B. Lusk, B. Rittmann, C. Ray, C. Zhou, L. Thompson
Keywords: critical minerals, biorecovery, bioremediation, biocatalyst, environmental biotechnology, gold
Summary:Conventional physical and chemical processes for recovery of platinum group metals (PGM) and Rare Earth Elements (REE) are costly, ineffective, or introduce contamination into the environment. Alternatively, microorganisms can biologically recover soluble PGM and REE as metallic nanoparticles: e.g. convert Rh(III) to Rh(0) (metallic rhodium) or convert Nd(III) to Nd2S3 (solid nanoparticle) using H2 gas as an electron donor. Microbial reduction of Rh(III) or conversion of Nd(III) via reduction of sulfate and ultimate precipitation with S2- is advantageous because it yields controllable nanoparticles having large specific surface area and high catalytic activity. The Membrane Biofilm Reactor (MBfR) enables in situ microbial recovery of 99% of PGM, REE, and other valuable metals including gold, silver, and nickel as nanoparticles. The MBfR has a compact size due to its high membrane surface area. Its modular design enables it to be customized to meet customer needs. For example, the modules can be run in parallel to accommodate large flows or operated in series to recover multiple materials from the same water source. Furthermore, the modularity simplifies repair and maintenance since redundancy in the system provided by parallel modules enables the treatment process to continue with minimal perturbation. The modular design, in concert with bubble-free H2 delivery, gives the MBfR unparalleled specificity and a minimal footprint. The MBfR also is the only reductive biotechnology capable of capturing Rh, Ru, and Ir, materials that are practically unrecoverable using competing ionic exchange membranes. The customers for this innovation are industries that generate wastewater containing PGM, REE, or the aforementioned valuable materials. Precient’s beachhead market is the valuable-metals recycling and refining industry and currently has two operational lab-pilots from customers in this industry. Wastewater from the valuable-metals recycling and refining industry contains valuable materials at concentrations >500 ppm. Globally, this industry annually loses ~$10 billion in precious metals and REE in their effluent water. Conservative estimates predict an annual 20x return on investment for an MBfR based on the value of recovered nanoparticles from wastewater. The MBfR is essential because recycling provides 25% of the global demand for valuable metals. Increasing demand has created a 4-5% annual growth rate for precious metals and REE recycling. For example, demand for these materials is increasing in the semiconductor industry due to automation, the global shift toward telecommuting and the associated increase in internet traffic, increased demand for handheld devices, and in the automobile industry due to electrification and heightened demand for efficient catalytic converters. Furthermore, the solar industry, which has averaged a 49% growth rate over the past 10 years, accounts for 10% of world demand for silver. To continue at current growth rates, these industries will place a heightened demand upon recycled materials. Due to the scarcity and critical role of these valuable metals in constructing cutting-edge technologies, many of these metals are at record high prices. Several countries, including the USA and many in the EU, have declared these valuable metals as ‘materials in critical supply’ and essential for the sovereignty and defense of the nation.