Studies on deacidification of fumed silica with hot air

摘要

Deacidification of fumed silica under different temperature, time, with or without steam have been measured. The surface properties such as number of silanol groups, BET surface area, and morphology of particles have been investigated. The results showed four interesting and interrelated phenomena: (1) It is very easy to be obtained a satisfactory pH value if fumed silica is treated under the tempture above 250 deg C in a few minutes, which due to the easily evaporated property of the halogen. (2) The reaction of silanol with OH~(-1) could be examined by the difference of pH value before and after silica addition in a solution. (3) Up to the temperature of 600 deg C, the agglomerate of fumed silica become smaller with the increasing of temperature or time. (4) When steam is added during the deacidification process, there are more silanols on the surface with the increasing of the steam amount. The agglomerates are a bit larger than those of the fumed silica under the same condition except for without steam. But they are still smaller than the agglomerates of untreated fumed silica. BET surface area has no obvious change during these processes, which mean no sintering occur.