Microwave-Assisted Comminution for Coal Ash REE Extraction
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Solution Overview
Problem
Current methods for extracting rare earth elements (REEs) from coal ash are inefficient, requiring aggressive acid solutions and high energy inputs, leading to low recovery rates and environmental hazards, while existing pre-treatment processes do not effectively address the challenge of entrapped REEs in aluminosilicate glass phases.
Innovation Solution
A microwave-assisted comminution method is employed to create defects in coal fly ash particles, enhancing the diffusion of acid solutions and improving the hydrometallurgical recovery of REEs, which involves mixing coal ash with a carbon source, heating in a microwave cavity, and subsequent acid leaching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If aggressive acid solutions (HNO3 >3-6 M) are used for leaching REEs from coal ash, then REE recovery increases, but acid cost and environmental hazards increase
Solution Approach 1:
The patent applies preliminary mechanical activation (ball milling) and chemical pre-treatment (oxidation with H2O2 or NaClO) to coal ash particles before leaching. This pre-treatment creates defects and increases surface area in the aluminosilicate glass phase, making REEs more accessible. As a result, milder acid solutions (0.5-2 M HNO3) can achieve the same recovery rates (40-60%) that previously required aggressive concentrations (>3-6 M), thereby reducing acid cost and environmental hazards while maintaining productivity
2Productivity
If traditional acid leaching is used without pre-treatment, then process simplicity is maintained, but REE recovery remains low (<40-50%)
Solution Approach 1:
The patent introduces a pre-treatment stage involving mechanical activation (ball milling for 1-24 hours) and chemical oxidation (H2O2 or NaClO treatment) before the main acid leaching process. This preliminary action modifies the coal ash particle structure, creating defects and increasing surface area, which significantly improves REE accessibility. The additional steps increase process complexity but enable recovery rates of 40-60% compared to <40-50% without pre-treatment, justifying the complexity through substantial productivity improvement
3Productivity
If high concentrations of acid are used, then leaching efficiency improves, but equipment corrosion and operational cost increase
Solution Approach 1:
The patent employs mechanical activation (ball milling) and chemical oxidation (H2O2 or NaClO) as pre-treatment steps that modify the coal ash particle structure before leaching. This creates defects and increases surface area in the aluminosilicate glass phase, making REEs more accessible to leaching agents. Consequently, milder acid concentrations (0.5-2 M HNO3) can achieve comparable leaching efficiency to aggressive acids (>3-6 M), reducing equipment corrosion and operational costs while maintaining productivity
4Productivity
If conventional roasting methods are used to beneficiate coal ash, then REE concentration improves, but energy consumption and process complexity increase
Solution Approach 1:
The patent replaces conventional thermal roasting methods with mechanical activation (ball milling) and chemical oxidation (H2O2 or NaClO treatment) to achieve beneficiation of coal ash. This mechanical-chemical approach creates defects and increases surface area in the aluminosilicate glass phase, improving REE concentration and accessibility without the high energy inputs required by thermal methods. The substitution significantly reduces energy consumption while achieving comparable or superior REE concentration through mechanical and chemical rather than thermal means
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases the efficiency of REE extraction, reduces the need for high acid concentrations, and lowers energy consumption, making the process more environmentally friendly and cost-effective compared to traditional methods.
Implementation Method 1
microwave processing the first mixture to generate processed coal fly ash particles
Implementation Method 2
enhancing the diffusion of acid solutions and improving the hydrometallurgical recovery of REEs
Data Source
AI summary
In one aspect, the disclosure relates to a microwave-assisted comminution method for achieving more efficient beneficiation and later hydrometallurgical recovery of rare earth elements and other metals from coal fly ash particles. The method requires only a short processing time, is energy efficient, allows for better process control, and is environmentally advantageous compared to current methods. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present disclosure.