Effect of microwave irradiation on crystal growth of zeolitized coal fly ash with different solid/liquid ratios

Aldahri, Tahani; Behin, Jamshid; Kazemian, Hossein; Rohani, Sohrab

doi:10.1016/j.apt.2017.08.013

Cited by 33 publications

(18 citation statements)

References 48 publications

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“…A similar observation was seen with the complete microwave synthesis method ( Section 2.4 ). Aldahri et al, 31 synthesized zeolite-P with low crystallinity and low purity dominated by coal fly ash phases at 6 h conventional heating times. 31 While in this study, a shorter conventional heating time of 1 h resulted in the formation of highly crystalline zeolite A with little sodalite phases.…”

Section: Results and Discussionmentioning

confidence: 99%

Microwave Irradiation-Assisted Synthesis of Zeolites from Coal Fly Ash: An Optimization Study for a Sustainable and Efficient Production Process

et al. 2020

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Class F South African coal fly ash was used as a precursor for the synthesis of zeolite A via complete microwave irradiation. To attain optimal conditions for the synthesis of zeolite A with minimum impurities, the microwave synthesis time, irradiation power, and Si/Al ratio were varied. Sodalite with fly ash phases were obtained when the Si/Al ratio in the coal fly ash was not adjusted and when the microwave irradiated coal fly ash slurry was used instead of the extract solution. Increased microwave irradiation time power and time favored the crystallization of zeolite A phase due to sufficient energy needed to ensure the dissolution of Al and Si from coal fly ash. A Brunauer–Emmett–Teller surface area of 29.54 m 2 /g and a cation exchange capacity of 3.10 mequiv/g were achieved for zeolite A, suggesting its potential application as an adsorbent and cation exchange material for environmental remediation. Complete microwave irradiation offers a greener approach toward zeolite synthesis from coal fly ash compared to conventional hydrothermal and fusion methods that consume a lot of energy and require longer reaction times.

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Section: Results and Discussionmentioning

confidence: 99%

Microwave Irradiation-Assisted Synthesis of Zeolites from Coal Fly Ash: An Optimization Study for a Sustainable and Efficient Production Process

et al. 2020

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“…X‐ray diffraction (XRD, D/max‐2200PC, Bruker, Germany) using a D8 VENTURE diffractometer was employed to detect the crystal phase of the zeolites. The intensity of the peaks was computed using the “peak fitting” algorithm through Jade 5.0 software and the relative crystallinity of the samples was calculated by the expression shown in Equation (), where S sample is the area of all NaP characteristic peaks in the sample product and S standard is the area of all characteristic peaks of NaP zeolite synthesized with analytical grade Na 2 SiO 3 and NaAlO 2 . Scanning electron microscopy (SEM, JSM‐6510LV JEOL, Japan) was carried out to observe grain morphology.…”

Section: Methodsmentioning

confidence: 99%

In‐situ synthesis of NaP zeolite doped with transition metals using fly ash

et al. 2019

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Here, a novel approach has been proposed to synthesize NaP zeolite adsorbents doped with transition metals (M‐NaP) using the Na2SiO3 and NaAlO2 compounds extracted from fly ash via activation and stage treatment. The preparation process of M‐NaP employed the in‐situ synthesis in combination with organic complexation method. The effects of the addition amounts and valence state of transition metals on the zeolite products were investigated. The crystalline phase, morphology, and particle size of M‐NaP were characterized using X‐ray diffractometry (XRD), Scanning electron microscopy (SEM), and Laser particle size analyzer (PSD). The doping process was investigated using X‐ray photoelectron spectroscopy (XPS) and Materials Studio. The adsorption performance of M‐NaP was tested by the adsorption of Zn2+. The optimal molar ratio of n(Al2O3)/n(M) was identified as 8:1 for Co–NaP, Ni–NaP, and Fe–NaP, compared with 6:1 for Ti–NaP. The influence of transition metals on adsorption was: Co–NaP > Ni–NaP > Ti–NaP > Fe‐NaP. Due to largest surface area of Co–NaP (162.5 m2/g, five times than that of NaP‐RAW), the maximum removal rate of Zn2+ was above 99.50% at 25°C. The existence state of transition metals in M‐NaP primarily included: isomorphous substitution and balance of the skeletal charge, with the latter in majority. The simulation of Materials Studio indicates that Si at T4 was first substituted and then, Si at T3 opposite T4 was replaced when the replacement of Si in different sites occurred.

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“…e change in hemihydrate gypsum unit cell parameters reflects the change in the crystal growth environment [16,17]. Due to the nonthermal effect of microwaves [18,19], aluminum and sulfate ions are more easily combined than they are during normal heating; therefore, aluminum ions are doped during the growth process. e mechanism of aluminum ion crystal transformation under microwave irradiation involves the combination of aluminum ions and sulfate radicals changing the crystal morphology of calcium sulfate hemihydrate, which is different from the crystal transformation mechanism under conventional heating [15].…”

Section: Mechanism Of the Effect Of A Single Doping Ratio Of 5 MM Aluminum Ions On The Growth Of α-Calcium Sulfate Hemihydrate Crystalsmentioning

confidence: 99%

Effect of Aluminum Sulfate and Succinic Acid on the Growth Law of α‐Calcium Sulfate Hemihydrate under Microwave Irradiation

Feng

Guo

Lin

2021

Advances in Materials Science and Engineering

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The existing α-hemihydrate gypsum preparation process has low production efficiency and high energy consumption. In this paper, α-type hemihydrate gypsum was prepared by microwave irradiation using phosphogypsum as the raw material, calcium chloride solution as the reaction medium, and succinic acid and aluminum sulfate as crystal-transforming agents. Both aluminum sulfate and succinic acid were studied to determine the mechanism influencing the effect on the growth of α-type hemihydrate gypsum crystals. This study found that, without added succinic acid or aluminum ions, the crystal transformation rate of α-calcium sulfate hemihydrate reached 96% with the average length-diameter ratio reaching 21 after 1 h; when the dosage of succinic acid was 0.02%, the crystal transformation rate of α-calcium sulfate hemihydrate reached 96% with the average length-diameter ratio reaching 1.5 after 1.5 h; and when the aluminum ion dosage was 5 mM, the crystal transformation rate of α-calcium sulfate hemihydrate reached 97% with the average length-diameter ratio reaching 12.3 after 1 h. In addition, it was discovered that the reaction time was significantly shortened under microwave irradiation, and with an increase in succinic acid content, the regulation of the microscopic morphology of the calcium sulfate hemihydrate crystals was continuously enhanced and the aspect ratio of the crystals was continuously reduced. The EDS and Fourier transform infrared spectroscopy (FTIR) analysis showed that succinic acid did not adsorb onto the hemihydrate gypsum crystal during the reaction under microwave irradiation. The X-ray photoelectron spectroscopy (XPS) analysis revealed that aluminum ions affected crystal growth by incorporating into calcium sulfate hemihydrate crystals after reacting with sulfate radicals.

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Effect of microwave irradiation on crystal growth of zeolitized coal fly ash with different solid/liquid ratios

Cited by 33 publications

References 48 publications

Microwave Irradiation-Assisted Synthesis of Zeolites from Coal Fly Ash: An Optimization Study for a Sustainable and Efficient Production Process

Microwave Irradiation-Assisted Synthesis of Zeolites from Coal Fly Ash: An Optimization Study for a Sustainable and Efficient Production Process

In‐situ synthesis of NaP zeolite doped with transition metals using fly ash

Effect of Aluminum Sulfate and Succinic Acid on the Growth Law of α‐Calcium Sulfate Hemihydrate under Microwave Irradiation

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