高温改性对硅藻土结构及过滤性能的影响

Effects of high temperature modification on structure and filtration properties of diatomite

研究升温时间、改性温度及保温时间对硅藻土助滤剂白度及过滤性能的影响规律,结合扫描电子显微镜观察硅藻土的孔洞变化,采用X线荧光衍射及傅里叶红外光谱分析硅藻土助滤剂物相变化规律,并对影响机理进行探讨。研究结果表明:对于临江硅藻土,升温时间为3.00 h、改性温度为1 000℃、保温时间为1.50 h的改性条件可获得过滤性能最佳的助滤剂产品。适度延长升温和保温时间以及提高改性温度,有助于硅藻土白度及过滤性能的提高,但会促进蛋白石转化为对人体健康有害的晶型方石英;高温下助熔剂金属离子会部分破坏蛋白石中Si—O—Si结构,并使其在冷却中重组为方石英的六元环结构,改性热能的提高使金属离子更活跃,故形成更多的方石英。

The effects of heating time, modified temperature and heat preservation period on the whiteness and filtration performance were investigated. The changes of diatomite pores were observed by scanning electron microscopy （SEM）. The phase changes of diatomite filter aids were studied by X-ray diffractometer （XRD） and Fourier transform infrared spectroscopy （FT-IR）, and the mechanism of them was explored. The results show that diatomite filter aids obtained in the conditions of heating time of 3.00 h, modified temperature of 1 000 ℃ and heat preservation period of 1.50 h have the best filtration properties for the Linjiang raw diatomite. The appropriate long heating time, high temperature or long heat preservation period are beneficial to the whiteness and filtration performance, but more crystal cristobalite which is harmful to human is generated from opal. The metal ions from the flux are believed to partially break Si—O—Si chains of the opal at high temperature and then be recombined to a hexatomic ring mesh structure of cristobalite during the cooling process. More cristobalites appear after higher thermal energy is provided, because they can make the metal ions more active.