Determination of Silicon Content in Metallurgical-Grade Silicon Refined Slag using Two-Step Dissolution Chemical Analysis Method

Abstract Under the demand of global green and low-carbon development, it is urgent to recycle silicon from metallurgical-grade silicon refined slag (MGSRS). Content of elemental silicon (Si) in MGSRS is the key of silicon recovery, and directly affects the selection and economic value of the silicon recovery technology. In this study, a two-step dissolution chemical analysis method is proposed to separate and determine the silicon and other silicon phases content of MGSRS. First, the silicate in the MGSRS was dissolved by hydrochloric acid to obtain the silicate content, and mixed particles containing silicon and silicon carbide (SiC) were separated. Second, silicon was dissolved by a mixture of nitric and hydrofluoric acid (HF/HNO₃), and the SiC particles were separated, then the Si and SiC content were determined respectively. During the two steps, the dissolution effect and repeatability of silicate and silicon with different acid was studied. Finally, The silicon content in MGSRS measured by the two-step chemical method was 21.84±0.53%, under the condition of volume ratio of HNO₃:HF is 1:1 and reaction time is 1h. This method breaks the situation that the content of elemental silicon in MGSRS is estimated only by experience. It has a positive impact on the further development of silicon recovery from MGSRS and can reduce environmental pollution.