Next Article in Journal
Nano-Phytoremediation of Heavy Metals Contaminated Wastewater Ecosystems and Wetlands by Constructed Wetlands Planted with Waterlogging-Tolerant Mycorrhizal Fungi and Vetiver Grass
Previous Article in Journal
Spectral Response (VNIR-SWIR) Associated with the Octahedral Sheet of Smectites
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Proceeding Paper

Siliceous Fly Ash Utilization Conditions for Zeolite Synthesis †

Department of Industrial Chemistry, Faculty of Natural Sciences, University of Tirana, 1000 Tirana, Albania
Department of Chemistry, Faculty of Natural Sciences, University of Tirana, 1000 Tirana, Albania
Istituto di Cristallografia, Consiglio Nazionale delle Ricerche, 70126 Bari, Italy
Institute of Methodologies for Environmental Analysis—IMAA-CNR, 85050 Tito Scalo Potenza, Italy
Authors to whom correspondence should be addressed.
Presented at the 2nd International Electronic Conference on Mineral Science, 1–15 March 2021; Available online:
Environ. Sci. Proc. 2021, 6(1), 24;
Published: 25 February 2021
(This article belongs to the Proceedings of The 2nd International Electronic Conference on Mineral Science)


Fly ash is a coal combustion product partly disposed of in landfills since it finds no other application. Recycling this solid is of great benefit in terms of quality, cost effectiveness and the environment. The chemical and mineralogical composition of siliceous fly ash makes it an attractive and economic raw material for the synthesis of zeolites. Zeolites are microporous, aluminosilicate minerals characterized by a three-dimensional network of tetrahedral units produced industrially on a large scale. In this work, synthetic X and A-type zeolite with high crystallinity and high value of surface area were synthesized by a pre-fusion method followed by a hydrothermal treatment under various conditions. The data indicate that zeolitic products were obtained using NaOH while no zeolitic material was crystallized using KOH and LiOH. Pre-treatment of fly ash with acid before being used in the synthesis of artificial zeolites is considered an important parameter for the purity phase of zeolites. Without sodium aluminate additions, synthetic zeolite A was not formed. The results confirm that temperature, crystallization time, SiO2/Al2O3 ratio and type of water (distilled water and seawater) are also important parameters influencing type of zeolite synthesized. Zeolite X was used as a novel catalyst for the alkylation of phenol using diethyl carbonate.

1. Introduction

The major generators of industrial solid wastes are the by-products of combustion power plants producing coal fly ash. In the last few decades, worldwide coal consumption has been monitored. The main producer being China, followed by India, United States and Russia [1]. Accumulation of massive amounts of such residues, if not managed properly, causes serious environmental, aesthetic, economic and social problems. The re-evaluation of “wastes”, in which significant energy has been invested and lost through disposal, via their conversion into sustainable construction materials and products, is probably the best way to recover this energy [2].
Fly ash is one of the waste by-products with major potential for recycling. To date, several approaches have been carried out aiming to increase the utilization of fly ash and reducing its negative impacts. Fly ash offers a large spectrum of utilization possibilities ranging from underground mining to the building and cement industry [3,4]. Furthermore, the synthesis of mesoporous silica from fly ash has attracted interest due to the resulting material’s characteristics [5].
Fly ash is mineralogically characterized by the presence of amorphous materials and the mixture of ferro-aluminosilicate minerals. The high content of silica and alumina makes it a suitable raw material for the synthesis of high value zeolitic material.
Since the last millennium, zeolites have been known as a “magic rock”. Zeolites are hydrated aluminosilicate minerals with a three-dimensional open structure. They consist of SiO4 and AlO4 tetrahedra which gives it an anionic framework with the negative charge of Al being compensated by extra framework cations (positively charged ions), some being Na+, K+, Ca2+, Mg2+ and water molecules. The porous structure is large enough to be able to accommodate the guest ionic and molecular species. It is also possible to produce zeolite structures that do not appear in nature. Therefore, converting fly ash into zeolite is expected to resolve the problem of the disposal of fly ash, at least partially, and thereby minimize its impact on the environment.
In the last decade, fly ash was used as a raw material for obtaining zeolites type X [6,7], A [6,7,8,9] and P [10], competing with zeolites made from pure industrial chemicals, which is of great importance for sustainable resource management [11]. Developing green techniques with cost-effective and eco-friendly routes for the synthesis of zeolite from FA is very significant for the economy and sustainable technology. Furthermore, the synthesis of zeolite from fly ash has attracted interest due to the resulting material’s characteristics [12,13].
Two well-known methods are commonly applied, namely the conventional hydrothermal method using an alkaline medium, and the hydrothermal process with fusion pre-treatment at high temperatures. The advantages of the fusion method are its speed of reaction [14], and the purity of the final product [15] whereas the hydrothermal method has an advantage in terms of the consistent pattern of zeolite produced. Synthesis conditions for each of the methods are different; they include pretreatment with acid [8], various alkali sources [16], molarities of alkaline agents [17], solution–solid ratio [18], temperature [6], reaction time [19], pressure, type of incubation [20] and type of water [21,22].
In this project, different conditions determining the synthesis of zeolites from fly ash were investigated. The synthetic products were characterized in terms of mineralogy and morphology.

