Study On Controlled Synthesis And Characteristic Of Porous Structure Manganese Oxide

Based upon manganese oxide octahedral [MnO6] of Layered Manganese Oxides was used as the primitive structure, the design and controlled synthesis of porous structure of OL、OMS manganese oxides and ML copper and manganese mixed oxides were investigated. Powder XRD, SEM and TEM were applied to characterize the as^-synthesized samples of OL、OMS and ML copper and manganese mixed oxides .The effects of the additional metals doping, cations and anions in mother solution on the crystallization of OL manganese oxides and reversible transformation were investigated. A new and convenient method to distinguish tunnel and layered structures after the ammonia leaching was proposed.By the redox reactions between Mn²⁺ and MnO4^-, the Octahedral layer structure （OL） manganese oxide were synthesized, during which Mg²⁺、Ni²⁺ and Co²⁺ were used as the directing agent. The sequence of directing of different cations additive was Mg²⁺>Ni²⁺>Co²⁺, however it was failed to get OL Manganese Oxides by synthesizing hausmannite that Cu²⁺ or Al3+ was introduced into the original Mn²⁺ solution as the directing agent. The type of anion did not change the mode of crystallization of OL Manganese Oxides but to certain extent influenced crystallization, structure and phase transformations. Such as the effects of anions on the crystallization of OL depended on the cations that were located in the interlayer. The sequence of crystallization rate of Birnessite by which Mg²⁺ , Ni²⁺ or Co²⁺ were used respectively as directing agent in the original Mn²⁺ solution were Ac^->Cl^-/NO3^->NO3^->Cl^-, Cl^-/NO3^->Cl^->NO3^->Ac^- and NO3^->Cl^-/NO3^->Cl^->Ac^- .The Octahedral layered structure （OL） manganese oxide were synthesized by the reaction between Mn²⁺ and KMnO4 mixed with NaOH, in which Mg²⁺, Ni²⁺, Co²⁺, Cu²⁺ or Al3+ was used as the directing agent. The sequence of directing of different cations additive was Mg²⁺>Ni²⁺>Co²⁺>Cu²⁺>Al3+. The effects of anions on the crystallization of OL depended on the directing agent. The sequence of crystallization of Birnessite by which Mg²⁺ , Ni²⁺, Co²⁺ or Cu²⁺ were used respectively as directing agent in the original Mn²⁺ solution were Ac^-≈Cl^-/NO₃^->Cl^->NO3^-, Cl^->Cl^-/NO₃^->Ac^->NO₃^-, Ac^->NO₃^-≈ Cl^-/NO₃^->Cl^- ,and Cl^-/NO₃^->Cl^->Ac^->NO₃^-.The Octahedral layered structure （OL） manganese oxide was synthesized by O₂ oxidation in alkali medium. The effects of O2 flow rate was the significantly influencing factors for the formation of layered manganese oxides. The other factors address slight effect on the formation of layered manganese oxide with some influence on the crystallization and size of layered manganese oxide. It was proved that O₂ flux was over 5L/min for 5h were indispensable for the formation of Buserite, which were transferred to Birnessite after drying. However the pretreatment of the reacting solutions by N2 and the dried atmosphere had little effect on formation of Buserite.The reversible transformation between Birnessite and Buserite lied on the types of cations in the interlayer. Only in the presence of Mg²⁺ in the original Mn²⁺ solution with KMnO4 used as oxidant can make Birnessite translate into Buserite. It is depended on the Mg²⁺ ions in the interlayer could interact strongly with surrounding water molecules. The optimum conditations for the reversible transformation are dried temperature of 40℃, hydrated time of 24h.The Cu^-ML and Cu^-OMS^-1 copper and manganese mixed oxides had been hydrothermally synthesized by using the layered Buserite as precursor. The Buserite was synthesized by O2 oxide in alkali medium. It was proved that ammonia leaching can effectively distinguish tunnel and layered structures. XRD analyses had revealed that the diffraction peaks of Cu^-OMS^-1 did not change after the ammonia leaching. This suggested that the tunnel structure of OMS^-1 is maintained. The interlayer distance of Cu^-ML decreases considerable and the composition is Birnessite manganese oxides after the ammonia leaching.