含镍磁黄铁矿硝酸浸出液中硝酸镁与硫酸镁的分离

THE CRYSTALLIZATION SEPARATION OF MAG NESIUM SULPHATE AND MAGNESISIUM NITRATE IN NITRIC ACID LEACHING SOLUTION OF NICKEL-BEARING PYRRHOTITE

硝酸催化浸出是处理金属硫化物的有效方法。用这种方法在较低温度和氧压下成功地处理了含镍磁黄铁,但矿石中的氧化镁与硫酸和硝酸反应生成硫酸镁和硝酸镁,后者消耗了大量硝酸;因而需要分离硫酸镁,返回使用硝酸镁才能保证浸出过程经济地进行。本研究测定了Mg(NO_3)_2-MgSO_4-H_2O系在343K,308K,以及Mg(NO_3)_2-MgSO_4-C_2H_5OH-H_2O系在298K的平衡相图。结果表明,蒸发结晶法及乙醇结晶法均能有效地分离出硫酸镁,但后者更为节能。加10％乙醇即可使硫酸镁与硝酸镁较好分离。

As an effective method for digesting metal sulfides, the catalytic leaching with nitric acidin sulphate system has been used to treat nickel-bearing pyrrhotite successfully at much lower tem-perature than that of high oxygen pressure leaching. In this process, magnesium oxide will react withsulphuric acid and nitric acid to form magnesium sulfate and magnesium nitrate. The latter willconsume a large volume of nitric acid if it is not separated from magnesium sulfate and recovered. In this research, the phase equilibriums of Mg(NO_3)_2-MgSO_4-H_2O system at 343K, 308K and ofMg(NO_3)_2-MgSO_4-C_2H_5OH-H_2O system at 298 K have been studied. According to the phase diagramsobtained, the separation of Mg(NO_3)_2 from MgSO_4 has been discussed in details. The results indi-cate that evaporation and alcohol crystallization are both effective in separating pure magnesiumsulfate from magnesium nitrate. Furthermore, alcohol crystallization results in savings on energy.Addition of 10% ethanol to a Mg(NO_3)_2 and MgSO_4 solution results in an almost complete cry-stallization of magnesium sulfate.