Multifunctional membrane distillation for hypersaline brine treatment, low-grade heat harvesting and lithium recovery
Year: 2021
Type: dissertation
Abstract: Membrane distillation (MD), a thermally driven technology capable of desalinating hypersaline brine, has become increasingly attractive. However, the widespread industrial application of MD has been hindered by its low energy utilization efficiency. Adding new functions to MD by integrating other emerging processes can improve MD's energy utilization efficiency. This thesis investigated two derivations of MD: pressure-retarded membrane distillation (PRMD) and thermo-osmosis coupled thermally regenerative electrochemical cycle (TO-TREC). \nPRMD has the potential to recover the low-grade heat in terms of electricity by applying hydraulic pressure at the cold permeate side. Here, the feasibility of using PRMD for both desalination of hypersaline water and harvesting of low-grade heat was evaluated experimentally for the first time. Highly concentrated NaCl solution (4 M) can be desalinated with the salt rejection >99.9%, and electricity is generated in PRMD at the same time. However, the results also showed that the experimental PRMD performance was significantly affected by the pressure-induced membrane deformation. Thus, improving the mechanical stability of membranes would be the first critical step to improve PRMD performance. Further, controlling internal scaling and fouling is also critical for PRMD. \nTO-TREC is a new process in which the electrochemical process is integrated with the MD process for efficient lithium recovery. TO-TREC system extracted Li+ selectively from hypersaline brine and then released it into a recovery solution as LiCl with a high production rate. TREC harvests thermal energy from low-grade heat, saving >20% of electrical energy compared to conventional electrochemical methods. Li source solutions can be continuously concentrated by the coupled MD process, making it possible to utilize sources with low lithium concentration. The new process has an excellent potential to meet the growing global Li demands for various energy applications
Author: Ziwen Yuan
Language: English
Subfield: Water Science and Technology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3153306839