S. Ashkar and M. Rogers
RTX BBN Technologies,
United States
Keywords: Neodymium, microbes, electronic waste
Summary:
Typically only around 16% of REEs are recycled from end-products, with the rest discarded as waste and removed from the materials cycle. Despite their capability for reuse, the recycling of elements currently creates a negative environmental burden and is not cost effective. Recycling e-waste would provide a valuable, steady, domestic source of rare earth metals to manufacturers while also reducing waste. Currently, the main hurdle to recycling rare earth elements is the cost required to purify the mixtures obtained from consumer devices and the harsh chemicals used in current recycling techniques. We have isolated a novel microbial consortium that is able to degrade waste Neodymium-Iron-Boron magnets (NdFeB) into their component elements. This process can be performed at room temperature with stirring and does not require any strong solvents or other harmful inputs. A robust culture of our consortium is grown with the target substrate. The culture is then grown on a minimal media containing a high percentage of acetate – we hypothesize that acetic acid plays a major role in the initial extraction of the metals from the magnet. During normal growth of the consortium, the pH of the system drops to approximately 3.5, then rapidly climbs to a pH of approximately 12. Oxygen availability in the reaction drops, while hydrogen production increase significantly. When magnets are ground to a size of 100um to 1mm in size, the extraction process takes approximately 29 hours. Whole magnets, with a correspondingly lower exposed surface area, takes weeks. From a 1 kilogram feedstock of ground magnets, we can recover approximately 200 grams of precipitate containing rare earth metals, as well as organic volatiles that are removed by baking at 400C. We have tested loading percentages from 10% to 100% weight to volume. This process allows us to recover a precipitated fragment that is rich in rare earth elements, including 48% neodymium, 4.7% dysprosium, and 7.5% praseodymium. We are currently scaling the recycling process from bench scale to an automated 250 liter reaction with real-time measurement capabilities. Currently, we are able to process one kg per liter per day in batch culture. The 250 l reactor will be used to characterize the reaction at scale, and to further determine optimal conditions for the recycling reaction. Additionally, we will characterize different input materials to determine optimal ingredient for our reaction. The reaction will then be automated to achieve maximum rates/yields. In addition, we can manipulate the conditions of the reaction to yield novel outputs, such as specific mixtures of oxides or other salts. The reactors are designed for parallelization to allow further scale up, with an ultimate goal of developing a 1000 l pilot plant.The reactors are designed for parallelization to allow further scale up, with an ultimate goal of developing a 1000 l pilot plant. Our cost effective, environmentally friendly biologic method of recycling e-waste will provide a stable stream of these essential elements to domestic manufacturers.