Mn-kaolinite synthesis under low-temperature hydrothermal conditions

Abstract Mn-kaolinite was hydrothermally synthesized, for the first time, using silicic acid, Mn-carbonate and aluminum nitrate mixed with aqueous solutions of KOH at 100–200 °C for 24–96 h. Without the addition of Mn-carbonate to silicic acid and aluminum nitrate mixture, no crystalline material could be synthesized by hydrothermal treatment up to 200 °C for 6 days. However, by the addition of Mn-carbonate to the above precursors, Mn-kaolinite was synthesized at both 100 and 200 °C for 1 or 2 days, indicating that Mn played an important role in the formation of kaolinite. At a reaction temperature of 100 °C, the Mn-kaolinite peaks became sharper with increasing reaction duration, as expected.