稀有金属冶炼高氟废水诱导结晶氟化钙的沉积特性及深度除氟研究

Due to poor defluorination efficiency and generate large volumes of sludge in the process of fluoride removal from precious metals refining wastewater with high levels of fluoride in Jiangxi Gannan, the precipitation properties of calcium fluoride by induced crystallization and depth defluorination from the point of crystallization chemistry will be studied in this project. The main contents include: the precipitation properties of calcium fluoride from precious metals refining wastewater with high levels of fluoride by coupling interaction of fluidized bed reactor and electromagnetic field will be studied, and the crystalline compounds formed by fluorine ion and other co-existing ions and their effects on crystallization thermodynamics of calcium fluoride and fluoride removal will be studied; the effects of waste water solution properties, crystal seeds added, and parameters of reactor under induction by coupling interaction of fluidized bed reactor and electromagnetic field on nucleation and growth rate, crystal size and the distribution of crystal in solution of calcium fluoride will be studied, the relation among environmental conditions, crystal structure and habit will be revealed, the special precipitation rule of calcium fluoride and chemical reaction kinetics of fluoride removal wil be explored, and the crystallization kinetics model of calcium fluoride will also be established；and then, experimental installation for precipitation of calcium fluoride on the principle of coupling interaction of fluidized bed reactor and electromagnetic field will be built, and the relationship between condition control and crystallization selection will be illustrated. These researchs can supply available data and approach for crystallization of calcium fluoride from precious metals refining wastewater with high levels of fluoride, realize depth defluorination and reuse calcium fluoride, and reduce environment pollution.

针对赣南稀有金属冶炼高氟废水除氟效果差、渣量大等问题，本项目从结晶化学角度，进行诱导结晶氟化钙的沉积特性及深度除氟研究。主要内容包括：研究流化床/电磁场诱导作用下稀有金属冶炼高氟废水氟化钙的沉积特性，系统研究氟离子与其它共存离子形成晶体化合物的类型，并研究其对氟化钙结晶热力学性质、除氟效果的影响；研究在流化床/电磁场耦合诱导下，废水溶液性质、晶种量、反应器参数等对氟化钙晶体成核及生长速率、晶体尺寸以及晶体在溶液中的分布的影响，揭示环境条件与诱导晶体结构组成、晶貌晶习的密切联系，探明诱导结晶作用下氟化钙析出的特殊规律及除氟化学反应动力学过程，建立氟化钙结晶动力学模型；最后构建流化床/电磁场作用下可能实施大规模的氟化钙结晶生长系统，阐明条件控制与选择结晶的相关关系。上述研究能为稀有金属冶炼高氟废水中氟化钙的高效结晶提供有效的基础数据和技术方法，从而实现氟深度去除和氟化钙资源化，减少环境污染。

赣南稀有金属矿产资源丰富，同时该地稀土冶炼企业也产生了大量高氟废水。稀有金属冶炼过程中产生的高氟废水存在着处理效果差、渣量大、沉降性差等问题尚未解决。针对这些问题，我们从结晶化学角度，进行了诱导结晶氟化钙的沉积特性及深度除氟研究，为氟化钙高效结晶提供了有利的基础数据、动力学依据和有效的技术方法。.首先，我们测量了氟化钙结晶的基础热力学数据，系统研究了不同条件下氟化钙结晶热力学参数，包括氟化钙结晶过程的溶解度、超溶解度以及介稳区，发现与自然条件下相比，共存离子、晶种、磁场及超声场的存在都对氟化钙结晶的热力学数据有明显的影响，结果表明晶种粒径为0.5-1 mm时，最有利于缩小氟化钙的超溶解度，加速氟化钙的沉积。其次，探明诱导结晶作用下氟化钙析出的特殊规律及除氟化学反应动力学过程，建立氟化钙结晶动力学模型，发现外场的存在有利于缩短氟化钙结晶的诱导期，促进氟化钙晶体的生长，同时不会改变氟化钙的晶体结构。.最后，构建了流化床诱导结晶装置，探究条件控制与选择结晶的相关关系，研究了不同晶种材料，粒径及质量对稀有金属冶炼高氟废水去除效率的影响。在最佳条件下，氟的去除率和回收率分别能达到93.79％和89.45％，回收的氟化钙的粒径约为1.5 mm左右。结果表明，流化床诱导结晶是一种绿色且经济可行的技术，实现了氟的深度去除和氟化钙高效资源化。