Removal of lithium from aqueous solutions using halotolerant bacteria from El Salar del Hombre Muerto

Abstract

The interaction of lithium with halotolerant microorganisms was evaluated to determine its effect on bacterial isolates and its removal from the surrounding environment. The observed effects on bacterial cells included different biomass production, exopolysaccharide synthesis, variation in morphology, and spore formation under the presence of Li. They allowed microorganisms not only to tolerate 20-30 g/L LiCl but also to remove it from the surrounding environment. The microbial-metal interactions were verified through lithium removal from the growth medium and also from aqueous solutions using fresh cultures. Interestingly, in presence of LiCl, bacteria from the genus Bacillus sp. (strains FAMB1, SA313, HX11, and HA120a) produced similar amounts of biomass and higher amounts of exopolysaccharides in comparison to the condition without LiCl added. These isolates, except for FAMB1, were also efficient in Li removal in all the evaluated conditions, removing around 30% of initial Li during growth and 50% from aqueous solutions. Furthermore, fresh cultures of Micrococcus luteus SA211, Bacillus sp. FAMB1, Micrococcus sp. M12, Brevibacterium sp. SX139 and Kocuria sp. SA129b removed Li from the aqueous solutions, and only SA129b released the metal back to the solution after incubating for 6 h. Finally, Bacillus sp. HX11, Bacillus sp. HA120a, Kocuria sp. SA129b and Brevibacterium sp. SX139 developed an efficient and environmentally-friendly removal of lithium from aqueous matrices in short periods, showing specific lithium removal values between 1.0 and 1.4 mg Li/g cells.