On the state of the art of crystalline structure reconstruction of coal fly ash: A focus on zeolites

Ju, Tongyao; Meng, Yuan; Han, Shuangfeng; Li, Lin; Jiang, Jianguo

doi:10.1016/j.chemosphere.2021.131010

Cited by 46 publications

(21 citation statements)

References 115 publications

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“…This study produced near-pure zeolite products at 150 °C, given that halite can be easily removed by washing. The REE leaching experiment using citrate might serve as a pretreatment process to remove nonreactive phases (such as hematite, lime, and periclase) (Figure ) prior to hydrothermal synthesis and thus resulted in the high purity of zeolite in this study . Importantly, as all CFA solid residues are converted to zeolite, no solid waste will be produced from this system from a perspective of solid waste management.…”

Section: Resultsmentioning

confidence: 99%

“…The REE leaching experiment using citrate might serve as a pretreatment process to remove nonreactive phases (such as hematite, lime, and periclase) ( Figure 1 ) prior to hydrothermal synthesis and thus resulted in the high purity of zeolite in this study. 57 Importantly, as all CFA solid residues are converted to zeolite, no solid waste will be produced from this system from a perspective of solid waste management. Wastewater from zeolite synthesis could be reused to minimize wastewater production ( Figure S12 ).…”

Section: Resultsmentioning

confidence: 99%

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Green Approach for Rare Earth Element (REE) Recovery from Coal Fly Ash

Liu

Zhao

Xie

et al. 2023

Environ. Sci. Technol.

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Due to the growing demands of rare earth elements (REEs) and the vulnerability of REEs to potential supply disruption, there have been increasing interests in recovering REEs from waste streams such as coal fly ash (CFA). Meanwhile, CFA as a large industrial waste stream in the United States (U.S.) poses significant environmental and economic burdens. Recovery of REEs from CFA is a promising solution to the REE scarcity issue and also brings opportunities for CFA management. This study demonstrates a green system for REE recovery from Class F and C CFA that consists of three modules: REE leaching using citrate, REE separation and concentration using oxalate, and zeolite synthesis using secondary wastes from Modules I and II. In Module I, ∼10 and 60% REEs were leached from the Class F and C CFA samples, respectively, using citrate at pH 4. In Module II, the addition of oxalate selectively precipitated and concentrated REEs from the leachate via the formation of weddellite (CaC 2 O 4 •2H 2 O), while other trace metals remained in solution. In Module III, zeolite was synthesized using wastes from Modules I and II. This study is characterized by the successful recovery of REEs and upcycling of secondary wastes, which addresses both REE recovery and CFA management challenges.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Green Approach for Rare Earth Element (REE) Recovery from Coal Fly Ash

Liu

Zhao

Xie

et al. 2023

Environ. Sci. Technol.

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“…The growth rate of the crystal becomes slow, and finally close to zero, reaching a new dynamic equilibrium, that is, the end of crystal growth. [36,37] At this final stage, [38] the topological structure of eight-membered ring two-dimensional channel (GIS) cube skeleton is formed, as shown in the processes (d) to (e) of Figure 6.…”

Section: Chemistryselect Slope Of Crystallinity Time Vs Relative Crys...mentioning

confidence: 99%

Synthesis of a Coal Fly Ash‐Based NaP Zeolite Using the Microwave‐Ultrasonic Assisted Method: Preparation, Growth Mechanism, and Kinetics

et al. 2023

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Fly ash was used as the raw material to prepare coal fly ash‐based NaP zeolite using the microwave‐ultrasonic‐hydrothermal method. The obtained NaP zeolite has a completed crystal structure, regular surface morphology, uniform particle size (about 1.6 um), large specific surface area (48.85 m2/g) and good thermal stability. Under microwave and ultrasonic external fields, the coal fly ash‐based NaP zeolite crystals grow in an S‐shape, achieving single crystal growth and uniform crystal growth size. The activation energy of NaP zeolite crystal growth Ea is 2.08 kJ/mol, the pre‐exponential factor A is 85.63.

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“…In hydrothermal situations, the water molecules move faster, which increases the ionization products constantly and the coefficient of diffusion, thus facilitating the chemical reaction. Recently, hydrothermal treatment (HT) has become an effective technology because of its ability to utilize aluminum or silicon sources in fly ash at lower temperatures (150–200 °C) or by adding external aluminum and silicon; fly ash is converted to zeolites, katazite, solids, and other materials while immobilizing hazardous heavy metals in the final product. − These silicate minerals, which are like zeolite, have remarkable adsorption capacity and cation exchange capacity (CEC), are thermally stable, and can effectively stabilize heavy metals in hydrothermal processes. Therefore, they are collectively referred to as zeolite minerals or zeolite media. ,,, Conversely, the traditional hydrothermal treatment method may have drawbacks, such as a sluggish reaction rate and low energy conversion efficiency, when producing zeolite-like crystals from fly ash. ,, Jin et al determined that after conventional hydrothermal treatment, the zeolite-like minerals generated stabilized heavy metals by precipitation, physical encapsulation, ionic adsorption, and ion exchange, leading to a stabilization efficiency of more than 95% for heavy metals.…”

Section: Treatment and Disposal Of Heavy Metals In Fly Ashmentioning

confidence: 99%

Advances and Outlook of Heavy Metal Treatment Technology from Municipal Solid Waste Incineration Fly Ash: A Review

Xiao,

Huang,

Cheng

et al. 2023

Energy Fuels

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With the global industrialization process and socioeconomic development, the amount of municipal solid waste (MSW) generated is growing significantly. With the growth trend of municipal solid waste, incineration is widely used for waste treatment but produces a large amount of municipal solid waste incineration fly ash, which contains heavy metals that can seriously harm human health and the ecological environment. In this Review, the current situation of MSWI fly ash disposal is reviewed, and the technologies for harmless disposal and resource utilization of heavy metals in MSWI fly ash are summarized, including solidification stabilization, leaching extraction, heat treatment, combination methods, etc. We meticulously summarized the recent progress of various incineration fly ash disposal technologies, analyzed the difficulties and solutions in formulating various feasible technical strategies, and compared their potential in the safe, environmentally friendly, and economical utilization of MSW fly ash resources. Furthermore, we also provide an outlook on the potential challenges and prospects of future progress in the harmless disposal and resource recycling of fly ash.

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On the state of the art of crystalline structure reconstruction of coal fly ash: A focus on zeolites

Cited by 46 publications

References 115 publications

Green Approach for Rare Earth Element (REE) Recovery from Coal Fly Ash

Green Approach for Rare Earth Element (REE) Recovery from Coal Fly Ash

Synthesis of a Coal Fly Ash‐Based NaP Zeolite Using the Microwave‐Ultrasonic Assisted Method: Preparation, Growth Mechanism, and Kinetics

Advances and Outlook of Heavy Metal Treatment Technology from Municipal Solid Waste Incineration Fly Ash: A Review

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