen adsorption/desorption isotherm. Compression and impact tests have been used to study the deformation and breakage behaviour of spherical granules. The best performance was obtained by zeolite granular containing 5 wt.% bentonite and 5 wt.% kaolinite with mechanical strength and satisfactory water resistance. The synthesis of pelletized zeolite from by-products derived from coal combustion provides not only environmental and economic benefits, but also contributes to achieving the principles of sustainable development.

N-Cetyltrimethylammonium Bromide-Modified Zeolite Na-A from Waste Fly Ash for Hexavalent Chromium Removal from Industrial Effluent

Chromium ions released into aquatic environments pose major environmental risks, particularly in developing countries. Here, a low-cost N-cetyltrimethylammonium bromide (CTAB)-modified fly ash-based zeolite Na-A (CTAB@FZA) was prepared for the treatment of industrial wastewater contaminated with Cr(VI). CTAB@FZA was evaluated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), which showed that CTAB intercalation and coating of the modified zeolite were successful. The effects of influencing variables on the removal of Cr(VI) using CTAB@FZA were also evaluated, including pH, initial concentration, time, temperature, and coexisting ions. Fast adsorption equilibrium was observed after less than 10 min, and CTAB@FZA had a maximum adsorption capacity of 108.76 mg/g and was substantially greater than that of pristine FZA following modification. Furthermore, isothermal and kinetic data demonstrated that Cr(VI) adsorbed onto homogeneous surfaces via rate-limiting monolayer Langmuir adsorption, and according to thermodynamic data, the sorption of the targeted pollutant was exothermic and spontaneous. The application of CTAB@FZA to industrial wastewater treatment yielded Cr(VI) concentrations that were below the USEPA standards. Overall, the findings demonstrated that CTAB@FZA is an effective, promising, and economical adsorbent for the treatment of Cr(VI)-polluted water.

ZnO-functionalized fly-ash based zeolite for ciprofloxacin antibiotic degradation and pathogen inactivation

There is an increasing need for photocatalytic materials capable to remove pollutants and to deactivate microorganisms for a wide range of applications. Here we report the preparation of fly ash-based zeolite material in which ZnO was incorporating using an alkaline hydrothermal method. The zeolitic materials were used to functionalized glass substrates through spin-coating technique and characterized by X-ray diffraction, emission spectroscopy, electrophoretic light scattering, and UV–Vis diffuse reflectance, among other techniques. The surface characteristics of the coatings were determined by scanning electron microscopy and water contact angle. The photocatalytic activity of ZnO-functionalized fly-ash based zeolite was assessed by tracking the degradation of the antibiotic ciprofloxacin (CIP) and its antimicrobial capacity by means of the inactivation of the bacteria Staphylococcus aureus and Escherichia coli under UVA (365 nm) irradiation. The results showed the formation of a sodalite zeolite structure with a band gap of 3.2 eV and photoinduced hydrophilicity. The ZnO-modified fly ash material was able to completely photodegrade CIP in less than 20 min irradiation with 365 nm UVA light, while its non-modified precursor, even displaying a high adsorption capacity was unable to remove the antibiotic after 120 min. The ZnO-zeolitic materials and coatings were able to inactivate bacteria with reductions in the number of viable colonies > 99.9 for S. aureus and > 99.0% for E. coli after 60 min of irradiation, even on specimens previously allowed to grow a mature biofilm. The zeolitic material also proved a low cytotoxicity to human fibroblast cultures.

Effects of aging time on the crystallization/transformation of hydrothermal synthesis alkali-activated fly ash-based zeolite

Zeolites with unique framework structure have wide applications, such as ions’ exchangers, molecular sieves and catalysts. This work focused on the synthesis and characterization of zeolite by recycling coal fly ash as the starting material via hydrothermal method. The intermediate phases and final products were characterized by XRF, XRD, FT-IR, SEM and BET techniques. The effects of aging time on the crystallization/transformation of zeolite were discussed. The results showed that the alkali-activated coal fly ash after hydrothermal process could lead to the formation of zeolite Na-P1. Furthermore, the aging treatment benefited the formation of homogenous zeolite Na-P1 with smaller particle size, larger specific surface area, total pore volume and pore size.

