微波快速合成钙锰矿的影响因素

Influencing factors of the synthesis of todorokite by microwave radiation

以通O2氧化Mn(OH)2制备的水钠锰矿为前驱物,采用微波加热合成钙锰矿,并探讨微波的功率、反应温度、时间和pH值等条件对钙锰矿形成的影响。结果表明:一定微波条件下可快速合成粒径均一、结晶度较好的钙锰矿。当微波辐照功率大于150 W时,随着微波功率升高,合成钙锰矿所需时间缩短,600 W功率下20min即可快速得到钙锰矿;温度越高合成钙锰矿所需时间也越短,体系温度为100℃时不能生成钙锰矿,但升高到140℃时,20min即可合成出钙锰矿;在酸性条件下合成钙锰矿的转化率低,而中性和碱性条件下钙锰矿的形成速度快、转化率高、结晶度好。

Todorokite was synthesized through microwave heating from a layer structured precursor buserite prepared by 02 oxidation of Mn（OH）2. The effects of several synthesis parameters under microwave heating including microwave power,temperature,time and the initial pH on the phase transformation from buserite to todorokite were investigated. The results showed that the well-crystalline and uniform sized todorokites were obtained under microwave heating conditions. Todorokite could not be synthesized under 150 W power of microwave radiation. The reaction time of synthesizing todorokite decreased with the increase of microwave power. Todorokite could be obtained in 20 minutes with 600 W of microwave radiation. The higher the temperature for synthesizing todorokite, the shorter the reaction time required. Todorokite could not be obtained at 100 ℃, nevertheless it could be synthesized in 20 minutes when the temperatue reached 140 ℃. In acidic medium, the formation rate of todorokite was low and poor-crystalline phase was produced. Whereas in neutral and alkaline medium, the formation rate of todorokite was high and well-crystalline phase was obtained.