一种制取无水氟化铝的新工艺

New technology for preparation of aluminum fluoride

利用磷肥副产物氟硅酸与廉价的高岭土代替氢氧化铝和资源相对缺乏的萤石来制取氟化铝。实验证明浸取工艺的最佳工艺条件为:高岭土中w(Al2O3)为26%～30%,氟硅酸中w(H2SiF6)为21%～28%,浸取温度为80～100℃,浸取时间控制在10min,控制反应终点pH在1～4。第一次结晶时要加入生成量的20%～25%(质量分数)氟化铝做晶种,同时为降低结晶后成品中铁含量,在结晶前加入硫代硫酸钠调整至无Fe3+存在。氟化铝的结晶温度在95℃左右,结晶时间为5h是最佳反应条件。此法既降低了生产成本,又解决了磷肥厂的环保压力,具有一定的社会效益和经济效益。

Hydrofluorosilicic acid, by-product of phosphate fertilizer production and low cost kaolin ware applied to substitute aluminum hydroxide, and relatively deficient fluorite resource to produce aluminum fluoride. Experiments showed the optimum leaching process conditions： A1203 of kaolin was 26% - 30% （mass fraction） , H2SiF6 of hydrofluorosilicic acid was 21% -28% ,leaching temperature was 80- 100℃ ,leaching time was 10 min and pH of reaction terminal was at 1 - 4. Aluminum fluoride with 20% - 25% of the generated product should be added at the first crystallization as seed crystal. Meanwhile, to reduce iron content of finished product after crystallization, sodium thiosulfate was added into the solution be- fore crystallization to eliminate Fe^3＋ . Crystallization temperature and crystallization time controlled at about 90 ℃ and 5 h respectively, were the best reaction conditions. This method not only reduces the cost of production but also releases the environmental pressure of phosphate fertilizer plant. Therefore,it has a certain social and economic-benefits.