Synthesis of Fly Ash-Based Zeolite and its Research Progress in Wastewater Treatment

Fly ash is the most common solid waste in the industry, and its high value-added utilization has become a hot issue of study. Carrying out the green synthesis route of zeolite as the raw material of fly ash has become an extremely important scientific significance and practical value. In this paper, the research progress of fly ash-based zeolite was introduced from three aspects, including fly ash activation method, fly ash-based zeolite synthesis method and fly ash-based zeolite in the wastewater treatment sector. The relevant applications of fly ash-based zeolite as an adsorbent material in the treatment of wastewater pollution were summarized, and the development trend has prospected.

Green synthesize of fly ash-based zeolite X: a potential microwave absorbent

Zeolite X is a potential electromagnetic wave (EMW) absorption material owning to its advantages of good dielectric properties, light weight and large specific surface area. Herein, high-purity zeolite X was prepared from fly ash using a green synthesis approach, in which only trace water was used and achieved zero discharge of waste water. Physiochemical properties of fabricated zeolite X were comprehensively evaluated through XRD, PSD, SEM, TG-DSC and BET test. XRD pattern shows the successful preparation of zeolite X with good crystallinity and high purity, and the average particle size is ~ 2.45 μm, which conforms to Gaussian distributions. The fabricated zeolite X exhibits typical octahedral structure and good thermal stability. It is noteworthy that the specific surface area is up to 473.56 m2/g, representing porous structure, which is beneficial to EMW attenuation. What’s more, the abundant crystal water and adsorbed water existing in the sample is conductive to dipole polarization, which further consume EMW energy. The effective absorption bandwidth (EAB) of the synthesized zeolite X is 2.08 GHz (13.36–15.44 GHz) at the thickness of 2.5 mm. This study provides an eco-friendly approach to change waste into valuables, and moreover the synthesized zeolite X is a potential EMW absorbing material.

Iron-zirconium microwave-assisted modification of small-pore zeolite W and its alginate composites for enhanced aqueous removal of As(V) ions: Experimental and theoretical studies

The requirement for enhanced, low-cost, and eco-friendly materials are highly favored for water treatment processes. Then, for extended application prospects, a simple and cost-effective method for composites preparation is mainly investigated. In the present work, a rapid and efficient modification of fly ash-based zeolite W (ZW) was achieved using a microwave-assisted process and then was applied to remove arsenate (As(V)) from water. The exchange equilibrium was reached after 1 min at 150 °C under microwave heating, where the iron and zirconium contents were 6.9 and 5.04 wt%, respectively. The modified zeolite (FeZrZW) demonstrated an excellent efficiency toward As(V) ions up to 99.87% across a broad pH, from acidic 2 to basic 10. A high adsorption capacity of As(V) was obtained (Qm = 42.31 mg g−1) than all natural or fly ash-based zeolites, much higher than some commercial and synthetic adsorbents. The high arsenate uptake performance of FeZrZW adsorbent could be related to the creation of active acid sites on ZW after its modification containing iron and zirconium oxides, which capture through the formation of Zr-O-As and Fe-O-As bridges. Monte Carlo simulation results confirmed the stronger and spontaneous adsorption onto FeZrZW and gave more insights into the interaction between arsenic species and the adsorbents. In addition, [email protected] composites were suggested as an alternative solution to the separation problem of arsenate in solution. They proved a remarkable efficiency up to 99.87% and an adsorption capacity of 29.38 mg g−1. Finally, FeZrZW combines various exciting properties to be applied in a full-scale process for arsenic recovery.

High Catalytic Activity of a Seawater Fly Ash Based Zeolite for Phenol Alkylation

Zeolites have been used as catalysts and high cation-exchange materials because of their suitable structure, uniform pore size and high cation-exchange capacity. In this paper, type X zeolites synthesized from fly ash were employed as substrates for developing catalysts with improved performance. With the aim to determine potential application of synthetic products in catalysis, zeolites (with different values of BET surface area) were tested in the gas-phase as basic catalysts for phenol alkylation using diethyl carbonate as an innovative alkylating agents. The results indicate that the newly-formed zeolites are very selective for the O‑ethylation of phenol also at higher temperature. The catalytic activity of the zeolites synthesized from fly ash gives high yields, is clean, cost effective, environmentally friendly which make the fly ash-based zeolites efficient catalysts and alternatives for industrial applications.

