硅砂表面多孔SiO2包覆层的构建及其富集废水中离子用于玻璃的着色与诱导析晶

Absorbents can effectively remove hazardous ions from waste water. However, the used absorbents and the ions adsorbed therein finally turn into solid waste and another source of pollution. In this project, we are going to construct porous silica coating on the surface of silica sand, which is the main raw material for glass production. The route for the construction of the porous silica coating layers will include coating the silica sand with water glass followed by acid treatment, in-situ polymerization of silanes or the hydrolysis and condensation of silicon alkoxides on the surface of the sand. After the surface functionalization of the pores, the coated silica sand will be applied in removing hazardous ions from waste water. Then, the used sand absorbents will be collected and applied in the preparation of glasses. In the meantime, hazardous ions will turn into colorants and nucleating agents for the production of color glasses and bulk-nucleated glass-ceramics and can be permanently immobilized in the chemically stable glasses. By this way, the pollution of some ions in waster waters could be solved quite consummately. The research will mainly focus on the development of methods and media for coating silica sands with porous silica layers. The influences of the modification of silica sands on their filtration performance and on the glass batch preparation as well as the glass melting process will be investigated. The behavior and mechanism of ion adsorptions by the modified silica sand from waste waters will be studied. The colorization or inducing crystallization effects of Cr, Cd, Co, Cu, Ni, Ti, F or[PO4]3- ions which are adsorbed on the modified silica sands will be evaluated and summarized. The results will provide new ways for the modification of silica sand as well as theoretical guidelines for the reutilization of disposed silica sand absorbent and the application of hazardous ions from waste water in the glass colorization and induced crystallization.

吸附剂可有效脱除废水中有害离子，但吸附剂连同其吸附的离子又成为固体废弃物污染源。项目拟以生产玻璃的最主要原料硅砂为基础，通过水玻璃包覆结合酸处理、硅烷原位聚合、硅醇盐水解缩聚等途径在硅砂表面构建多孔SiO2包覆层，对孔表面进行功能化修饰后用于富集废水中有害离子。回收的硅砂作为玻璃原料，同时废水中有害离子转化为颜色玻璃及微晶玻璃所需的着色剂和晶核剂，并永久固化于化学稳定性高的玻璃中，较完善地解决废水中一些离子的污染问题。重点研究硅砂表面多孔SiO2包覆层的构建方法与体系、改性硅砂的过滤性能及其作为玻璃原料对配合料制备与熔化的影响、改性硅砂富集废水中有害离子的行为、机理；评估从废水中富集的Cr、Cd、Co、Cu、Ni、Ti、F、[PO4]3-等离子使玻璃着色或发生诱导析晶的效果，总结其一般规律。研究结果将提供硅砂改性新方法，为废硅砂吸附剂的再利用及废水中离子用于玻璃着色和诱导析晶提供理论指导。

吸附剂可用于废水的净化处理，其使用方便，成本较低；使用过的吸附剂可经过反冲或化学洗提后有限次地再利用，但吸附能力下降，终将连同其吸附的有害物质一起变为固体废弃物而形成二次污染源，成为业界的一大难题。本项目通过精心设计具有特征成分与结构的吸附剂，在有效净化废水的同时，实现废吸附剂及其吸附离子的固化及再利用。实验指出四种玻璃生产用硅砂在碱性条件下的水热溶解液作为制备多孔SiO2的硅源具有普适性；发明了三种方法使用不同的硅源在硅砂表面构建多孔SiO2包覆层，并对孔表面进行氨基功能化修饰，获得比面积是原硅砂数十至数千倍、吸附金属离子能力大幅提升的包覆及改性硅砂，分析了影响包覆层形成与表面积的因素及包覆层的形成机理；将改性硅砂用于静态或动态吸附水中（包括Cr3+, Cr6+, Cu2+, Cd2+, Ni2+, Co2+，Zn2+及Cr3+与Cu2+、）及实际废水中的有害离子（Cr6+、Fe3+/Cu2+），取得良好效果，详细研究了pH、初始离子浓度、吸附剂用量、吸附温度及时间、流速对改造后硅砂吸附水中不同离子的影响，分析了吸附等温线及动力学模型。因硅砂本身在水处理中广泛应用，因此改造后的硅砂易在现有水处理的工艺及条件下使用。另一方面，表面含多孔SiO2包覆层及硅烷改性的硅砂不会向玻璃中引入杂质成分，颗粒等物性也未有明显改变，因此完成过滤废水任务的废弃的硅砂吸附剂仍可作为玻璃原料再利用，同时，其从废水中富集的有害离子就可转化为颜色玻璃的着色剂，如利用从实际废水中富集的六价铬离子制得啤酒瓶所需的翠绿色玻璃，从水中吸附的铜镍钴离子制得湖蓝、棕色和天蓝色玻璃；所得玻璃的光谱曲线与使用传统着色剂时一致，实现了项目的最初设想，为解决吸附法净化废水产生废吸附剂的问题提供了全新的思路。采用氨基功能化的表面含多孔SiO2包覆层的硅砂成功用于电镀铜废水的处理，并采用处理完电镀铜废水的废吸附剂再用于吸附水中的氟和磷，实现了双重净化效果。吸附的磷和氟有助于降低玻璃析晶温度，但吸附的磷和氟量较低，对促进玻璃整体析晶的效果仍有待提高。