用青海盐湖水氯镁石电解制取镁新方法的基础研究

Qinghai province has plenty of magnesium and potassium resources. Every year, potassium fertilizer is produced with the by-product of bischofite. At present, bischofite cannot be used and is discarded. This cause not only the waste of resources, but also the formation of magnesium harm for the biological environment .Recently, it is in the period of the formation of bischofite in the district of discharging bischofite. The cost of mining is low. Comprehensive utilization of bischofite is emergent. This project proposed a combined process of comprehensive using bischofite: preparation of magnesia with ammonia-direct electrolysis of magnesia. This process produces magnesium with the by-product of magnesia..This project prepared magnesium hydroxide by precipitating magnesium ion. Magnesia can be obtained by calcinating magnesium hydroxide. The optimal parameters in the preparation of magnesia are obtained. The optimal reacting time is 20min.The molar ratio of magnesium ion and ammonia is 1:1.2,The magnesium ion content is 45g·l -1and the reacting temperature 55℃.The magnesia with 99.5% of purity was obtained by the comprehensive experiment. The recycling rate of magnesium of from bischofite is 80%.The characters of this process are the high purity, the high recycling rate and the low cost by recycling ammonia..A new technique of direct electrolysis magnesia was investigated in the laboratory. The NdCl3-MgCl2 binary system was adopted in experiments. The chief chemical and physical properties of molten system including melting point, conductivity, and density, solubility of magnesia and soluble behaviors of magnesia in the NdCl3-MgCl2 binary system are obtained. The investigation shows that solubility of magnesia is 11% in the centigrade temperature from 650℃ to 850℃.The supporting electrolyte from the NdCl3-MgCl2 binary system is practical. The influence of current density, electrolytic temperature and density deference on the current efficiency on carbon anode was studied. When the NdCl3 molar fraction is 0.4 and the centigrade electrolytic temperature 700℃,the current efficiency is 90%,the energy consumption is 11.5kW·h/kg Mg and carbon dioxide is discharged on carbon anode. This new technique has low energy consumption, high current efficiency and less pollution for the environment..This aim of this project is to propose an optimal solution of the comprehensive utilization of magnesium resources of Qinghai salt lakes and to provide refractory materials of high purity. This will have profound influence on the present production of magnesium. This new process avoids the difficulty of bischofite dehydration and save energy consumption by 20~30%.Carbon dioxide is obtained on carbon anode, which is beneficial for the environment. The importance of this investigation is not only in the comprehensive utilization of the magnesium resources of Qinghai salt lakes but also in the profound influence on the present magnesium electrolysis process..

青海盐湖储量巨大的水氯镁石由于脱水制备镁电解原料无水氯化镁十分困难而尚未利用。本研究运用稀土化学、熔盐化学、计算化学、电化学和物理化学开展交叉综合研究，建立以水氯镁石常规脱水制备的含氧化镁无水氯化镁为原料，稀土催化氧化镁溶解－电解制取镁的新原料、新方法。新方法高效、清洁并且成本低，对青海盐湖水氯镁石的利用意义十分重大。.