(345a) Rare Earth Elements Production from Geothermal Power Plant Using Magnetic Nanofluids

Extracting rare earth elements (REE) from geothermal brines is a very challenging problem due to the low concentrations of these elements and engineering challenges with traditional chemical separations methods involving packed sorbent beds or membranes that would impede large volumetric flow rates of geothermal fluids transitioning through the plant. We are demonstrating a simple and cost-effective magnetic nanofluid-based method for extracting rare earth metals from geothermal brines out from geothermal power plant. Core-shell magnetic nanoparticles are produced that contain a magnetic iron oxide core surrounded by a shell made of an Indium metal-organic framework (MOF) sorbent functionalized with chelating ligand diethylenetriamine (DETA) which is selective for the rare earth elements. The results of a study on the operating parameter matrix for the magnetic separator showed that it is possible to achieve a high (>99%) magnetic particle retention rate under appropriate combinations of magnetic power and liquid flow rate. It was found that the magnetic force may impact the integrity of the core-shell nanoparticle and lead to potential Fe leakage. The porous iron oxide core was replaced by a dense iron oxide core to greatly reduce the generation of Fe³⁺ in long term operation. The adsorbent life time was evaluated in both static and cycling manner by comparing the REE adsorption performance before and after extended hour (over 500h) experiment. In a case study, the internal return rate (IRR) of using the magnetic nanofluid extraction technology to separate Eu from Salton Sea geothermal brine was estimated to be over 18%, which indicates a promising economic feasibility.