氨化法制备高纯二氧化硅及高纯石英的过程研究

发布时间：2018-04-09 07:38

  本文选题：氟硅酸　切入点：氨化反应　出处：《南昌大学》2016年硕士论文

【摘要】：氟硅酸是磷肥生产中的副产物,任其排放会污染环境,造成氟硅资源的浪费。利用氟硅酸,将其转化为高附加值的硅产品或氟产品有着良好的市场前景和环保意义。本实验以氟硅酸为原料,一步氨化反应得到氟硅酸铵溶液,设计铵盐钙盐除杂,得到净化的氟硅酸铵溶液,经过二步氨化反应得到产品高纯二氧化硅,然后高温煅烧高纯二氧化硅,制备了高纯晶体石英。对反应过程中的条件进行了探索和优化。制备氟硅酸铵溶液的最佳工艺条件为:一步氨化反应终点p H=3.8~4.0,氨水滴加速度1.5ml·min~(-1),反应温度25℃,搅拌速度200r·min~(-1),在此优化工艺条件下,氟硅酸铵得率93.6%。铵盐为添加剂调节氟硅酸铵溶液p H=6.5,溶液中的Ca金属杂质去除率达88.8%,Mg金属杂质的去除率达81.2%;钙盐为沉淀剂除杂,溶液中Fe去除率为82.3%,Al去除率达79.8%。除杂的最佳工艺条件:m(钙盐):m(H2Si F6折100%计)=9wt%,陈化40min,静置9h,最佳工艺条件下,去除了溶液中97.9%的金属杂质,得到了高纯的氟硅酸铵溶液,除杂效果理想。当m(钙盐):m(H2Si F6折100%计)=9wt%时,产品Si O_2中金属杂质去除率98.1%,杂质含量小于100μg·g~(-1),属于高纯二氧化硅,产品Si O_2纯度达到99.99%。制备高纯二氧化硅的最佳工艺条件:反应终点p H=8.5、反应温度40℃、氨水滴加速度4ml·min~(-1)。该条件下,高纯二氧化硅得率94.6%,粒径0.35μm。经由IR、TG检测,证明产品是Si O_2,XRD分析,产品Si O_2为非晶态;SEM分析,样品分散性良好,呈蓬松多孔状。高纯二氧化硅在煅烧温度高于1200℃时发生晶型转化,当温度达到1300℃,保温时间为2h时,无定型Si O_2转化为方石英晶体,转化率接近100%;晶化后样品的表面孔道消失,结构更为紧实;高温煅烧后,样品粒径减小,体积收缩,当煅烧温度达到1300℃,体积收缩率达81.89%。
[Abstract]:Fluorosilicic acid is a byproduct of phosphate fertilizer production, which will pollute the environment and cause waste of fluorosilicon resources.It has good market prospect and environmental protection significance to convert fluorosilicic acid into high added value silicon or fluorine products.In this experiment, ammonium fluorosilicate solution was obtained by one step ammoniation reaction with fluorosilicic acid as raw material. Ammonium salt calcium salt was designed to remove impurities, and purified ammonium fluorosilicate solution was obtained.Then high-purity silica was calcined at high temperature to prepare high-purity crystal quartz.The conditions in the reaction process were explored and optimized.The optimum conditions for preparation of ammonium fluorosilicate solution are as follows: end point of one-step ammoniation reaction (pH 3.8C), ammonia droplet acceleration (1.5ml min-1), reaction temperature 25 鈩，

本文编号：1725469