Conference Agenda

As Li-ion batteries are increasingly being deployed in electric vehicles and grid-level energy storage, the demand for Li is growing rapidly. Extracting lithium from unconventional aqueous sources such as geothermal brine, oil and gas produced water, salt lake water, and seawater will play an important role in meeting lithium demand. Electrochemical separation does not require a constant supply of chemical reagents and can be desirable lithium extraction technology. The objective of this work is to test the hypothesis that intercalative deionization can achieve lithium extraction from high-salinity brines with high selectivity. We designed an intercalative deionization cell with a lithium-intercalation electrode as the working electrode for the separation of lithium from brines. LiFePO4 (LFP) electrode was fabricated and pre-delithiated for lithium extraction. A continuous-flow cell was designed with brine-in-water-out configuration. We investigated the selectivity of lithium separation in electrolyte solutions with different cation concentration ratios as well as in simulated brines. We also systematically investigated the extraction performance as a function of operating parameters. Results show that LiCl with a purity of >95% can be extracted from high-salinity brine with an initial Li/Na molar ratio of 1/77 and in the presence of divalent cations. Our work demonstrates the potential to apply electrically-driven intercalative deionization in direct lithium extraction from high-salinity aqueous sources.

The global need for electronics has been continuously rising; consequently, electronic waste (e-waste) generation has also increased. For example, in 2019, the United States generated 3.1 million metric tons of e-waste. It was estimated that this amount of e-waste was worth about $53 billion when considered a secondary source of critical elements. Numerous chemical and metallurgy-based methods have been developed to recover these elements from e-waste; however, such methods have high environmental footprints. Recently, phytoextraction has received attention for metal recovery directly from e-waste, and the metal-accumulated biomass has been further used as a raw material for graphitic composite synthesis. Previously, we have used Eleocharis acicularis to extract critical metals such as indium from the e-waste. The plant biomass was then graphitized to synthesize metal-graphitic composites to promote the circularity of resources. However, the sustainability of phytoextraction from e-waste compared to conventional methods remains unclear. In this collaborative research, the environmental impacts and economic viability of phytoextraction and graphitization are evaluated and compared to existing technologies. This study leverages Python to simulate environmental impacts via life cycle assessment (LCA), costs via techno-economic analysis (TEA), and create a shared resource in open-source libraries. Aiming for a cradle-to-cradle assessment, the study uses liquid crystal display (LCD) screens as the waste input, Eleocharis acicularis as the phytoextraction agent, and a processing time of 18 days. The outcomes of our studies have the potential to encourage the scientific community to consider biology-based approaches such as phytoextraction for the recovery of critical elements from e-waste.

Membrane-capacitive deionization (M-CDI) is a promising electrochemical process capable of recovering lithium from brine wastes. Many studies have focused on the selectivity of lithium over divalent ions (e.g., Mg²⁺), while the essential challenge of M-CDI lies in the poor selectivity among monovalent ions (e.g., Na⁺) due to the same charge and similar hydrated radii.

This study address this prominent challenge by shifting the membrane modification vision from hydrated ion removal to dehydrated ion removal and integrating membrane with faradaic electrode. Specifically, zeolitic imidazolate framework-8 (ZIF-8)/polypyrrole/polystyrene sulfonate (PSS) modified cation exchange membrane (CEM) is incorporated with λ-Mn₂O₄ as the cathode to enhance the selectivity towards lithium. Angstrom-scale pore window (3.4 Å) and cavity window (11.6 Å) of the modified membrane provides biomimetic transport of Li⁺ over other monovalent ions due to smaller Li⁺ dehydrated radii. Meanwhile, conductive polypyrrole/PSS composition can compensate the poor conductivity of ZIF-8 and facilitate Li⁺ transport. In addition, the λ-Mn₂O₄ cathode possesses stable spinel structure and preserved nodes towards Li⁺, leading to an outstanding lithium adsorption capacity (23.7 mg/g) and high selectivity over Na⁺ and Mg²⁺ (3.5 for Li⁺/Na⁺ and 31 for Li⁺/Mg²⁺),surpassing all the reported values. Molecular dynamics (MD) is being used to decode the black box of ion transport and stagnation within the modified ZIF-8 membrane.

This study unveils an innovative membrane modification strategy for M-CDIs to advance the energy efficiency and the selectivity of lithium recovery, and establish a platform to develop biomimetic membranes for other environmental processes (e.g., electrodialysis and battery electrode deionization).

Selenium, a crucial trace element that is indispensable to the sustenance of all living beings, has gained significant attention as a water treatment challenge in multiple sectors, including mining, oil refining, and power generation. However, conventional methods of removing selenium are complex and expensive due to low discharge limits and large volumes of wastewater. In this study, we developed and tested a wood-based reactive evaporator, which reduces the volume of the wastewater and recovers selenium at the same time. The unique properties of the wood evaporators allow for a fast evaporation rate of 2.6 LMH and a selenium recovery efficiency of 96%. This is achieved by converting 95% of solar energy into thermal energy for water evaporation and concentrate selenium to the surface, while using the remaining 5% for photocatalytic reduction. Additionally, the acidic nature of the wood provides a preferred pH environment (i.e., pH < 6) for selenium reduction even with alkaline water sources, and the photocatalytic reaction can be sustained without additional hole scavengers. Furthermore, our evaporator has shown success in recovering other heavy metals and can be adjusted for selectivity.

Precise ion-ion separation using membranes has recently emerged to become one of the frontiers for membrane-based separation due to the increasing demand for selective separation in resource recovery and extraction from aqueous feed streams. An important application is the extraction of lithium from brine. The critical step of lithium extraction is to separate lithium (Li) from magnesium (Mg). Nanofiltration (NF) and electrodialysis (ED) have been applied for Li/Mg separation. NF membranes prefer the passage of Li+ while retaining Mg2+ via size-dependent exclusion and electrostatic exclusion. Monovalent selective cation exchange membranes (CEMs) used in ED can selectively transport Li+ mainly due to the positively charged surface coating layer. Coating a dense polyamide film on top of CEMs can also enhance Li/Mg selectivity. More recently, the state-of-the-art NF membranes, thin film composite polyamide (TFC-PA) membranes, have been tested to replace CEMs in ED for a better Li/Mg separation. This presentation aims to theoretically compare the Li/Mg separation performance of NF and ED with different composite membranes using a unified mass transport model, i.e., the solution-friction model. The comparison will discuss how membrane properties and operating conditions affect the Li/Mg separation from coupon-scale to module-scale in selectivity, lithium flux, lithium recovery, and energy consumption. The comparison will provide new insights to the design of composite membranes and process innovation for Li/Mg separation.