Gas adsorptive properties of manganese dioxides

锰氧化物矿物在其表面吸附某些气体分子，并在加热时释放它们。用Q极质谱仪研究了天然和人工合成氧化锰矿物释放气体。在100-350 ℃、400-450 ℃和600-700 ℃的温度范围内观察到CO_2。在100 ~ 350 ℃范围内，CO_2的释放主要来自表面吸附。天然和人工合成的二氧化锰矿物对空气中的CO_2气体有很好的吸附作用，为了寻找新型的二氧化锰吸附剂，采用水热法还原γ-MnO_2制备了氢氧化锰矿物。将粉末状斜方锰矿和锰金属密封在具有水的Pt管中，并将其在150 ℃、1000 kb下保持10天。反应写如下。8MnO_2 + 2H_2O + Mn → 4Mn_2O_3（OH）+ MnO_2。添加金属锰以降低管中的氧气压力并将锰离子稳定为Mn^<3+>和Mn^<4+>。该产品的X射线粉末衍射图与斜方锰矿和水泥浆岩（γ-MnOOH）的X射线粉末衍射图非常相似。经Retveldt法细化后，其晶体结构与斜方长石和细浆岩等结构。产物的理想分子式为Mn^<3+>_2Mn^<4+>_2O_6（OH）_2。在还原过程中，出现斜方晶系+新相或新相+细晶。因此，很明显，ramsdellite和灌浆之间的固溶体是不存在的。

Manganese oxide minerals adsorb some kinds of gas molecules on their surface and released them on heating. The released gas from natural and synthetic manganese oxide minerals was studied by Q-pole mass spectrometer. CO_2 was observed in the temperature range 100-350 ﾟC, 400-450ﾟC and 600-700ﾟC. The released CO_2 gas between 100 and 350 ﾟC derived from the surface adsorption. Natural and synthetic manganese dioxide minerals adsorb CO_2 gas in the air readily.Manganese hydroxide mineral was synthesized by the reduction of ramsdellite (gamma-MnO_2) using hydrothermal techniques in order to find the new manganese oxide which adsorb CO_2 gas. Powdered ramsdellite and manganese metal was sealed in a Pt tube with water and keep it at 150 ﾟC, 1000 kb for 10 days. The reaction is written as follows. 8MnO_2 + 2H_2O + Mn -> 4Mn_2O_3(OH) + MnO_2. Manganese metal is added to reduce the oxygen pressure in the tube and stabilize manganese ion as Mn^<3+> and Mn^<4+>. The X-ray powder diffraction profile of the product is quite similar to that of ramsdellite and groutite( gamma-MnOOH). The crystal structure, refined by the Retveldt method, is isostructure to ramsdellite and groutite. The ideal formula for the product is Mn^<3+>_2Mn^<4+>_2O_6(OH)_2. In the process of reduction, ramsdellite + new phase or new phase + groutite is observed. Therefore it is obvious that the solid solution between ramsdellite and groutite is absent.