华中科技大学硕士学位论文蛇纹石制取高纯氧化镁的研究姓名:袁灿申请学位级别:硕士专业:无机化学指导教师:高中洪20090524摘要氧化镁是一种用途很广的化工原料,工业上氧化镁的生产依据初始原料(菱镁矿、白云石、水镁石、蛇纹石、卤水等)的不同其生产方法也不同。
蛇纹石由于其资源丰富、镁含量较高及自身结构特殊,近年来利用其制取氧化镁、二氧化硅及其他附带产品的研究得到了重视。
然而利用蛇纹石制取氧化镁存在工艺复杂,原料消耗量较大,成本高,尾液难以回收,易造成环境污染,沉镁率不高,杂质离子,特别是钠离子包夹于碱式碳酸镁中难于洗去等问题。
因而本文对蛇纹石酸浸滤液的精制除杂以及沉镁工艺条件做了比较全面的探讨,旨在提高氧化镁产品的纯度,提高沉镁率,从而提高经济效益。
在酸浸滤液精制除杂方面,采用空气氧化酸浸滤液中的二价铁,减少了双氧水的用量。
简化了精制过程,采用NaOH调节pH值,沉淀Fe3+、Al3+等,Na2S沉淀Ni2+和其他重金属离子,一次除杂尽量除尽各杂质,过硫酸铵二次氧化进一步除杂(Mn2+、过量的Na2S)并作为保险措施控制除杂质量。
在沉镁方面,比较全面地比较了不同沉淀剂沉镁的效果。
从沉镁率、原料消耗、过滤难易情况考虑,通过试验对比,确定了最佳的沉淀剂为氢氧化钠-纯碱,其中n NaOH︰nNa2CO3为2︰8。
另外探讨了利用氢氧化钠或纯碱沉镁过程中钠包夹于碱式碳酸镁中的问题,并通过优化工艺条件,减少了钠的包夹,进一步提高了氧化镁的纯度。
这些研究给蛇纹石制取氧化镁,特别是高纯氧化镁的生产工艺过程改进及工艺条件的选择提供了一定的参考。
关键词:高纯氧化镁 蛇纹石 除杂 沉镁 沉淀剂AbstractMagnesium oxide is one of the most widely used chemical materials. Industrial production of magnesium oxide has different methods which based on the initial raw materials (magnesite, dolomite, brucite, serpentine, brine, etc.). Serpentine, because of its abundant resources, a higher magnesium content and its own special structure, in recent years, making use of its magnesium, silica and other ancillary products has became a hot spot. However, there are some problems in the production of magnesium oxide with serpentine, such as process complexity, greater consumption of raw materials, high cost and difficulty in the end liquor recovery, causing environmental pollution, low sedimentation rate of magnesium, impurity ions, especially sodium ion, being wrapped in the inside of m agnesium subcarbonate, which is difficult to wash away. So in this paper we represent a relatively comprehensive discussion on the purification of the serpentine acid abstraction and the magnesium precipitation conditions, which aimed at improving the purity of magnesium oxide products, increasing the magnesium precipitation rate, thereby improving economic efficiency. On the purification of the serpentine acid abstraction, air oxidation of ferrous ion in the acid abstraction was used for the first time, to reduce the consumption of hydrogen peroxide. The refining process was simplified: adjusting the pH with NaOH, precipitating Fe3+, Al3+, etc., Na2S precipitating Ni2+ and other heavy metal ions, removing a variety of impurities at a time, then ammonium persulfate was used for further oxidation (Mn2+, excessive Na2S) and as a quality insurance measure to control the impurity content. Considering the magnesium precipitation rate, raw materials consumption, ease of filtration, it was found that sodium hydroxide-sodium carbonate was the best precipitant, and the ratio of the two was 2:8. In addition, to further enhance the purity of the magnesium oxide, the problem of sodium ion being enwrapped inside of the magnesiumsubcarbonate was also been discussed, and by optimizing the process conditions, this situation was greatly improved. These studies give a reference, to a certain extent, to the preparation of magnesium oxide with serpentine, especially to high-purity magnesium oxide production.Key words:high-purity magnesium oxide serpentine purification magnesium precipitation precipitant独创性声明本人声明所呈交的学位论文是我个人在导师指导下进行的研究工作及取得的研究成果。