2. Materials and Methods

2.1. Materials

The main raw material, coal fly ash (Class F type) sample, was supplied from the BauMineral GmbH, a German power plant company. Sodium hydroxide anhydrous pellets with ≥97.0% purity, sodium aluminate 99.9% NaAlO2 powder and hydrochloric acid ACS reagent 37% HCl were purchased from Sigma-Aldrich.

2.2. Zeolite Synthesis Procedure

Initially raw fly ash (FA) was added to HCl, with 20% w/w acid concentration under the acid/FA ratios of 15 mL acid/g FA [8]. The mixture was constantly stirred at the rate of 300 rpm at 80 °C for 2 h. Once stirred, the solid sample was filtered and repeatedly washed with distilled water until the solution reached neutral pH and then dried overnight at 90 °C in oven. The fly ash was mixed with sodium hydroxide anhydrous pellets, in a weight ratio NaOH/FA of 0.75 and 1.25 by initially grinding the fly ash with sodium hydroxide. Subsequently, the mixture was fused at 550 °C for 1 h in a muffle furnace. Once cooled down, the product was crushed and was added to NaAlO2 to make the ratio NaAlO2/FA of 0.5 and 1. To investigate the effect of the ratio of Si/Al the mixture was dispersed in a weight ratio of 1/5 mL of seawater or distilled water. Crystallization was then performed under static conditions (40, 60 and 90 °C) for 1–72 h. The crystal products were separated and washed several times with distilled water for a pH of around 10–11. The wet solid was finally dried overnight at 105 °C and then calcined at 550 °C for 5 h and used as previously described.

2.3. Characterization Methods

The X-ray fluorescence (XRF) (PANalytical AXIOS Spectrometer) was applied for the chemical composition of major chemical constituents and trace elements. The mineral characterizations of both fly ash and zeolite products were determined by powder X-ray diffraction (XRD) using a Philips X’Pert vertical diffractometer, using cooper radiation Cu-Kα. The morphology and the chemical composition of the main mineral components were determined using electron scanning microscope (SEM). The equipment used was a Zeiss Supra 40 scanning microscope. The specific surface area of the zeolite samples was determined applying N2 adsorption—desorption technique involving Brunauer–Emmett–Teller (BET), using a Sorpty 1750 Fison instrument, after a preliminary degassing step under vacuum at 150 °C.

