Ionic Liquid-Based Extraction and Separation for Recovery of Rare-Earth Elements from Coal Fly Ash.pdf

Ting Liu, Georgia Institute of Technology
Ching-Hua Huang, Georgia Institute of Technology

Description

Ionic liquid-based extraction and separation for recovery of rare-earth elements from coal fly ash Authors Ms. Ting Liu - United States - Georgia Institute of Technolog Prof. Ching-Hua Huang - United States - Georgia Institute of Technology Abstract Rare-earth elements (REEs) play a critical role in modern technologies. The United States currently lacks domestic REE supply but has a substantial reserve of coal fly ash (CFA) from annual production and decades of accumulation. CFAs are valuable sources for REE recovery, encompassing a comprehensive REE range with some at higher concentrations than rare earth mines. Recent studies from our research group have demonstrated that REEs can be preferentially extracted from CFA solids using a recyclable ionic liquid (IL), betainium bis-(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]). When CFA is heated with the mixture of IL and NaNO3 solution above 65 °C, most REEs will separate from the bulk elements and partition to the IL phase. Acid stripping of the IL removes REEs and regenerates the IL for reuse in additional extraction cycles. The IL-based REE-CFA recovery method has been applied to ten different types of CFA samples derived from different coal sources and ash recovered from disposal ponds. Results based on the evaluation of 34 elements confirmed the process’ high selectivity of REEs over other bulk and trace elements. Sc, Y, Nd, Sm, Gd, Dy, and Yb consistently exhibited high leaching and partitioning into the IL phase during extraction. Iron co-extraction was successfully limited by chloride complexation and ascorbic acid reduction. Aluminum showed a slight preference for the IL phase among all the ash samples. A subsequent precipitation process that adjusts the pH of the acidic solution using NaOH solution can partially remove Al with a minor loss of REEs. Overall, our recovery method combines REE extraction and separation into one step and can maintain a high REE recovery efficiency across various types of CFAs.

 
May 16th, 9:00 AM May 16th, 9:30 AM

Ionic Liquid-Based Extraction and Separation for Recovery of Rare-Earth Elements from Coal Fly Ash.pdf

Grand Rapids, Michigan

Ionic liquid-based extraction and separation for recovery of rare-earth elements from coal fly ash Authors Ms. Ting Liu - United States - Georgia Institute of Technolog Prof. Ching-Hua Huang - United States - Georgia Institute of Technology Abstract Rare-earth elements (REEs) play a critical role in modern technologies. The United States currently lacks domestic REE supply but has a substantial reserve of coal fly ash (CFA) from annual production and decades of accumulation. CFAs are valuable sources for REE recovery, encompassing a comprehensive REE range with some at higher concentrations than rare earth mines. Recent studies from our research group have demonstrated that REEs can be preferentially extracted from CFA solids using a recyclable ionic liquid (IL), betainium bis-(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]). When CFA is heated with the mixture of IL and NaNO3 solution above 65 °C, most REEs will separate from the bulk elements and partition to the IL phase. Acid stripping of the IL removes REEs and regenerates the IL for reuse in additional extraction cycles. The IL-based REE-CFA recovery method has been applied to ten different types of CFA samples derived from different coal sources and ash recovered from disposal ponds. Results based on the evaluation of 34 elements confirmed the process’ high selectivity of REEs over other bulk and trace elements. Sc, Y, Nd, Sm, Gd, Dy, and Yb consistently exhibited high leaching and partitioning into the IL phase during extraction. Iron co-extraction was successfully limited by chloride complexation and ascorbic acid reduction. Aluminum showed a slight preference for the IL phase among all the ash samples. A subsequent precipitation process that adjusts the pH of the acidic solution using NaOH solution can partially remove Al with a minor loss of REEs. Overall, our recovery method combines REE extraction and separation into one step and can maintain a high REE recovery efficiency across various types of CFAs.