The Preparation Of Amorphous Silica And Its Applications In Organosilicon Synthesis By Microwave Irradiation

In this paper, the method of preparation of amorphous silica from serpentine and bentonite by sulfuric acid leaching in microwave field was investigated. The main factors that affect the leaching process of minerals, such as reaction time, microwave irradiation, the proportion of liquid to solid, the concentration of sulfuric acid and the particle size et al., were studied, and the optimum conditions of acid leaching were achieved. The structures of amorphous silica gained were characterized by XRD and its chemical compositions were analyzed. The acid leaching kinetics of serpentine was researched. The results showed that the leaching ratio of magnesia in serpentine and alumina in bentonite reached 97.7% and 97.1%, respectively; the chemical compositions of amorphous silica accorded with those of precipitated aqueous silica; microwave heating could remarkably increase the leaching rate, compared with the traditional heating methods, and the acid leaching kinetics of serpentine could be represented by volume reaction model, and the apparent rate expression was:In addition, coordinate organosilicon compounds have been directly synthesized by these obtained amorphous silica as silicon-contained materials in microwave field by atmospheric pressure distilling method. The structures of the resulting products were characterized by FTIR and XRD. The results showed that the products were pentacoordinate organosilicon compounds in alkali metals hydroxides and hexa-coordinate organosilicon compounds in alkaline-earth metals oxides, respectively.