We propose to develop and test a scalable method for efficient extraction of rare earth elementsand yttrium (REY) from acidic mine drainage (AMD)

The University of Pittsburgh will receive $199,999 from the Department of the Interior Office of Surface Mining Reclamation and Enforcement under the Science and Technology Projects Related to Coal Mining and Reclamation program (CFDA 15.255) from January 1, 2023 to December 31, 2024. The Cooperative Agreement will support development of a scalable method for efficient extraction of rare earth elements and yttrium from acidic mine drainage through collaborative research involving geochemical analysis, laboratory experiments, and geochemical modeling. Specific objectives include developing and validating an equilibrium modeling framework to describe co-precipitation and adsorption processes; conducting bench-scale experiments on simulated mine drainage to test model predictions and determine optimal treatment conditions; and designing a prototype modular, retrievable system for rare earth element capture and concentration that can be field tested. Results will be integrated into the PHREEQn AMDTreat water quality modeling tool and disseminated to stakeholders.

Specific objectives are to (1) develop amodeling framework that can accurately describe the CO precipitation and adsorption of reywith solid phases (mineral and amorphous) that are formed when coal AMD of variablecomposition is neutralized (2) validate specific model predictions using benchtop batch andcolumn flowthrough precipitation adsorption experiments on simulated AMD (3) develop andtest a prototype for manipulating high REY AMD in order to capture REY at or near thedischarge source at economic concentrations and (4) disseminate these findings to amdstakeholders and the greater scientific community, in part via integration into an innovativegeochemical modeling tool (phreeq n amdtreat), which will provide immediate on the groundresources for end users by providing cost benefit analysis and treatment strategies forrey recovery. This project is a collaborative effort involving expertise in coal mine drainage, laboratoryexperiments, geochemical analysis, and geochemical modeling from university of pittsburgh, USGS, and hedin environmental investigators. By building on our previous research, we willcombine geochemical equilibrium modeling with bench top experiments to determine precisetreatment conditions (e.g., PH, redox, metals and ligand concentrations) under whichprecipitation of solids can be achieved while concentrating REY removal at specific steps. Aphreeqc equilibrium model will be applied to identify potential interactions during theprecipitation of solids, including those containing REY, the distribution of aqueous and surface(sorption) species of REY and associated ions, and the sorbent composition and mass. Batchtitration and upflow column experiments will be used to evaluate potential for reycoprecipitation with AL and FE and to determine REY adsorption parameters on precipitatedamd minerals. Model calibration based on the experimental results will be used to determineoptimum conditions for the efficient precipitation of target and non target solids. Initialexperiments and modeling will involve simulated AMD and will be validated using amdcollected from a range of remediation sites. This combined and, most importantly, iterativeexperimental and modeling approach will be used to evaluate a wide range of variables in orderto design an up scalable modular, retrievable REY capture device that can be implemented infield testing of REY capture and recovery. The modeling, experiments, and technology demonstration will improve engineering designs thattarget REY recovery and provide additional economic incentive for AMD treatment of impactedstreams. Integration of results into the amdtreat water quality modeling tool (phreeq namdtreat)will provide end users the ability to up scale results to field application and aid incost estimates on the scale of individual AMD discharges. In addition, results will bedisseminated via scientific publications and meeting presentations. This project also involves thetraining of a graduate student in geochemical modeling, bench top experimental techniques, andamd remediation.