Fan Shi, PhD
Principal Materials Scientist
NETL

Multi-functional Sorbent Technology (MUST) for CO2 Capture and Critical Metals Recovery

Carbon sequestration entails a multi-step process in which anthropogenic CO2 emissions are captured from CO2-laden process gas streams and permanently stored. Carbon capture is a critical step in the process and accounts for a considerable portion of the overall cost. Across the literature, a multitude of functionalized silica sorbents demonstrate high-capacity CO2 capture and offer advantages over the benchmark liquid monoethanolamine (MEA) process, including reduced heat duty and improved CO2 mass transfer. However, low sorbent stability still remains an issue. Basic immobilized amine sorbents developed at NETL were successfully tested at bench and pilot-scales and demonstrated their promising potential for large scale CO2 removal from post-combustion sources and ambient air. This is owed to the sorbents’ optimized tradeoff between CO2 capture capacity and thermal stability observed over multiple and even 100 adsorption-desorption cycles. Within the last few years, key technological milestones diversifying the commercialization potential of the NETL’s sorbent were achieved. These include commercial (3 kg) pelletization of particles into rods and spheres for moving bed rectors; incorporation into a room temperature sorbent regenerated by microwave irradiation for a DAC process; and spinning into hollow chemisorption fiber sorbents (CHEFS) for rapid temperature swing adsorption systems.

Critical Metals (CMs), including Rare Earth Elements (REEs), aluminum, manganese, cobalt, and others outlined by the U.S. Department of the Interior’s Geological Survey are essential to the national and economic security of the US, and whose supply chain is susceptible to disruption. Because of the negative environmental impacts inherent with the conventional mining and processing of solid ores for CMs, adsorption-based recovery of naturally dissolved species from coal wastewaters is appealing. Acid mine drainage (AMD) remains a relatively untapped source that can be rich in REEs, and especially in Al, Mn, and other CMs. NETL’s Multi-functional Sorbent Technology (MUST) has been developed originally from the functionalized silica sorbents for carbon capture. Ongoing work aims to find AMD sites enriched with either REEs or other CM, and to perform additional field tests at these sites. Overall, our work shows the viability of recovering CMs from AMD and other coal waste streams, using a fixed-bed adsorption system that can also employ a selective elution technique to achieve highly purified metal resources.