PNNL

Abstract

Rare earth elements (REE) are critical materials having a wide variety of applications such as generating and storing renewable energy. Extracting rare earth metals 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 geothermal power plant. We are demonstrating a simple and highly cost-effective nanofluid-based method for extracting rare earth metals from geothermal brines. Core-shell composite nanoparticles that contain a magnetic iron oxide core surrounded by a shell made of metal-organic framework (MOF) sorbent functionalized with chelating ligands are produced to selectively extract rare earth elements. Baseline values of the important parameters including rare earth metal concentration and price, adsorbent need, cost and lifetime have been identified. This information together with a flowsheet model were used to estimate the operating and capital costs of the extraction process. A techno-economic performance analysis of extraction systems using a modified In-MOF as the adsorbent showed potential to generate a promising internal rate of return (IRR) higher than 16%. Sensitivity analysis has been done on some key parameters such as REE concentration and price and adsorbent cost to reveal their impacts on IRR.