Study On Dissolving Silicon Powder By Hot Alkali And Preparation Of Silica Aerogel

Micro silicon powder is widely used in the industry of cement, concrete, refractory, metallurgical and so on, because of its stable physical and chemical properties. At present, the most serious problem is that the micro silicon powder contains high content of impurities. And it will seriously impact on the recycling of resources. In order to solve this problem,we should develop efficient method to remove the metal impurities of micro silicon powder, and prepare high purity silica products, and improve the added value of micro silicon powder so that we can achieve the goal of making full use of the resources.By useing micro silicon powder as silicon source. By adjusting the acid types, concentration, temperature, solid-liquid ratio, reaction time and other factors in the process, and choosing the best condition to remove the metal impurities efficiently, and reduce the influence of metal impurity in the dissolution process. It is concluded that the suitable acid leaching conditions:HCl as leaching solution, concentration was 2mol/L, reaction temperature was 60, solid-liquid ratio was 1:6¹:8, the reaction time was 40⁶0min.In order to realize the thermal process of alkali soluble Si O₂ reinforcement by acid leaching removes the metal impurity. At the beginning of the alkali dissolution process, when the micro silicon powders are dealed with the acid leaching, the initial dissolving rate of micro silicon powders can be improved from 46.62% to 61.91%, and silica dissolution rate increased obviously.By adjusting the carbonization process of concentration of sodium silicate, carbonization process ventilation, ventilation rate of CO₂, temperature, the species and amount of additive, and the concentration and dropping speed of sulfuric acid in the process of sulfuric acid precipitation to analyze the morphology of the impact with the change of ion concentration in the solution in the process of producing silica hydrated.Through the study of the components of micro silicon powder sample analysis?XRF?, phase analysis?XRD?, particle morphology?SEM?, the impurity distribution analysis?SEM, EDS? we can determine the content of the impurities and the microcosmic distribution. The filtrate of experiment is measured with the method of chemical analysis to confirm the extraction yield of metal ions in the process of acid leaching and the changing of ion concentration in the carbonization process.This study is to solve the main problem that the low dissolution rate in the process of hot alkali dissolving Si O₂, and improve the utilization chances of micro silicon powder. By measuring the ion in the process of carbide precipitation changes and morphological changes, in order to discuss the mechanism of the synthesis of silica,and improve the preparation technology of silica aerogel.