A modified oxidation-deprotonation reaction (ODPR) was developed to synthesize wellcrystallized birnessite. We compared the conventional methods for synthesis of birnessite with the ODPR approach. The structural chemistry of birnessite was evaluated by highresolution transmission electron microscopy (HRTEM), using an energy-dispersive spectrometer (EDS) to determine the Na + content. The average oxidation states (AOS) of birnessite were determined by potentiometric titration. Infrared spectrometric (IR) and X-ray diffraction (XRD) analytical techniques were used to characterize birnessite. The HRTEM lattice image and low Na + content suggest that there are no vacancies in the octahedral layers of birnessite. The AOS values of birnessite ranged from 3.77 to 3.87 and the presence of IR bands at 1153 and 1084 cm -1 were attributed to the Mn 3+ -OH deformation. The results show evidence for the presence of the Mn 3+ or Mn 2+ in the structure of birnessite.

Lithiophorite is a naturally occurring phyllomanganate which has been identified in soils and ores. Studies on a synthetic version have shed light on the conditions required for the formation of lithiophorite. In this study, we successfully prepared lithiophorite under highly alkaline conditions. In addition, we found that Li + , Al 3+ and hydrothermal treatment are all necessary for the formation of lithiophorite. Lithiophorite, birnessite and Li-intercalated gibbsite were examined by infrared (IR) spectroscopy. The Mn oxide sheets of lithiophorite and birnessite were found to have quite similar structural environments. On the other hand, the LiAl 2 (OH) 6 sheets are affected more markedly by the Mn oxide sheets. After intercalation, the symmetry of the six interlayer OH groups of LiAl 2 (OH) 6 is reduced and they are divided into two groups occupying different sites, corresponding to the IR absorption bands at 3480 and 3312 cm À1 , respectively.

Layered double hydroxides (LDHs) are known as 'anionic clays'. They comprise a class of material with positively charged octahedral double hydroxyl layers and exchangeable anions. The Li/Al LDH term includes a group of LDHs with Li/Al octahedral double hydroxyl layers. We have demonstrated a modifed method, using Li/Al LDH-OH (OH- as interlayer anions) as the starting material, for preparing Li/Al LDH-X (X represents interlayer anions, including dioctyl sulphosuccinate (DOSS), dodecyl sulphate (DDS), mercaptoacetate (MA), EDTA, Tiron and dichromate) under mild acid conditions (pH in the range 4 to 5). However, in the case of acid-sensitive anions, Fe(CN)(6)(4-), Li/Al LDH-Fe(CN)(6)(4-) can be prepared by a two-step procedure using Li/Al LDH-DOSS or similar compounds as intermediates to react with acid-sensitive anions under mild alkaline conditions (pH approximate to 9)

Lithiophorite consists of alternatively stacked MnO6 octahedral sheets and LiAl2(OH)6 octahedral sheets. Its applications in laboratories and industries have been hindered by sophisticated operation procedures, long reaction time, or impurities existing in the final product. We proposed a fast and simple method, mixing birnessite, aluminate and lithium hydroxide together (designated it as the BAL method) in high alkaline conditions (pH > 13), and treating it hydrothermally at 423 K for 6 hours to prepare pure lithiophorite. A specific reaction between lithium cations and aluminate anions plays as a key role in the BAL method. Due to this specific reaction, Li x Al n (OH) m +z complexed cations can form and penetrate into interlayers of birnessite to replace sodium cations. In high alkaline conditions (pH > 12), Li xAln(OH)m +z complexed cations become smaller and are soluble. Thus, the higher alkaline Li x Al n (OH) m +z complexed cations can penetrate into interlayers of birnessite at a higher rate. Furthermore, impurities, such as lithium intercalated gibbsite (LIG), aluminum oxyhydroxides and aluminum hydroxides are not stable in high alkaline conditions. Consequently, pure lithiophorite can be easily obtained within 6 hours in high alkaline conditions.