Master of Science

thesisLithium is an important metal for energy storage applications. With the increase in demand for lithium in the near future, it is important to explore low-grade brine resources, which contain the majority of known lithium resources. In this work, λ-MnO2 diatomaceous earth composite adsorbent is synthesized by using a combination of hydrothermal treatment and solid-state calcination. The synthesized adsorbent was tested with LiCl buffered solution for various batch adsorption parameters. Loading of 28-29% λ-MnO2 on diatomaceous earth showed the best performance for lithium adsorption. The adsorption was found to follow the Langmuir isotherm model and pseudo second order kinetics model. The thermodynamic state functions indicate that lithium adsorption is endothermic in nature involving O-H bond breakage. It is also observed that there is a 30% loss in adsorption capacity after five adsorption-desorption cycles, when hydrochloric acid is used as an eluent due to Mn2+ loss. Replacing acid with (NH4)2S2O8 as an eluent at 80 oC increases the recycling stability of the adsorbent by decreasing Mn loss. The adsorbent is tested with Great Salt Lake water and 95% of lithium is extracted with high selectivity (for example, the separation factor of lithium over Mg is 23,043) from the brine over alkali and alkaline earth metals