Silicon dioxide extraction from cashew nut ashes

Abstract

After the cashew nuts processing, the husks rich in silicon are used as fuel in boilers where they are burned at temperatures above 1000 °C. In this study, it was investigated a form of silicon extraction from the ashes taken from the boiler using a chemical route. At first, the ashes were bathed with an aqua regia solution (HCl + HNO₃), then it were bathed with sulfuric acid (HѕSO4) and taken to the oven at 600 °C for two hours. After the heating process it were made analyzes of X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF). The results of XRD indicated the presence of approximately 45% of silicon on the samples and the results of the XRF indicated that most of the element was in the form of crystalline oxide SiO2. It can be concluded that is possible to purify the ashes to use a waste of cashew nuts processing industry as a source of obtaining silicon dioxide in quartz format.