Effective immobilization and reduction in bioavailability of Cd in a L. succinea growing in contaminated sediment by the application of alkali synthesized fly ash based zeolite (FABZ)

Abstract In the current study, a highly efficient and cost-effective zeolite derived from fly ash was used for immobilization of cadmium (Cd) in sediment of a pond. The potential of fly ash based zeolite (FABZ) was explored by in-situ amendment practice, including a study plan based on sediment-water microcosm study. The zeolite obtained after acid washing step (fly ash: acid, 1:10 g/mL) followed by the alkali fusion showed the high value of cation exchange capacity (CEC, 13.88 meq/g). The maximum monolayer uptake capacity was found as 145.931 mg/g, indicating the usefulness of FABZ in Cd enriched environment. The sediment treated with 10% FABZ showed remarkable decrease in Cd concentration (about 80%) as compared to the control (0% FABZ). The results of the sequential extraction in exchangeable fraction revealed that Cd level was decreased by 90.72% (10% FABZ) as compared to untreated one, hence successfully decreased the bioavailable Cd. Furthermore, in the muscles of Lymnaea succinea, Cd concentration of 0.87 mg/kg was observed (10% FABZ), which was found six times less than the mollusc of 0% FABZ treated sediment. Thus, prepared FABZ showed its potential to immobilize Cd from sediment and can be used as an economical and feasible method for sediment management at pilot scale.

Influence of aluminium source on the crystal structure and framework coordination of Al and Si in fly ash-based zeolite NaA

In this study zeolite NaA with different crystal sizes and % crystallinity was prepared from a clear solution extract of fused fly ash. Sodium aluminate or aluminium hydroxide was used to adjust the aluminium content in the fused fly ash extract and hence adjust the Si/Al ratio of the various synthesis molar regimes for the synthesis of zeolite NaA. Each molar regime was hydrothermally treated for 3h at 100°C. Chemical, mineralogical, morphological and structural composition of the synthesized products was determined using XRF, laser ablation ICP-MS, XRD, SEM and 29Si and 27Al NMR. This study showed that the variation of Si/Al ratio of the synthesis mixture (0.27 to 0.80) allowed control of zeolite NaA crystal/sizes that ranged from 0.67 to 3.18μm. The decrease in Si/Al ratio of the synthesis mixture was proportional to the crystal size (μm) and the 29Si NMR peak width and area of the synthesized zeolite NaA. The increase in crystallinity and decreases in crystal size caused the 29Si NMR peak width to be narrower as the peak area reduces. Interestingly, the Si/Al ratio of the synthesis mixture was inversely proportional to the crystallinity of zeolite NaA when Na-aluminate was used as Al source. The effect of Al source was also noticed by the appearance of a small additional distorted tetrahedral Al peak between 15 and 17ppm (27Al NMR) when Al-hydroxide was added to fused fly ash extract.

Transformation of South African coal fly ash into ZSM-5 zeolite and its application as an MTO catalyst

This study presents a way of using South African coal fly ash by extracting metals such as Al and Fe with concentrated sulphuric acid, and then using the solid residue as a feedstock for the synthesis of ZSM-5 zeolite. The percentage of aluminium and iron oxides decreased from 28.0 ± 0.2% and 5.0 ± 0.1% in coal fly ash to 24.6 ± 0.1% and 1.6 ± 0.01% in the acid treated coal fly ash respectively. The fly ash-based zeolite ZSM-5 sample synthesised from the solid residue after extraction of Al and Fe, contained 62% of ZSM-5 zeolite pure phase with a number of Brønsted acid site density of 0.61 mmol per gzeolite. By properly treating the as-prepared coal fly ash-based ZSM-5 zeolite, an active and selective methanol-to-olefins acid catalyst could be designed, leading to full methanol conversion during 15 h on stream. The optimised catalyst exhibited a cumulative methanol conversion capacity of 71 g(MeOHconverted)/g(catalyst) and a light olefin productivity of 21 g(C2=–C4=)/g(catalyst). Cette étude présente une stratégie de valorisation de cendres du charbon (origine : Afrique du Sud) après extraction de métaux tels que le fer ou l'aluminium. Le résidu solide est ensuite utilisé comme matière première pour synthétiser une zéolithe ZSM-5. Cette dernière est obtenue sous la forme d'un matériau composite zéolithe (62%)/cendre, présentant une acidité de Brønsted de 0,61 mmol par gzeolite. Par une conception sur mesure ou rational design, un composite ZSM-5/cendre s'est avéré être un catalyseur actif et sélectif dans la réaction de conversion du méthanol en oléfines légères (MTO). Une capacité totale de conversion du méthanol de 71g/gcatalyseur accompagnée d'une productivité de 21 g (C2=–C4=)/gcatalyseur a ainsi été obtenue.

