Rare earth elements (REEs) are a set of 17 elements (lanthanides plus scandium and yttrium) that are not found concentrated in large ore deposits in nature. There has been huge growth in the amount of technology that uses REEs due to their diverse properties, but REEs are difficult to mine and expensive to separate. The global supply of REEs is largely controlled by a single country (China; &gt;95%), and the lack of a domestic supply has been identified as a vulnerability to U.S. economic security. To alleviate this vulnerability, economical extraction methods from traditionally overlooked domestic feedstocks such as coal fly ash (the ash left after coal is burned for power generation) are being explored. A traditional use of fly ash is as an additive to concrete aggregate, however, it is unknown whether acidified fly ash, after recovery of REEs, may be suitable for use in concrete. This study focuses on characterizing acidified fly ash after various amounts of REE extraction, with the goal of determining how much REE may be extracted without eliminating the functionality of the fly ash in concrete. We will characterize particle size and roughness of acidified fly ash particles using SEM imaging before and after exposing the ash to a range of pH extractions (0-8 M nitric acid). Raw and hydrothermally modified coal fly ash will be included. Using image analysis we will quantify changes in fly ash particle surfaces from the acid leaching steps. A future study will include mechanical testing of concrete cores made using the same acidified fly ash.

Coal fly ash geochemistry after acidic rare earth element recovery

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.