Bio-templated synthesis of lithium manganese oxide microtubes and their application in Li+ recovery

Highlights: • Biogenic birnessite was used to synthesize microtube-type Li+ ion sieve. • The biomineral facilitates LMO formation at a lower temperature. • HMO-MT with high Li+ uptake capacity was obtained. • Temperature effects on properties of HMO-MTs were studied. -- Abstract: Microbial transformations, a primary pathway for the Mn oxides formation in nature, provide potential for material-oriented researchers to fabricate new materials. Using Mn oxidizing fungus Paraconiothyrium sp. WL-2 as a bio-oxidizer as well as a bio-template, a special lithium ion sieve with microtube morphology was prepared through a solid-state transformation. Varying the calcination temperature from 300 to 700 °C was found to influence sample properties and consequently, the adsorption of Li+. Lithium manganese oxide microtube (LMO-MTs) calcined at different temperatures as well as their delithiated products (HMO-MTs) were characterized by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Calcination temperatures affect not only the content but also the crystal structure of LMO spinel, which is important in Li+ adsorption. The optimized sample was obtained after calcination at 500 °C for 4 h, which shows higher Li+ adsorption capacity than particulate materials