Sustainable Rice Straw Management Using Pyrolysis-Extraction Process Towards Value-Added Products

Abstract

Rice straw, one of the main agricultural wastes of north of Iran, was utilized for extraction of two valuable products: high surface area activated carbon (AC) and nano-silica powder. The positive effect of silica extraction from activated rice straw ash on the porosity of resultant AC was determined. It was found that the performance of K 2 CO 3 was better than KOH for producing highly porous AC (2356 m 2 /g) under less severe conditions (relatively low impregnation ratio=1.5). The sensitivity analysis for several operating conditions was carried out, and the optimal conditions to reach the highest surface area, pore volume and silica extraction yield were determined for each chemical agent using Taguchi analysis. Among the factors changed, the highest contributions belonged to the impregnation ratio and activation temperature; therefore, other factors were selected based on economic considerations. The average production yield of activated carbon and silica from raw rice straw in this work was calculated around 9% and 7%, respectively. The average particle size of silica powder was estimated by SEM (around 35 nm) and DLS tests (200-300 nm), and an acceptable BET surface area and pore volume of 250 m 2 /g and 1 cm 3 /g, respectively, were obtained for this product.