Year Established: 2015 Start Date: 2015-04-01 End Date: 2016-02-29
Total Federal Funds: $3,000 Total Non-Federal Funds: $7,436
Principal Investigators: Johan Schijf, Edward Landa
Abstract: The rare earth elements (REEs) are strategically important metals with a multitude of applications in high-tech industries, both civilian and military. China currently supplies about 97% of the world demand and this has raised awareness of the need to (re)develop potentially economic domestic REE deposits. The mining and processing of such ores generates effluents containing REEs and other co-occurring metals. Duckweed (family Lemnaceae) is a small floating aquatic plant that grows in still and slow-moving bodies of fresh water and wetlands worldwide. Due to its rapid increase in biomass, there is a high level of interest worldwide on the utility of duckweed as a phytoremediation agent for removal of soluble nutrients and hazardous substances from industrial and agricultural effluents. Prior studies by Weltje et al. (2002) examining the accumulation and elimination of the rare earth element lanthanum by duckweed (Lemna minor L.) noted a high bioconcentration factor (~17,000 to 33,000 L/kg), suggesting that duckweed may have utility as a biological removal agent in constructed wetlands and effluent retention ponds associated with the processing of REE-rich raw materials. The duckweed could be continuously harvested from ‘polishing ponds’ (i.e., the last steps in wastewater treatment) by skimming or related methods, and then ashed to recovery REE. Our proposed work would examine the potential use of duckweed (Lemna minor) in the bioremediation of rare earth element-containing effluents. Duckweed will be grown in a controlled environment-culturing facility. Exposures of duckweed to REEs will be done in replicated batches in growth medium, with sampling at different time points. Experimental variables will include pH, REE concentration, Ca concentration, and biomass-to-solution ratio. Additionally, no-plant controls will be periodically sampled to assess possible REE sorption on the culture vessel walls. REE uptake will be monitored by analyzing contents of the exposed duckweed tissue, using an inductively coupled plasma mass spectrometer (ICP-MS). Freeze-dried tissue from the main duckweed culture will also be used to assess sorbent properties of the non-living biomass.