Stable low-cost composite sulfonated PEEK polyethylene extraction membranes for battery purity Li2CO3 from brine

Abstract

To produce battery grade Li₂CO₃ from salt-lake brines has been a challenging task because of various contamination cations. Liquid-liquid extraction has been very selective in extraction of Li⁺ from brine, but loss of organic extractant has been critical issue from environmental, ecological concerns. This paper showed for the first time preparation of pure Li₂CO₃ based on a membrane extract-scrubbing-stripping-precipitate process via developing a low cost, chemically stable, high Li⁺ flux extraction membrane. Sulfonated poly (ether ether ketone)- polyethylene (SPEEK-PE) composite membranes were successfully developed by infiltrating SPEEK/methanol solution into an ultrathin porous PE separator. The hydrophilic nature of the dense SPEEK hydrogel layer prevented penetrating of the organic extractant into the membrane pores, improved the chemical stability of the membrane and maintained high ion transport flux. Higher sulfonation in SPEEK displayed better mass transfer coefficient K_e and only a 3 % decrease in K_e after ten days immersion in organics. To demonstrate the application of membrane extraction, battery-grade Li₂CO₃ products (99.7 wt%) were successfully prepared using a membrane extract-scrubbing-stripping-precipitate process. The economic evaluation of the process indicated that the production cost of lithium carbonate allows wide profit margin. The research showcased the feasibility of extracting Li⁺ from brine using the membrane extraction.