(316a) Selective Separation of Rare Earth Elements from Industrial Waste Streams Using Gold Nanoparticles Functionalized with Peptides Derived from the EF-Hand Loop 1 of Lanmodulin

Over the last few decades, the demand for rare earth elements (REEs) has significantly increased because of their use in a wide range of applications and technologies such as electric cars, cell phones, computers, wind turbines, satellites, and biomedical devices, etc. However, global reserves of REEs are limited and as of now, the recovery and recycling from the end-of-life products and industrial waste streams is minimal. Due to the extremely similar atomic radius and charge of the ions, it has become a challenging task to identify a cost-efficient and eco-friendly separation method that could allow a sustainable supply of REEs. Among many proposed schemes, biosorption using proteins and peptides is a promising approach for recovering REEs due to several advantages including low cost, high selectivity, high regeneration, and fast kinetics. Peptides have additional advantages over proteins; short chains of amino acids make them easier to tune, the synthesis of peptides is relatively easy, the peptides are robust, and the cost of production can be low.

In the present work, several peptides are designed based on EF-hand loops of the lanmodulin protein and are investigated for the selective separation of REEs when functionalized on a gold substrate. A simulated solution comprised of Ce (III), Nd (III), La (III), and Y (III) mimicking the concentrations of REEs in phosphonium waste is generated in the lab. The peptides are functionalized on gold nanoparticles (GNPs) and adsorption studies are performed. The concentrations of the ions in solution are estimated using inductively coupled plasma optical emission spectroscopy (ICP-OES) and the selectivity of the peptides for one REE over others is estimated. Selectivity is compared with the ideal selectivity, defined as the ratio of the association constants (ideal selectivity α_i/j = K_a,i /K_a,j where K_a,i and K_a,j are the association constants of species i and j obtained from isothermal titration calorimetry (ITC) experiments) in solution. The binding affinity of the surface-bound peptides with REEs is studied using quartz crystal microbalance with dissipation monitoring (QCM-D) and the Langmuir adsorption model. The overall goal of this work is to identify the peptides that are selective for the specific REEs with potential application in industrial separation processes.