Abstract
Rare earth elements (REEs) are essential for many clean energy technologies. Yet, they are a limited resource currently obtained through carbon-intensive mining. Here, bio-scaffolded proteins serve as simple, effective materials for the recovery of REEs. Surface expression of the protein lanmodulin (LanM) on E. coli, followed by freeze-drying of the microbes, yields a displayed protein material for REE recovery. Four REE cations (Y(3+), La(3+), Gd(3+), and Tb(3+)) are captured efficiently, with over 80% recovery even in the presence of competitive ions at one-hundred-fold excess. Moreover, these materials are readily integrated into a filter with high capture capacity (12 mg g(-1) dry cell weight) for the selective isolation and recovery of REEs from complex matrices. Further, the proteins in the filter remain stable over ten bind-and-release cycles and a week of storage. To improve the deployability of this filter material, a simple colorimetric assay with the dye alizarin-3-methyliminodiacetic acid is incorporated. The assay can be performed in under 5 min, enabling rapid monitoring of REE recovery and filter efficiency. Overall, this low-cost, robust material will enable environmentally friendly recycling and recovery of critical elements.