重镁水中通入空气制备三水碳酸镁晶须

Preparation of Nesquehonite Whiskers Through Bubbling Air into Magnesium Bicarbonate Solution

以轻烧白云石为原料,通过碳化法制得重镁水（Mg（HCO3）2）溶液,进而向重镁水中通入空气获得了三水碳酸镁（MgCO3·3H2O）晶须。采用X射线衍射、扫描电子显微镜和热重分析对制得的样品进行表征,研究了影响重镁水分解率和三水碳酸镁晶须形貌的因素。结果表明：提高分解温度、增大空气流量、增加晶种加入量和延长分解时间,都可促进Mg（HCO3）2的分解;分解温度30℃、空气流量60 L/h、晶种加入量8%、通气时间12 h时,Mg（HCO3）2的分解率为89.85%;当温度升高到60℃时,Mg（HCO3）2的分解时间由12h降至2.5 h,分解率为91.26%。所得的三水碳酸镁都为棒状,且其长径比随着温度的升高而降低,60℃时获得的三水碳酸镁的长度为40~80μm,长径比为6~15;三水碳酸镁在96.8℃开始分解,480℃时分解完全,质量损失率为70.91%。

Magnesium bicarbonate solution was firstly prepared by a carbonation method with a light burned dolomite powder as a raw material, and then magnesium bicarbonate solution is bubbled with air to synthesize nesquehonite whisker. The parameter influences on the decomposition rate of magnesium bicarbonate solution and the morphology of nesquehonite were investigated. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy and thermo-gravimetry, respectively. The results show that increase of decomposition temperature and time, air flow, and addition amount of seed crystal all can promote the decomposition of Mg（HCO3）2. The decomposition rate of Mg（HCO3）2 is 89.85% at the temperature of 30 ℃, the air flow rate of 60 L/h and the seed crystal amount of 8% and the ventilation time of 12 h. When the temperature increases to 60 ℃ at certain air flow and amount of seed, the decomposition time of Mg（HCO3）2 decreases from 12 to 2.5 h, leading to the decomposition rate of 91.26%. The morphology of nesquehonite is rod shape, and the length-diameter ratio decreases with increasing the temperature. The length of nesquehonite is 40-80 um, the length-diameter ratio is 6-15 at 60 ℃. The decomposition of nesquehonite occurs at 96.8 ℃, and the decomposition completes at 480℃ , resulting in that the sample loss mass is 70.91%.