Octamethylcyclotetrasiloxane Interaction with Lithium Ions

Lithium, for battery use, is in demand globally. Lithium recovery usually relies on brines. In some parts of the world where lithium and other metals, mining for these metals are contaminating water systems that lead out to the ocean. The brine-based extraction could be improved by using octamethylcyclotetrasiloxane (D-4) is a crown ether analog containing silicon atoms. The molecule is a partial negatively charged ring able to bond to a positively charged metal ions (e.g. Li+) Specifically, we report that Li+‘fits’ in the D-4 ring, and that D-4 extraction could recover lithium from brines, the Salton Sea or the ocean. Our main focus is examining D-4 sequestration of Li+at different concentrations (1M LiCl in deionized water and at decadal concentrations below that). D-4 sequestering of Li+ was confirmed by NMR and AA Emission Flame test. D-4 29Si NMR signals at 35.56, 6.02, -18.50, -34.87, and -84.89 ppm were used to find the differences in concentration trends AA flame test was to find out the difference in the concentration of aqueous Li+ions between before and after D-4 interaction. D-4 interacting with Li+at higher concentrations of LiCl in deionized water presented a greater difference in 29Si NMR chemical shifts than lower concentrations. When AA emission test of aqueous solutions, higher concentrations of Li+were tested first before adding D-4. After interaction with D-4, the counts did not reveal a significant change. This result may be related to the fact that lithium has a very strong emission profile. At lower Li+concentrations, there was a marked difference in counts of pre- and post-interaction with D-4