Silica extraction from integrated refinery of rice straw for production of value-added products

Rice straw is an agricultural residue from rice production, which can be a potential lignocellulosic feedstock for various value-added products. In this study, silica was extracted from the rice straw. The biomass was pre-treated with ethanol and was cooked with 18% w/w sodium hydroxide to extract lignin and silica. The silica was precipitated from the alkaline solution using 30% sulfuric acid to pH 11.5 and was recovered through centrifugation. The obtained solid was washed and then combusted at 575 °C for 6 hours. The obtained ash was dissolved in sodium hydroxide solution at pH 8.0 and then re-precipitated by sulfuric acid to form silica powder, which obtained a yield of about 6.7% w/w dry rice straw. The characteristics of amorphous disk-formed silica, determined using XRD, SEM, EDS, and FT-IR.