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Alumina Extraction from Coal Fly Ash via Pre-Desilication, Vacuum Reduction, and the Alkali Dissolving Method
Teng Li1, Yao Chen1, Xing Chen1
1College of Materials Science and Engineering, Chongqing University, Chongqing 400045, China.
Materials (Basel, Switzerland)
|July 15, 2026
Summary
This study introduces a novel process for coal fly ash (CFA) utilization, significantly reducing silica content. The method enhances alumina extraction efficiency, cutting material and energy use for cost-effective, eco-friendly applications.
Area of Science:
- Materials Science
- Chemical Engineering
- Environmental Science
Background:
- High silica content in coal fly ash (CFA) complicates alumina extraction, leading to increased material and energy demands.
- Efficient alumina extraction from CFA is crucial for its high-value utilization and reducing waste.
Purpose of the Study:
- To develop a novel, cost-effective, and energy-efficient process for alumina extraction from CFA.
- To improve the Al2O3/SiO2 ratio in CFA through pre-desilication.
- To enhance the overall efficiency of alumina recovery from CFA.
Main Methods:
- A three-stage process involving pre-desilication with NaOH, vacuum carbothermal reduction with Fe2O3 and CaO, and alkali dissolving.
- Pre-desilication removes amorphous silica, increasing the Al2O3/SiO2 mass ratio from 0.78 to 1.27.
- Vacuum reduction produces Fe-Si alloys and CaO·xAl2O3, followed by alkali dissolving for alumina extraction and magnetic separation for alloy recovery.
Main Results:
- Achieved an alumina dissolving rate of over 90% after alkali treatment.
- Reduced material input by 30.25% and energy consumption by 35.18% compared to processes without pre-desilication.
- Successfully recovered Fe-Si alloys via magnetic separation from the dissolved residue.
Conclusions:
- The proposed novel process offers a low-cost, energy-efficient, and environmentally friendly route for the high-value utilization of CFA.
- Pre-desilication is key to improving alumina extraction efficiency and reducing resource consumption.
- This integrated approach demonstrates a sustainable method for managing and valorizing coal fly ash.
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