Study On The Surface Modification And Dehumidification Behavior Of Silica

In this dissertation, the process of hydrophobic modification and the mechanismof filter cake dehumidification were studied using precipitated silica as subjectinvestigated. The main research work includes:(1) In aqueous system, taking activation grade as the main index, cetyl trimethylammonium chloride (CTAC) was chosen as the more appropriate modifier for wetsurface modification of silica and the modification conditions were investigated viasingle-factor experiments. The optimum condition was obtained as following: thesystem pH8, the modifier dosage2%, the modification time40min, themodification temperature60°C and the ratio of silica to solvent9:100. Threerepeated experiments under the optimum conditions showed that the averageactivation grade of silica reached99.77%.(2) The original and modified silica were characterized respectively by Fouriertransform infrared spectroscopy, X-ray diffraction, Zeta potential, particledistribution analyzer, Transmission electron microscopy and so on. The resultsshowed that: the modified silica has the same crystal type as the original silica, butthe modified silica has pretty higher lipophilicity when the particle surfacesuccessfully coated by CTAC.(3) The dehumidifying agent were introduced into the filtration system of silicato study the dehumidification behavior. Using Taking the water content of silicafilter cake as the main index, the OP-10was chosen as the more appropriatedehumidifying agent. The dehumidifying conditions were investigated viasingle-factor and orthogonal experiments, and the optimum condition was obtainedas follows: the pH value8, the concentration of the dehumidifying agent400ppm,the reaction time12min, the stirring speed400r/min and the temperature70℃.Repeated experiments under the optimum condition showed that the water contentof silica filter cake reduced from71.02%to56.69%, meanwhile the filtration rateof silica slurry increased.(4) Pilot study on the dehumidification mechanism of the silica was carried outbased on surface tension, foaming properties, wetting contact angle andflocculation of silica. From the analysis, we concluded as follows: the dehumidifying agent can reduce the surface tension of the solution but can notsurely reduce the water content of silica filter cake. OP-10contributes to theflocculation and enlarging of the wetting contact angle of the silica filter cakewhile its foaming characteristics may deteriorate the dehumidifying effect on thesilica filter cake in some degree.