3. Results

The chemical composition of fly ash determined by means of X-ray fluorescence (XRF) contains mainly 78 % SiO2 + Al2O3, whereas the impurities consist of metallic oxides such as Fe2O3 and CaO. Other elements including K2O, TiO2, SO3 and MgO are present in trace amounts, shown in Table 1 (defined as class F coal fly ash corresponding with ASTM C618). Fly ash was treated with acid washing to dealuminate and reduce the concentration of iron and alkali oxides and to enhance Si and Al compositions. XRF data (Table 1) indicate that most of the impurities (Fe2O3, CaO, and other impurities) were removed by FA treatment with 20% w/w of hydrochloric acid in liquid ratio (acid/fly ash solution of 15 mL acid/1 g FA) thus enhancing SiO2 + Al2O3 compositions. Table 1 shows that the amount of silicon was increased by acid treatment, thus increasing the mass ratio of SiO2/Al2O3 which was 1.8% before acid treatment and became 2.25% after treatment. This is also confirmed by XRD data (Figure 1) which mainly confirms the presence of amorphous phase by giving wide elevations in the 2θ range of 20–35°. Meanwhile the main crystalline phase consists largely of quartz (SiO2) (Ref. 01-089-8936) and mullite (Al6Si2O13) (Ref. 00-015-0776) where sharp points are observed.
The SEM image in Figure 1 shows the typical fly ash morphology characterized by the most spherical particles which consist of cenospheres and plerospheres. XRD data in Figure 1 indicate that the mineral composition of fly ash does not change following the acid treatment showing the presence of mullite and quartz, as well as a large number of amorphous materials. The specific surface, instead, slightly increases after the treatment with acid, from 1.5 m2/g to 2.9 m2/g. Figure 1 also displays the XRD pattern of FA after fusion at 550 °C for 1 h with NaOH. The profile indicates the formation of sodium silicate (Na2SiO3) (Ref. 00-016-0818) and silicon oxide dealuminate (Al2SiO5) (Ref. 01-088-0890).
On the other hand, these newly formed compounds dissolve in water much more easily than quartz and mullite in the initial FA. Dissolution of FA and alkaline aluminosilicate phases released ionic species which were activated at the nucleation sites. As condensation of aluminum and silicon ions occurred, the surface of the FA particles was covered with the precipitate of an aluminosilicate gel. After some time, the zeolite phases were crystallized, using NaOH as an activator. All zeolite products were obtained when NaOH was used as an activator (Figure 2a) whereas no zeolite material was crystallized using KOH or LiOH (Figure 2b,c).
XRD data show the presence of an amorphous geopolymer phase in the sample treated with KOH as activator (Figure 2b); and lithium silicate (Li2SiO3) when LiOH was used (Figure 2c). Figure 3 shows A- and X-type zeolites after NaOH pre-fusion treatment followed by the hydrothermal process. In detail, X-type zeolite (Figure 3, top) formed after FA was pre-treated with hydrochloric acid followed by the fusion process at 550 °C for 1 h (NaOH)/FA = 1.25), with a crystallization temperature 60 °C, crystallization time of 72 h and distilled water as the solution. In detail, the X-ray diffraction pattern shows that the generated X zeolite has a high crystallinity and is pure phase. The surface area (BET) for this synthetic product was 412 m2/g. The diffraction peaks of the powder pattern are well described by Na71(Si121Al71)O384 crystal structure (Ref. 00-150-7214).
The addition of sodium aluminate (NaAlO2/FA = 1.0) combined with a higher crystallization temperature (90 °C) and higher incubation time (6 h) determined the formation of A-type (Figure 3 bottom). Zeolite A was synthesized using the following experimental conditions: FA pre-treated with hydrochloric acid (HCl) followed by the fusion process at 550 °C for 1 h (NaOH/FA = 1.25), the addition after calcination of sodium aluminate at the ratio NaAlO2/FA = 1, the crystallization temperature at 90 °C and a crystallization time of 6 h using distilled water as the solution in 1/5 solid/liquid ratio. The XRD model shows that zeolite A is characterized by a very high crystallinity phase (80–97%) with yield up to 71%. However, the results show that the surface area of this zeolite is 30 m2/g (BET) much lower than X-type zeolite. The diffraction peaks of the powder pattern are well described by Na12(Al12Si12O48)(H2O)27 crystal structure (Ref. 00-8104-214).
Both zeolite X and zeolite A belong to the cubic system. Synthesis conditions strongly influenced the morphology of the synthesis products. Figure 4a shows an SEM micrograph of typical octahedral crystals of zeolites X (Figure 4a) and cubic shapes of zeolite A (Figure 4b).
Zeolite have been successfully synthesized from fused fly ash by using seawater as a crystallization medium. Using distilled water, zeolite type X with a specific surface area of 412 m2/g was formed; meanwhile, when sea water was used this created zeolite type X with a lower specific surface area of 362 m2/g.

