Recovery of Rare Earth and other Strategic Materials from Coal Ash

EPA Grant Number: SU836143
Title: Recovery of Rare Earth and other Strategic Materials from Coal Ash
Investigators: Mohanty, Manoj K.
Institution: Southern Illinois University - Carbondale
EPA Project Officer: Sergeant, Anne
Phase: I
Project Period: September 1, 2015 through August 31, 2016
Project Amount: $14,750
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Research Category: P3 Awards , Pollution Prevention/Sustainable Development , Sustainability , P3 Challenge Area - Materials & Chemicals

Objective:

The main goal of this project to investigate different separation techniques for the extraction of REEs and other strategic minerals like Ge, Ga, etc. from CCBs. A leaching process followed by a suitable solvent extraction method will be investigated for the recovery of rare earth minerals (REM) from the coal ash leachate solution. The specific project objectives include the following:

  1. To characterize a variety of coal fly ash and bottom ash samples generated from the combustion of different types of coal.
  2. To investigate extraction of the REMs from coal fly ash and bottom ash using combined physical and chemical separation techniques.
  3. To envision a process flowsheet(s) for the REM recovery from coal ash, which could vary based on the characteristics of REMs present in coal fly ash and bottom ash generating from different types of coals founds in different regions of the US.A.

Approach:

Several coal ash samples will be collected from thermal power burning eastern U.S. coal, midwestern coal and western U.S. coal. Different characterization studies will be carried out on the fly ash and bottom ash samples to study the particle size, structure and mineralogical composition of each of these ash samples. The ash samples will high (>500 ppm) concentration of REE concentration will go through the physical and chemical separation steps to recover REO concentrates.

Physical and hydrometallurgical separation techniques will be investigated. Experiments such as float and sink will be carried out to find out the possibility of preconcentrating REEs minerals using density separation methods. Flotation will be examined to check the possible partitioning of REMs based on the differences in surface properties. Leaching tests will be carried out on the preconcentrated REE feedstock generated from the physical separation tests using both mild and strong lixiviants to examine both grade and recovery optimums achievable from the leaching process. Solvent extraction step will be utilized to purify the pregnant leachate solution by removing many of the undesired minerals using organic extractants. The REE minerals loaded on the extractants will be stripped off using hot water and the aqueous solution of REEs will be allowed to precipitate by mixing with oxalic acid. The REE oxalates will be calcined to produce REO powders.

Expected Results:

A successful completion of both phases (I and II) of this project will develop a suitable processing flowsheet(s) to extract REMs from fly ash and bottom ash generating from different regions in the US. Project results will be disseminated in the scientific and engineering communities through oral/poster presentations/publications at conferences/professional meetings.

Supplemental Keywords:

rare earth elements, REEs, characterization, hydrometallurgy, flotation, leaching, solvent extraction