(586a) Superstructure Optimization Enabled Design Heuristics and Material Property Targets for Continuous Diafiltration Membrane Cascades

In a recent consensus report, the US National Academies highlight opportunities to transform Separations Science to better address global environmental challenges with sustainable technologies.[1] For example, several forecasts predict that vehicle electrification will lead to a massive demand for lithium which will exceed its current production capacity within a decade [2]. , While recycling lithium ion batteries (LIBs) has many environmental benefits including reduced environmental impact from conventional lithium mining techniques and diverting waste and pollution caused by disposing valuable elemental resources (Li, Co, Ni, etc.), it remains uneconomical compared to Li harvesting from primary sources (e.g., mining). [3-5] This example highlights how multidisciplinary innovations across scales are often required to solve global engineering challenges. For LIB recycling, process systems engineering can help accelerate technology development by i) systematically optimizing process flowsheets tailored to site specific criteria and ii) setting quantitative materials, device, and unit operation performance targets to guide research at smaller length scales. Inspired by the above mentioned National Academies report, we recently proposed a molecules-to-systems engineering design framework that integrates data-science, domain expertise, and experimental measurements to accelerate innovations in separations and beyond. [6] This talk highlights opportunities for superstructure optimization to enable molecular-to-systems engineering of novel membrane separations.

In diafiltration systems, dialysate is strategically fed to the retentate side of a membrane to mitigate concentration polarization which enables more efficient batch or continuous staged membrane cascades. Although diafiltration membrane systems have been studied for over 20 years, their industrial use is limited to high-value niche separations including buffer exchange and protein purification. One possible reason for less widespread use of diaflitration is the lack of systems engineering research related to diafiltration system design, operation, and control.

In this talk, we present a novel superstructure optimization framework to design diafiltration membrane cascades [7]; we show optimally designed diafiltration systems are efficient Li/Co fractionation steps for LIB recycling processes and quantify the process-scale benefits of next-generation membrane materials. Specifically, our framework encodes all realistic diafiltration cascade configurations into a superstructure; through continuous optimization, we systematically search over these configurations (with complex recycle and feed injection strategies) while considering membrane areas, flowrates, and concentrations of all streams as decision variables. The optimal system designs show how dialysate buffer is used to offset concentration effects in membrane filtration to recover highly concentrated metal rich solutions. Using an epsilon-constrained multiobjective optimization, we identify Pareto-optimal configurations that balance permeate (Li) and retentate (Co) product recoveries and explore tradeoffs in staging complexity versus membrane area. We then distill thousands of optimal diafiltration configurations into six design heuristics. We justify each design heuristic using governing transport and thermodynamic phenomena and draw analogies to design short-cut methods for other staged separations (e.g., absorption, distillation). Finally, we highlight how our framework enables top-down design by studying the effects of alternate membrane characteristics on the performance of the cascade. To our knowledge, this is the first optimization-based analysis of diafiltration cascade systems. We conclude by sharing opportunities for process systems engineering to advance diafiltration technologies and more broadly membrane science.

References:

[1] National Academies of Sciences, Engineering, and Medicine. A Research Agenda for Transforming Separation Science. (2019).

[2] Sonoc, A., & Jeswiet, J. (2014). A Review of Lithium Supply and Demand and a Preliminary Investigation of a Room Temperature Method to Recycle Lithium Ion Batteries to Recover Lithium and Other Materials. Procedia CIRP, 15(C), 289–293. https://doi.org/10.1016/j.procir.2014.06.006

[3] Li, L., Deshmane, V.G., Paranthaman, M.P., Bhave, R.R., Moyer, B. A., Harrison, S., (2018). Lithium Recovery from Aqueous Resources and Batteries: A Brief Review. Johnson Matthey Technology Review, 62(2), 161–176. https://doi.org/10.1595/205651317X696676

[4] Swain, B. (2017). Recovery and recycling of lithium: A review. Separation and Purification Technology, 172, 388–403. https://doi.org/10.1016/j.seppur.2016.08.031

[5] Flexer, V., Baspineiro, C. F., & Galli, C. I. (2018). Lithium recovery from brines: A vital raw material for green energies with a potential environmental impact in its mining and processing. The Science of the Total Environment, 639, 1188–1204. https://doi.org/10.1016/j.scitotenv.2018.05.223

[6] Eugene, E., Phillip, W., Dowling, A. (2019). Data Science-Enabled Molecular-to-Systems Engineering for Sustainable Water Treatment, Current Opinion in Chemical Engineering, 26, 122–130.

[7] Eugene, E., Phillip, W., Dowling, A. (2019). Material Property Goals to Enable Continuous Diafiltration Membrane Cascades for Lithium-Ion Battery Recycling, Proceedings of the 9th International Conference on Computer Aided Process Design (FOCAPD), 469-474.