Synthesis of zeolite A from coal fly ash using ultrasonic treatment – A replacement for fusion step

The synthesis of zeolites from fly ash has become an increasingly promising remedy to the crisis of coal fly ash production and disposal in South Africa. In recent studies, South African fly ash was proven to be a suitable feedstock for the synthesis of essential industrially used zeolite A. However, the process involves a costly energy intensive step whereby fly ash is fused at high temperatures, which may make the process economically unattractive on a large scale. The aim of this study is to investigate the possibility of replacing high temperature fusion with less energy intensive sonochemical treatment for the synthesis of zeolite A. Sonochemical treatment was first thought possible due to the violent cavitation caused by high intensity sonication. The results of the study showed that fusion can be replaced by 10min of high intensity sonication. The incorporation of sonication also consequently reduced the crystallization temperature of the process making it possible to synthesize a pure phase zeolite A at lower temperatures and reduced times. This study effectively developed a novel process to replace the energy intensive fusion step with a short, easy and inexpensive treatment. Scale up of this synthesis approach may proffer a promising alternative option to the anticipated energy demand of the synthesis of fly ash-based zeolite with fusion method.

Synthesis of carbon dioxide adsorbents by zeolitization of fly ash

Coal-combusting power plants are simultaneously among the main emitters of carbon dioxide and the main generator of solid by-products, such as fly ash (FA). An attempt to find a common solution for these environmental problems is reported in the present research work. This study describes a synthesis procedure for zeolite X by interaction of FA, originating from Bulgarian lignite coals with sodium hydroxide (NaOH), followed by hydrothermal treatment. The sorption capacity of the so-obtained zeolite with respect to carbon dioxide is estimated by using the thermogravimetric method. Ash residues, containing 52.66 mass% of SiO2 and 23.37 mass% of Al2O3, were subjected to a dual-stage fusion-hydrothermal conversion. Coal ash and NaOH mixture at a ratio of 1:2 was sintered at 550 °C, and after dilution with water under continuous stirring, the reaction mixture was charged into an autoclave for hydrothermal reaction occurring for 2 h at 90 °C. The obtained zeolite X was characterized by scanning electron microscopy and X-ray diffraction, and it was subjected to thermogravimetric analysis before and after exposure to carbon dioxide flow. Determination of its adsorption capacity toward CO2 was carried out at 22 °C, it was measured to be 60 mg g−1 at this temperature, and the adsorption–desorption equilibrium was reached after 1 h under flow conditions (30 mL min−1). The sorption capacity of fly ash-based zeolite was compared to that of a reference zeolite X, synthesized from pure starting materials.

Preparation and characterization of hydrotalcite-like materials from flyash for transesterification

In the present study, attempts were made to synthesize Mg–Al hydrotalcite-like materials with bifunctional properties from flyash and flyash-based zeolite by coprecipitation method. The synthesized hydrotalcite and their corresponding Mg–Al mixed oxides obtained after calcination were characterized for their structural, compositional, thermal, and morphological properties. The synthesized hydrotalcite had Mg/Al ranging from 1.3 to 2.3. The activity of the synthesized catalyst was estimated in transesterification of mustard oil, and the effects of reaction time, catalyst concentration, and methanol-to-oil molar ratio on biodiesel production were also investigated. A maximum yield of 93.4 % was obtained with methanol-to-oil molar ratio of 12:1, 7 wt% catalyst concentration for 6 h of reaction at 65 °C. The average value of activation energy of biodiesel in the conversion range of 0.2 < X < 0.9 was 130.5 kJ mol−1. This study showed the potential application of flyash and its use in modified Mg–Al hydrotalcite materials as heterogeneous catalysts in biodiesel production.