4. Discussion and Conclusions

Zeolite samples were synthesized from fly ash through fusion followed by hydrothermal treatment. FA contained a reasonable fraction of Si and Al, which is considered a potential raw material for the synthesis of zeolite. Several other components act as poison during the catalytic applications of zeolites [19]. Fly ash particles are mostly spherical in shape with a relatively smooth surface structure. Cenospheres show a large variation in their dimensions and plerospheres expose smaller spheres [22]. Fly ash was treated with acid washing to dealuminate and reduce the concentration of iron and alkali oxides. Results agree with those of [7,8], who reported that heavy metals show a high leachability in acid condition. Fe2O3 is closely bound to ash and does not break down easily, while the CaO content in FA is highly soluble and purifies more than half of the content, specifically, CaO was 4.2% before acid treatment and reached 1.1% after acid treatment. The untreated carbon fly ash had a purity of 79% (Na2O, SiO2 and Al2O3), while the HCl treatment provided a purity of the material of up to 87% (Na2O, SiO2 and Al2O3). From the results it is observed that the acid pre-treatment of the fly ash before being used in the synthesis of artificial zeolites is considered an important parameter for the purity of the zeolite phase.
Conversion of FA to zeolite materials using an alkaline fusion, followed by hydrothermal treatment revealed that KOH and LiOH showed a poor efficiency to activate FA, compared to the case where NaOH was used as activator as reported by [23]. Na+ cations also play a very important role during zeolitization because they stabilize the sub-building units of zeolite frames and are fundamental to the synthesis of zeolite under hydrothermal conditions [19]. On the other hand, K+ solution promotes the slow rate of crystallization in KOH solutions and is therefore the suppression factor for zeolite synthesis [24]. The synthesis of zeolite X was favored by the value 1.7 of the mass ratio SiO2/Al2O3, otherwise expressed in the molar ratio of 2.9, which is suitable for the synthesis of zeolite X. These results agree with those of [25] who reported that zeolites such as (Na-X, Na-Y) formed in the Si/Al molar ratio of more than 1; in this case the concrete molar ratio Si/Al was 1.35. The synthesis of zeolite A is attributed to the modified Si/Al ratio with the addition of NaAlO2 which enables the synthesis of zeolites A instead of zeolites X. It is worth mentioning here that the synthesis of type A zeolite requires much shorter crystallization time (starting from 4 h compared to the synthesis of type X zeolites which requires 72 h). The Si/Al molar ratio for the synthesized zeolite A is calculated at 0.98, this agrees with [25] who reported also that zeolites A are formed in the Si/Al molar ratio around the value 1.
Meanwhile, crystallization is the process that forms the crystal framework of the zeolite, which occurs faster at higher crystallization temperatures such as 90 °C, but the highest phase purity is obtained at 60 °C. The crystallinity of zeolite X increases progressively in the crystallization temperature range from 40 °C to 60 °C. The surface area increased from 44 to 412 m2/g as the crystallization temperature increased from 40 to 60 °C, and then dropped to 318 m2/g at 90 °C. The use of seawater improves the zeolite synthesis, and the action is more pronounced at lower incubation temperatures. When sea water is used instead of distilled water to produce X-type zeolite, the newly formed mineral has lower purity and specific surface area but higher catalytic activity than when distilled water is used [12].
With a short crystallization time of 24 h, low temperature at 60 °C and low ratio of NaOH/FA 0.75, the use of sea water was favorable compared to distilled water in the synthesis of zeolite type X.
However, it was confirmed from the XRD profile, that when sea water was used, with a crystallization time of 72 h, a crystallization temperature of 90 °C and a ratio of NaOH/FA 1.25, sodalite was generated together with an undesired secondary.
Synthetic zeolites were tested as heterogeneous basic catalysts in the gas-phase alkylation of phenol with diethyl carbonate (DEC). This obtained phenol conversions up to 95% with a selectivity to phenetole higher than 85%, thus demonstrating that the catalytic activity of the zeolites synthesized from fly ash is very high.
Results obtained show that the method described is clean, cost-effective, and environmentally friendly. The stability of the catalyst and the applicability of our innovative synthetic zeolites for catalytic application as heterogeneous basic systems makes zeolite synthesis from FA an alternative for the common commercial catalysts used in industries.

Author Contributions

Conceptualization, A.K. and S.G.; methodology, C.B.; software, D.S.; formal analysis, V.T.; investigation, C.B.; data curation, C.B. and D.S.; writing—original draft preparation, S.G.; writing—review and editing, C.B.; supervision, A.K. All authors have read and agreed to the published version of the manuscript.


This research was funded by Erasmus Mundus SUNBEAM Scholarship Programme, grant number SUNB1500545.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.


We thank the support offered by Cavani F. and Tabanelli T. from the “Department of Industrial Chemistry “Toso Montanari” Alma Mater Studiourum University of Bologna” Italy on different techniques of characterization of zeolites. We also thank the company Bau Mineral GmbH for the cooperation for collecting fly ash for this research.

