Lithium Carbonate and By-products Recovery via Membrane Electrolysis: Practical Considerations in Bringing an Idea Closer to Industrial Implementation

FLEXER, VICTORIA; MARÍA LAURA VERA; CÉSAR H. DÍAZ NIETO; WALTER R. TORRES; MATÍAS A. MATA; NADIA C. ZEBALLOS; CAMILO J. O. PALACIOS; NOELIA A. PALACIOS; EVA CAROLINA ARRUA

Mar del Plata

Congreso; 34th Topical Meeting of the International Society of Electrochemistry; 2023

International Society of Electrochemistry

Lithium salts are fundamental raw materials for the production of rechargeable batteries, which are in turn closely linked with a much wider penetration of both electric vehicles and renewable energies in our energy matrix. The technology currently in use for lithium salts recovery from continental brines entails the evaporation of huge water volumes in desertic environments. It also requires for the native brines to reside not less than a year in open air ponds, and is only applicable to selected compositions, not allowing its application to more diluted brines such as geothermal or produced waters from the oil industry.We have proposed an alternative technology based on membrane electrolysis, schematized in Fig. 1. In three consecutive water electrolyzers, fitted alternatively with anion and cation permselective membranes, we have showed, at proof-of-concept level, that it is possible to sequentially recover lithium carbonate and several by-products, including magnesium and calcium hydroxide, sodium carbonate, H2 and HCl[1-3]. The big challenge is to bring this technology closer to practical implementation. For example, in order to produce 20,000 tonnes of lithium carbonate yearly, from a brine with 700 ppm Li+, about 20,000 m3 of brine will need to be processed daily. Thus, the issue is how to apply relatively well-known electrochemical technology principles to large volumes and to a highly complex and saline broth.I will discuss our latest results in attempting to solve some of the challenges in this concept[4]. The first big challenge is how to avoid solid formation within the electrolyzers compartments (see Fig. 1). The second challenge is to find the optimal current density. In classic electrochemical engineering, higher current density is most often associated to higher operational costs, and concomitant reduction of capital costs for a given production capacity. In our system, because of the high salinity of the feed, there is a strong interplay between osmosis and electroosmosis. The relative migration rates of the different monovalent cations are also affected by the current density. Thirdly, the permselective membranes are subjected to extreme pH values and thus their integrity needs to be monitored, while their selectivity towards anions/cations can be modified. Finally, while higher by-product purity is desired, it is most important to avoid Li+ ions entrapment during solid formation.