Synthesis, Characterization And Catalytic Activity Of Transition Metal Complexes Of Ascorbic Acid Encapsulated In Fly Ash Based Zeolite

A new route for the utilization of fly ash has been formulated. X-type zeolite has been synthesized from fly ash by alkali fusion followed by hydrothermal treatment. Ascorbic acid was used as a ligand for the synthesis of metal complexes of copper, nickel and vanadium encapsulated in the super cages of fly ash based zeolite (FAZ) by flexible ligand method and characterized by FTIR, XRD, Atomic Absorption Spectrometry (AAS), Ultra Violet–Visible spectroscopy and Thermo gravimetric analysis (TGA). The additional peaks corresponding to that of the complex have been observed which confirms the loading of the metal complexes in the zeolite cavities. The shifting of C=C-O stretching frequency found at 682 cm -1 in ascorbic acid to 601 cm -1 confirms the co-ordination of the ligand resulting in the formation of the metal complex. The thermo grams show deflation in three regions corresponding to the loss of the intra-zeolite water, metal complexes and the structural –OH group respectively. The catalytic activity of these complexes towards the liquid phase hydroxylation of phenol with hydrogen peroxide has been established. The extent of the reaction as a function of time has been investigated. Vanadium-ascorbate complex had the highest conversion of 78%. The product was identified as hydroquinol by GC-MS. This study reports a highly attractive catalytic method for the preparation of hydroquinol from phenol using aqueous hydrogen peroxide as the oxidising agent which is industrially significant.

Encapsulation of N,N-ethylenebis(salicylamide) Metal Complexes In Fly ash Based Zeolite, Characterization and Catalytic Activity

Coal fly ash has been used to synthesize X-type zeolite by alkali fusion followed by hydrothermal treatment. The synthesized fly ash based zeolite (FAZ) has been characterized by various analytical techniques. Copper(II), Nickel(II) and Zinc(II) complexes of N,N 1 -ethylenebis (salicylamide) encapsulated in the supercages of FAZ have been prepared by flexible ligand method and characterized by Fourier Transform infra red spectroscopy (FTIR), X-ray diffraction (XRD) analysis, Scanning electron microscopy (SEM), Atomic absorption spectrometry (AAS), Ultra Violet – Visible spectroscopy and Thermo gravimetric analysis (TGA). These complexes have been found to catalyze the liquid phase hydroxylation of phenol with hydrogen peroxide to yield catechol. It appears to be the first report of catalysis of metal complex encapsulated in fly ash based zeolite.

Fly ash based zeolite analogues: versatile materials for energy and environment conservation

Fly ash is combustion residue from burning of pulverised coal in electric utility generating stations. The annual production of fly ash in India is around 100 MTPA and is responsible for several environmental hazards, which is quite well documented. There are stringent norms for its land disposal and hence utilisation of fly ash is imperative. Fly ash has more than 85% of SiO2 and Al2O3 content and is therefore a tailor made raw material for production of zeolite. An innovative process has been developed for synthesis of zeolites using fly ash as a substitute for conventional raw materials viz. sodium silicate and aluminate. The process consists of three major steps viz. fusion of caustic soda and fly ash for optimal extraction of silicate and aluminate, aging step which provides time for formation of nuclei and hydrothermal crystallization resulting in activation of nuclei into well defined crystals. Low temperature operation, simplicity of process and optimal recycling of unused reactants and process water are special features of these processes. Zeolites have high internal and external surface areas and also exhibit high exchange capacities, which makes them versatile materials for targeting wide range of pollutants, ranging from cationic to anionic and hydrophilic to hydrophobic molecules. The major uses of zeolites are in adsorption, ion exchange and as catalysts. The use of zeolites in environmental remediation is restricted due to procurement problem and prohibitive cost, which can be overcome by using low cost fly ash based zeolites (FAZs). The synthesis of FAZ-A and FAZ-Y and their modifications either by transition metal incorporation or by surfactant treatment for various environmental applications in air, water and soil remediation are addressed in this review.

Application of model-free kinetics to the study of dehydration of fly ash-based zeolite

In the present paper, dehydration kinetics of zeolite Na-A synthesized from fly ash was investigated by means of thermogravimetric analysis. Na-A zeolite was formed from coal fly fash by fusion with sodium hydroxide and succeeding hydrothermal treatment at 100°C after induction period. The model-free kinetic method was applied to calculate the activation energy of the dehydration process of fly ash-based zeolite as a function of conversion and temperature. The Vyazovkin model-free kinetic method also enabled the definition of time, necessary to remove water molecules from the zeolite structure for a given temperature.