Conflicts of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


  1. Global Energy Statistical Yearbook 2020. Available online: (accessed on 12 October 2020).
  2. Goumans, J.J.J.M.; van der Sloot, H.A.; Aalbers, T.G. (Eds.) Waste Materials in Construction, 1st ed.; Studies in Environmental Science; Elsevier Science Publishers: Amsterdam, The Netherlands, 1991; Volume 48, ISBN 9780080875071. [Google Scholar]
  3. Shen, D.; Wang, W.; Li, Q.; Yao, P.; Jiang, G. Early age behavior and cracking potential of fly ash concrete under restrained condition, Mag. Conc. Res. 2020, 72, 246–261. [Google Scholar] [CrossRef]
  4. Korpa, A.; Kota, T.; Spahiu, E.; Trettin, R. An innovative approach for producing high volume fly ash blended cements that meet European standard requirements by employing a silicious coal fly ash exhibiting unusually high water demand and other peculiar properties. Zaštita materijala 2013, 54, 334–340. [Google Scholar]
  5. Miricioiu, M.G.; Niculescu, V.-C. Fly Ash, from Recycling to Potential Raw Material for Mesoporous Silica Synthesis. Nanomaterials 2020, 10, 474. [Google Scholar] [CrossRef]
  6. Belviso, C.; Cavalcante, F.; Huertas, F.J.; Lettino, A.; Ragone, P. The crystallisation of zeolite (X- and A-type) from fly ash at 25 °C in artificial sea water. Micropor. Mesopor. Mat. 2012, 162, 115–121. [Google Scholar] [CrossRef]
  7. Ruen-ngam, D.; Rungsuk, D.; Apiratikul, R.; Pavasant, P. Zeolite formation from coal fly ash and its adsorption potential. J. Air Waste Manag. Assoc. 2009, 59, 1140–1147. [Google Scholar] [CrossRef] [PubMed]
  8. Panitchakarn, P.; Laosiripojana, N.; Viriya-umpikul, N.; Pavasant, P. Synthesis of high-purity Na-A and Na-X zeolite from coal fly ash. J. Air Waste Manag. Assoc. 2014, 64, 586–596. [Google Scholar] [CrossRef]
  9. Soe, J.T.; Kim, S.S.; Lee, Y.R.; Ahn, J.W.; Ahn, W.S. CO2 capture and Ca2+ exchange using Zeolite A and 13X prepared from power plant fly ash. Bull. Korean Chem. Soc. 2016, 37, 490–493. [Google Scholar] [CrossRef]
  10. Behin, J.; Bukhari, S.S.; Kazemian, H.; Rohani, S. Developing a zero liquid discharge process for zeolitization of coal fly ash to synthetic NaP zeolite. Fuel 2016, 171, 195–202. [Google Scholar] [CrossRef]
  11. Hums, E. Synthesis of Phase-Pure Zeolite Sodalite from Clear Solution Extracted from Coal Fly Ash. J. Thermodyn. Catal. 2017, 8, 187. [Google Scholar] [CrossRef]
  12. Gjyli, S.; Korpa, A.; Tabanelli, T.; Trettin, R.; Cavani, F.; Belviso, C. Higher conversion rate of phenol alkylation by using synthetic fly ash-based zeolites. Microporous Mesoporous Mat. 2019, 284, 434–444. [Google Scholar] [CrossRef]
  13. Manzano, M.; Vallet-Regi, M. Mesoporous silica nanoparticles in nanomedicine applications. J. Mater. Sci. Mater. 2018, 29, 65. [Google Scholar] [CrossRef]
  14. Querol, X.; Moreno, N.; Umana, J.C.; Alastuey, A.; Hernandez, E.; López-Soller, A.; Plana, F. Synthesis of zeolite from coal fly ash: An overview. Int. J. Coal Geol. 2002, 50, 413–423. [Google Scholar] [CrossRef]
  15. Rayalu, S.J.; Udhoji, N.K.; Munshi, Z.M.; Hasan, J. Highly crystalline zeolite-A from fly ash of bituminous and lignite coal combustion. J. Hazard. Mater. 2001, 88, 107–121. [Google Scholar] [CrossRef]
  16. Wajima, T.; Ishimoto, H.; Kuzawa, K.; Ito, K.; Tamada, O.; Gunter, M.E.; Rakovan, J.F. Material conversion from paper-sludge ash in NaOH, KOH, and LiOH solutions. Am. Miner. 2007, 92, 1105–1111. [Google Scholar] [CrossRef]
  17. Wang, C.F.; Li, J.S.; Wang, L.J.; Sun, X.Y. Influence of NaOH concentrations on synthesis of pure-form zeolite A from fly ash using two-stage method. J. Hazard. Mater. 2008, 155, 58–64. [Google Scholar] [CrossRef] [PubMed]
