Synthesis of biogenic Mn oxide and its application as lithium ion sieve

Geomimetics, taking lessons from nature's biogenic mineralization mechanisms, can provide powerful tools for advancing biohydrometallurgical processing. Microbial transformations are largely responsible for the Mn oxides found in nature. In this research biogenic birnessite was produced by a manganese-oxidizing fungus, Paraconiothyrium sp. WL-2, at pH 6.5 under room temperature, and characterized by XRD and TG-DTA. Abiotic (chemically synthesized) acidic birnessite was also prepared hydrometallurgically and subjected to a similar battery of characterization techniques. Following thermal treatment the sorption characteristics of these two materials were compared. The biogenic precursor showed several advantages to produce more effective Li-ion sieve than the chemically synthesized precursor. First, a shorter calcination period was required to produce Li4Mn5O12 without other phases; second, a greater content and higher crystallinity of H4Mn5O12 were obtained from the biogenic precursor. These advantages might be caused by poorer crystallinity and around 20 wt% organic matter in biogenic birnessite. While sorption density of Li+ in mmol/g was basically dependent on contents of H4Mn5O12 phase, the unique morphologies and sorption density were maintained with biogenic precursor even after repetition of sorption/desorption of Li+.