Optimisation of crystallisation parameters for lithium carbonate microcrystals based on forward osmosis (FO) process

Abstract

Authors demonstrate the crystallisation of lithium carbonate (Li2CO3) microcrystals from brines of salt lakes using a forward osmosis (FO) process. In this FO process, FO is used to enrich the brine of the salt lake, and subsequently, Li2CO3 recovery in the form of microcrystal, while MD is used to recover the draw solution and extract clean water from the brine of the salt lake. The precipitates obtained in the hybrid process were verified to be Li2CO3 microcrystals owing to the lower saturation level compared to the other crystals comprising Li+, Na+, CO32 − , and Cl− in the saline water. An increased thickness of crystallised layer was observed on the anti-scaling FO membrane, which was strongly dependent on the surface energy of the surface, and the microcrystals were collected after a brief, simple membrane flushing using deionised water. By fine modification of the surface in a thin film composite (TFC) membrane with 3-(methacryloylamino)propyl-dimethyl-(3-sulfopropyl) ammonium hydroxide, polyethylene glycol, 2-(2,3,6-trifluorophenoxy)ethanol, the crystallisation rate on the surface was gradually reduced, while the crystal polymorphism was controllable from meta-stable α-form into stable γ-form. Results reported here highlight the potential and high efficiency of the FO process for crystallisation of Li2CO3 from brines of salt lakes.