  18. Vucinic, D.; Miljanovic, I.; Rosic, A.; Lazic, P. Effect of Na2O/SiO2 mole ratio on the crystal type of zeolite synthesized from coal fly ash. J. Serb. Chem. Soc. 2003, 68, 471–478. [Google Scholar] [CrossRef]
  19. Ojha, K.; Pradhan, N.C.; Samanta, A.N. Zeolite from fly ash: Synthesis and characterization. Bull. Mater. Sci. 2004, 27, 555–564. [Google Scholar] [CrossRef]
  20. Tanaka, H.; Fujii, A. Effect of stirring on the dissolution of coal fly ash and synthesis of pure-form Na-A and -X zeolites by two-step process. Adv. Powder Technol. 2009, 20, 473–479. [Google Scholar] [CrossRef]
  21. Yu, Y.; Li, X.; Zou, X.; Zhu, X. Effect of seawater salinity on the synthesis of zeolite from coal fly ash. Front. Environ. Sci. Eng. 2014, 8, 54–61. [Google Scholar] [CrossRef]
  22. Belviso, C.; Cavalcante, F.; Fiore, S. Synthesis of zeolite from Italian coal fly ash. Differences in crystallization temperature using seawater instead of distilled water. Waste Manag. 2010, 30, 839–847. [Google Scholar] [CrossRef]
  23. Shivpuri, K.K.; Lokeshappa, B.; Kulkarni, D.A.; Dikshit, A.K. Metal leaching potential in coal fly ash. Am. J. Environ. Eng. 2011, 1, 21–27. [Google Scholar] [CrossRef]
  24. Murayama, N.; Yamamoto, H.; Shibata, J. Zeolite synthesis from coal fly ash by hydrothermal reaction using various alkali sources. J. Chem. Technol. Biotechnol. 2002, 77, 280–286. [Google Scholar] [CrossRef]
  25. Tanaka, H.; Sakai, Y.; Hino, R. Formation of Na-A and -X zeolites from waste solutions in conversion of coal fly ash to zeolites. Mater. Res. Bull. 2002, 37, 1873–1884. [Google Scholar] [CrossRef]
Figure 1. X-ray diffraction patterns of raw fly ash, fly ash pretreated with acid, fly ash pretreated with acid and fused with NaOH/FA 1.25 at 550 °C for 1 h. Top right, Scanning electron microscopy image of raw fly ash.
Figure 1. X-ray diffraction patterns of raw fly ash, fly ash pretreated with acid, fly ash pretreated with acid and fused with NaOH/FA 1.25 at 550 °C for 1 h. Top right, Scanning electron microscopy image of raw fly ash.
Environsciproc 06 00024 g001
Figure 2. X-ray diffraction patterns of products synthesized from fly ash using as an activator: (a) NaOH; (b) KOH; and (c) LiOH.
Figure 2. X-ray diffraction patterns of products synthesized from fly ash using as an activator: (a) NaOH; (b) KOH; and (c) LiOH.
Environsciproc 06 00024 g002
Figure 3. X-ray diffraction patterns of synthesized zeolite from fly ash type Zeolite X (top) and Zeolite A (bottom).
Figure 3. X-ray diffraction patterns of synthesized zeolite from fly ash type Zeolite X (top) and Zeolite A (bottom).
Environsciproc 06 00024 g003
Figure 4. Scanning electron microscopy (SEM) images of (a), zeolite type X (b), zeolite type A.
Figure 4. Scanning electron microscopy (SEM) images of (a), zeolite type X (b), zeolite type A.
Environsciproc 06 00024 g004
Table 1. Chemical composition of raw and acid-treated fly ash analyzed by XRF.
Table 1. Chemical composition of raw and acid-treated fly ash analyzed by XRF.
Chemical Composition (wt. %)Fly Ash RawFly Ash Acid Treatment
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Gjyli, S.; Korpa, A.; Teneqja, V.; Siliqi, D.; Belviso, C. Siliceous Fly Ash Utilization Conditions for Zeolite Synthesis. Environ. Sci. Proc. 2021, 6, 24.

AMA Style

Gjyli S, Korpa A, Teneqja V, Siliqi D, Belviso C. Siliceous Fly Ash Utilization Conditions for Zeolite Synthesis. Environmental Sciences Proceedings. 2021; 6(1):24.

Chicago/Turabian Style

Gjyli, Silvana, Arjan Korpa, Valdet Teneqja, Dritan Siliqi, and Claudia Belviso. 2021. "Siliceous Fly Ash Utilization Conditions for Zeolite Synthesis" Environmental Sciences Proceedings 6, no. 1: 24.

Article Metrics

Back to TopTop