A number of specialized metals (“critical materials”) are indispensable to modern communication, medical and clean energy technologies. Due to their technological importance and the relatively limited global options for sourcing them, advancing new recovery and recycling processes is an area of active research and development. However, new industrial processes often mean the generation of new wastes. For hydrometallurgical processes, wastewaters often contain residues of the target metals as well as processing agents. Wastewaters that impair treatment performance will not be accepted by municipal treatment plants. As part of our work for the Critical Materials Institute (CMI), an Energy Innovation Hub funded by the U.S. Department of Energy, we have been examining the potential for disruption of biological treatment by wastes from new recovery and recycling approaches developed by CMI partners. Bench-scale reactors seeded with activated or anaerobic sludge from a municipal treatment plant, agar plates inoculated with sludge microorganisms, and pure cultures of the ammonia oxidizing bacterium <i>Nitrosomonas europaea</i> have been challenged with various wastewaters or process components to evaluate activity and growth metrics and effects on microbial community composition relative to control cultures. In particular, we have examined potential impacts to biological wastewater cultures from new approaches/chemistries for rare earth element (REE) leaching from solid wastes and REE separation by solvent extraction. Results vary by test system but some general observations to date include: (1) effects from REE are usually not observed until total loadings are very high (e.g., ≥ 25 ppm nominal concentrations); (2) organic ligands used with REE may be more problematic than the residual metals; and (3) impacts can be manifested by changes in microbial community composition. Much remains to be understood regarding the mechanisms underlying these observations.

New critical material recovery and recycling processes lead to new wastewaters

ACS Fall 2020 Virtual Meeting

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