(368ab) Development of Sustainable Processes Via Integrated CO2 Utilization and Structured Ligand Design for Critical Metal Recovery and Renewable Chemical Production

Transitioning to a net-zero carbon economy necessitates substantial investment in renewable energy infrastructures, heavily reliant on energy-relevant metals such as REEs, Cu, Ni, and Zn. Conventional mining methods, the primary source of these metals, present sustainability challenges, including reliance on ores of decreasing purity, extensive acid usage, waste generation, and substantial CO₂ emissions. These factors contribute to 7.9% of global CO₂ emissions. Addressing these challenges requires developing integrated carbon capture and utilization cycles to recover energy-relevant elements and promote a circular economy. My research aims to pioneer sustainable pathways and technologies for extracting and separating critical metals from unconventional resources, focusing on process development and manufacturing innovations. This involves two main themes: (1) utilizing greener solvents to enhance the hydrometallurgical extraction of energy-relevant elements from waste feedstocks and (2) designing selective ligands to tailor metal recovery through solvent extraction and adsorption processes.

Project 1: Sustainable Extraction of Critical Metals from End-of-Life Materials

The rapid expansion of the electronics industry poses challenges in handling end-of-life electronic products. Critical elements like Zn, Cu, Ni, and REEs are vital in electronics, magnets, and batteries, requiring sustainable sourcing. Despite recycling efforts, a significant portion of REEs ends up in landfills or waste-to-energy plants. This project focuses on identifying, characterizing, and understanding sustainable extractants for dissolving critical elements from end-of-life feedstocks such as WTE FA and WEEEs. The objective is to establish green chemical input streams to enable the selective extraction and recovery of REEs. We perform comprehensive analyses using solid-state characterization techniques (XRD, BET, TGA) and model solubility limits with tools like Visual MINTEQ. Dissolution and carbonation kinetics are investigated through ICP-OES.

Project 2: Developing Structured and Stimuli-Responsive Ligand Scaffolds for Highly Selective Separation and Recovery of REEs

Recovering and purifying critical elements from unconventional sources is challenging due to the presence of complex mixtures of background metal ions. This project employs molecular design principles to investigate stimuli-responsive ligands for selectively extracting REEs from unconventional resources. These ligands are customized for specific charge and ionic radii characteristics to capture REEs effectively. Designed to exhibit pH responsiveness or undergo CO₂-induced pH shifts, the ligands release captured REEs efficiently. We develop one-pot synthesis methods for producing large-scale quantities of Schiff-based ligands and characterize them using NMR and FTIR. Additionally, cerium carbonates and cerium oxides are characterized via XPS to probe oxidation states, providing insights into their behavior in the reactive separation process.

Project 3: Tuning Selective Recovery of Energy-Relevant Metals Using Rational Design of Aldoxime-Based Ligands

Energy-relevant metals are crucial for renewable energy infrastructures. Unsustainable mining practices necessitate greener extraction technologies. This project investigates the selective recovery of elements using aldoxime-based ligands, focusing on Ni in the presence of atomically similar elements like Co, Mn, Zn, and Cu. We delve into the complexation mechanisms for these metals and optimize operating conditions for their extraction in a solvent extraction system. DFT calculations probe processes such as dimerization, deprotonation, and complexation of metal complexes were verified experimentally. Complexes formed during solvent extraction are characterized using UV-Vis, NMR, and ICP-OES to gain insights into their structural properties and behavior.

Project 4: Sustainable On-Demand Photochemical Production of H₂O₂ with Anthraquinone-Based Hybrid Materials

H₂O₂ is vital in wastewater treatment, bleaching, and eco-friendly disinfection applications. Traditional large-scale production methods using the anthraquinone oxidation (AO) method are inefficient due to environmental challenges and separation issues. Our technology introduces a novel approach by incorporating anthraquinone molecules into hybrid materials, facilitating efficient photosensitization using visible or near-visible light within a single aqueous phase. This innovation improves environmental sustainability and process efficiency. We investigate the photochemical processes underlying peroxide production and optimize batch and continuous flow setups to achieve commercially significant concentrations of H₂O₂. The project involves synthesizing and characterizing functionalized anthraquinones using ss-NMR, TGA, FTIR, and Raman spectroscopy. Quantification of H₂O₂ production and byproducts is performed using UV-Vis and HPLC.

Research Advisors: Ah-Hyung Alissa Park, Aaron J. Moment