Hydrothermal synthesis of Mn-kaolinite using NaOH or KOH and characterization

Mn-kaolinite containing both Mn and Al in the octahedral sheet was prepared under hydrothermal conditions of 100–200 °C for 6–96 h by using Al-nitrate, Mn-carbonate, silicic acid and aqueous solutions of NaOH or KOH. The synthetic phases were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray Absorption Near Edge Structure (XANES) spectroscopy. The results showed that the best hydrothermal conditions to prepare well-crystallized Mn-kaolinite were 100–175 °C for 2 days using either NaOH or KOH and the Mn species was mostly present as Mn3+ as determined by XANES spectroscopy.