添加剂对六水氯化镁制备氧化镁及氧化镁水化产物的影响

Effect of Additives on the Preparation of Magnesium Oxide with Magnesium Chloride Hexahydrate and Its Hydration Products

为解决盐湖镁资源的大规模利用问题,以盐湖六水氯化镁为原料,分别添加硫酸镁、氯化钠和氨水,考察不同添加剂与用量对煅烧制备MgO的影响,并进行水化反应得到不同形貌的氢氧化镁。利用XRD、SEM、激光粒度分析检测方法对MgO及其水化产物进行表征。结果表明:引入SO_(4)^(2-)使六水氯化镁溶液的pH降低,不利于MgO的生长,融合为大颗粒形貌。Na^(+)与SO_(4)^(2-)相比,对六水氯化镁制备MgO的破坏程度强。Na^(+)使MgO的晶粒尺寸变大,特征粒径达D50=28.69μm,畸变程度变差,制备的MgO水化后仍存在未完全水化的MgO,衍射峰I001/I101的值为0.723,(101)生长面显露得更多,导致六方片层变厚,产物相互粘结,片层堆积。引入氨水后,当其添加量(物质的量之比)为0.2时,可制备片状形貌的MgO,特征粒径D50仅为1.78μm。MgO水化时,产物全部转化为Mg(OH)2,I001/I101的值为0.777,结晶完整,呈六方片穿插的花簇状,为其在吸附净化等领域提供了潜在的应用前景。

In order to solve the problem of large-scale utilization of magnesium resources in salt lake,magnesium sulfate,sodium chloride and ammonia were added from salt lake as raw materials.The effects of different additives and dosages on the preparation of magnesia were investigated.Magnesia hydroxide with different morphology was obtained by hydration reaction.Magnesium oxide and its hydration products were characterized by XRD,SEM and laser particle size analysis.The results showed that the introduction of SO_(4)^(2-)reduced the pH of magnesium chloride hexahydrate solution,which was not conducive to the growth of magnesium oxide,and fused into large particle morphology.Compared with SO_(4)^(2-),Na^(+)has stronger damage degree to MgO preparation from magnesium chloride hexahydrate.Na^(+)increased the grain size of the product magnesium oxide,the characteristic particle size reached D50=28.69μm,and the degree of distortion became worse.There were still incomplete hydrated MgO after hydration of the prepared MgO,the ratio of diffraction peak I001/I101 was 0.723,and the growth surface of(101)was more exposed,resulting in the thickening of hexagonal lamellae and the products sticking to each other and lamellar accumulation.When the molar ratio of ammonia to magnesium chloride hexahydrate is 0.2,magnesium oxide with flake morphology can be prepared,and the characteristic particle size is only D50=1.78μm.In the application of MgO hydration,all the products are converted to Mg(OH)2,the ratio of I001/I101 is 0.777,the crystal is complete,and the flower cluster is interspersed with hexagonal pieces,which provides a potential application prospect in adsorption purification and other fields.