Rice straw is a waste product from rice manufacturing that contains cellulose (32–47%), hemicellulose (19-27%), lignin (5–24%), and ash (13–20%). The ash form consists of a large percentage of silicon dioxide (SiO2) with widespread use in the industrial field. The extraction of silicon dioxide has been conducted using the sol-gel and ashing method combined with the leaching process using an acid solution such as hydrochloric acid (HCl) at a concentration of 3%. In using HCl with a concentration of 3%, impurities are often found in the SiO2 sample. Therefore, this study uses the leaching method with HCl of several variations (3%, 5%, and 7%). By raising the concentration of HCl in this process, the quality of SiO2 without impurities is increased. The results indicate that increasing the concentration of HCl can significantly lower the sample’s impurity content. In the 3% treatment, impurities were found in the form of Carbon and Calcium. The treatment obtained no impurities using 5% and 7% HCl concentrations. As a result, the highest purity of SiO2 obtained was 89.31% in the 5% HCl treatment. The sample treated with 5% HCl was in the semiconductor region and exhibited an amorphous structure.

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