Electrochemical Desalination and Recovery of Lithium from Saline Water upon Operation of a Capacitive Deionization Cell Combined with a Redox Flow Battery

Abstract

With the drastic growth in the demand for lithium, recovery technologies that remove Li ions from a brine solution are attracting more interest. In this field, capacitive deionization (CDI) has been suggested in various studies because it is energy efficient, economical, and environmentally friendly. These selective processes, however, have not been accompanied by desalination, which is a nonselective process by which salt ions are removed from the brine. In this work, a new-concept system has been designed for the simultaneous desalination and recovery of Li from the brine, in which the two different ion-exchange membranes separate the two electrochemically active spaces of desalination and lithium recovery. It is originally based on the combination of a redox flow battery (RFB) and CDI. The CDI cell has been sandwiched between two electrodes of a RFB, which has been operated and desalinates the brine simultaneously with the charging step of the RFB. In addition, an ion sieve (λ-MnO 2 ) has been utilized in the anolyte tank of the RFB cell, which selectively captures the lithium ions during desalination in CDI and charging in RFB. This combined system has been operated successfully with good desalination performances along with high selectivity in lithium-ion capture.

Electrochemical Methods for Water Purification, Ion Separations, and Energy Conversion

“…Ions constitute a major subset of contaminants found in water. When present even at low concentration, ions like F – , CrO 4 2– , AsO 4 3– , Hg 2+ , and Pb 2+ can pose a threat to the health of humans and animals. − For this reason, researchers have studied and developed platforms for targeted removal of ionic contaminants using CDI. − Selective adsorption by CDI can also be employed to recover valuable elements, such as lithium, − phosphorus, − and nitrogen. ,− In this section, we briefly review several experimental works that focus on selective separation of ions from multicomponent solutions using porous carbon electrodes. In particular, we focus on studies that involve either two monovalent ions or one monovalent and one divalent ion, and we exclude studies that involve mixtures of more than two competing ions because of the complexity of these systems. − We then discuss the quantification of ion selectivity via a separation factor.…”

Developmental Progress of Electrodialysis Technologies and Membrane Materials for Extraction of Lithium from Salt Lake Brines

“…This method is suitable for the extraction of lithium from low-grade brines with a high Mg 2+ /Li + mass ratio. The adsorption materials for lithium include lithium manganese oxide (LMO) and lithium titanium oxide (LTO) ion sieves, as well as lithium/aluminum layered double hydroxide (Li/Al LDH). − …”

Comparison of Ion Selectivity in Electrodialysis and Capacitive Deionization

“…69 The higher Na Li + + with such intercalation electrodes is largely due to the smaller Li + ionic diameter in crystal form, as Li + is 1.2 Å and smaller than the 1.9 Å of Na + . 56,116,117 Several other selectivity mechanisms relevant to ED and CDI have been studied as a means to perform this separation, including Na + selectivity due to its smaller hydrated diameter, 49,118 chemical affinity of Li + toward chemical groups in the ED CEM, such as a LiCo 0.5 Mn 1.5 O 4 spinel type adsorbent, 82 and intercalation CEMs, such as Li 0.33 La 0.56 TiO 3 . 119 We also tabulate in Figure 2 selectivity is not achieved by either ED or CDI, likely due to its much larger hydrated diameter of 7.6 Å compared to 6.6 Å of Cl − .…”

“…Using such cathodes boosts Li + selectivity when compared to achieved using a CDI cell with porous carbon electrodes . The higher with such intercalation electrodes is largely due to the smaller Li + ionic diameter in crystal form, as Li + is 1.2 Å and smaller than the 1.9 Å of Na + . ,, Several other selectivity mechanisms relevant to ED and CDI have been studied as a means to perform this separation, including Na + selectivity due to its smaller hydrated diameter, , chemical affinity of Li + toward chemical groups in the ED CEM, such as a LiCo 0.5 Mn 1.5 O 4 spinel type adsorbent, and intercalation CEMs, such as Li 0.33 La 0.56 TiO 3 …”