Abstract:

Forward osmosis (FO) is a sustainable liquid mining process that can be used to concentrate metal-containing aqueous solutions with minimal energy input and allow the recovery of valuable metals. It relies on a semi-permeable membrane to allow the selective and spontaneous permeation of water from a low-concentration feed solution into a high-concentration draw solution. In this work, we report on the application of FO in the liquid mining of lithium from an emulated lithium brine lake using non-toxic aqueous inorganic draw solutions. A flat-sheet cellulose triacetate (CTA) membrane was used to study the effects of the type (NaCl, CaCl₂, and MgCl₂,) and initial concentration (1, 2, and 3 M) of the draw solution on the final lithium concentration in the feed solution. After running a series of experiments, the concentration of lithium was increased by more than 3.5 times after 1 h, while MgCl₂ as a draw solution showed the highest water flux (4 L/m²/h). Overall our results indicate a strong potential for FO in liquid mining applications: the concentration of dilute solutions containing critical and strategic metals, which due to their low concentration cannot be recovered.

Keywords: Liquid mining; Forward osmosis; Lithium; Brine lake concentration.

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Mr. Afshin Amani