由低品位菱镁矿制备高纯碳酸镁的研究

以低品位菱镁矿为原料, 经轻烧、消化, 在不同条件下进行碳酸化, 将消化料浆转化为碳酸氢镁进入液相而制得重镁水, 采用活性炭为吸附剂脱除钙、铁等杂质, 并研究了不同添加剂对重镁水热解产物形貌的影响。研究表明, 随着碳酸化温度升高, 氧化镁的收得率降低; 随着碳酸化时间的延长, 氧化镁的收得率增加; 随CO₂气体流量的增大, 氧化镁的收得率稍有增加, 但增加幅度很小。XRD分析表明重镁水热解产物的主要成分是3MgCO₃·Mg(OH)₂·3H₂O 和MgCO₃·3H₂O。经过提纯处理后, 热解产物纯度很高, CaO含量小于0.04%, TFe含量小于0.02%。SEM分析表明, 无添加剂时, 热解产物为片状; 加入酸性添加剂磷酸二氢钾时, 热解产物为花瓣状; 加入碱性添加剂碳酸铵时, 热解产物为球状; 加入可溶性镁盐时, 热解产物为晶须状。

Preparation of High-purity Magnesium Carbonate from Low-grade Magnesite

Mg(HCO3)₂ solution was prepared by light burning, hydration, and carbonation treatment at different condition with low-grade magnesite as raw material, then impurities were removed by using activated carbon as adsorbent. The effect of different additives on the morphology of pyrolytic products from Mg(HCO₃)₂ solution was studied. Results showed that the yield rate of the caustic calcined magnesia was significantly reduced as the hydrous carbonation temperature increased, while the carbonation time was extended, the yield rate of the caustic calcined magnesia was increased. It increased a little with the increase of CO₂ flow rate. The XRD result showed that the main components of Mg(HCO₃)₂ pyrolytic products were 3MgCO₃·Mg(OH)₂·3H₂O and MgCO₃·3H₂O, containing less impurities, for example, content of CaO was lower than 0.04% and TFe was lower than 0.02%. SEM results showed that the morphology of magnesium carbonate was highly dependent on the preparation conditions. A flake-like pyrolytic product was obtained without any additive. Petal-shaped pyrolytic product was prepared with additive of potassium dihydrogen phosphate. Spherical pyrolytic product was obtained with additive of ammonium carbonate, and whisker pyrolytic product was obtained if soluble magnesium salt was added.