白云石制备的纳米氢氧化镁的性能及其影响因素

PARAMETER EFFECTS ON PREPARATION OF NANOSIZED PARTICLES OF MAGNESIUM HYDROXIDE FROM DOLOMITE AND THEIR CHARACTERS

探讨了白云石碳化法制备纳米级氢氧化镁的工艺条件,研究了沉淀剂、反应温度对纳米级氢氧化镁形貌的影响,以及表面活性剂对纳米级氢氧化镁分散性的改善,并对反应机理进行了阐述。结果表明:以氨水为沉淀剂所得的纳米氢氧化镁近似六边形的薄片状,平均粒径为16nm,其结构稳定性优于以氢氧化钠为沉淀剂的产品。当反应温度为30℃时,Mg(OH)2形成细小晶核,薄片的厚度为5～7nm,晶粒粒径为10～15nm;反应温度为50℃时,晶核开始生长为大晶粒,但排列无规则;反应温度为70℃时,Mg(OH)2薄片的厚度增至10nm左右,晶粒粒径为10～20nm,具有规则排列的完整晶粒;反应温度为80℃时,Mg(OH)2晶粒具有不规则排列。加入表面活性剂聚乙二醇或十二烷基硫酸钠可以提高纳米粒子的分散性。当表面活性剂聚乙二醇用量为氢氧化镁的3.0%(以质量计,下同)时,纳米氢氧化镁的分散性最好,片层的厚度约为10nm,平均粒径为20nm。当表面活性剂十二烷基硫酸钠用量为氢氧化镁的4.0%时,纳米氢氧化镁具有较好的分散效果,平均粒径为20nm。

Parameter effects on the preparation for nanosized particles of magnesium hydroxide from dolomite via carbonation were investigated. The effects of precipitator and reaction temperature on the morphology of the nanosized particles were evaluated. The improvement of surface active agent on the dispersion of the particles was analyzed. The reaction mechanism of the experiment was discussed. The results show that the crystallization of magnesium hydroxide using ammonia as a precipitator is better than that using sodium hydroxide as a precipitator, and the nanosized particles of magnesium hydroxide appear an approximately thin sheet of hexagons with an average particle size of 16 nm. The smaller crystal nuclei of magnesium hydroxide with the thickness of about 5–7 nm and the size of 10–15 nm could be prepared at the reaction temperature of 30 ℃. The crystal nuclei started to grow larger with the disordered arrangement at 50 ℃. The integrated crystalline grains of magnesium hydroxide with the thickness of about 10 nm and the size of 10–20 nm could be prepared at 70 ℃. However, the irregular arrangement could occur at 80 ℃ . In addition, the dispersion of the nanosized crystalline grains of magnesium hydroxide could be improved by using polyethylene glycol （PEG） or sodium dodecyl sulfate （SDS） as surface active agents. Then the thickness of the nanosized particles is 10 nm. The dispersion performance became superior at an optimized amount of PEG of 3.0%. The dispersion was more efficient at the amount of SDS of 4.0% and its size is 20 nm.