Sono-assisted sulfuric acid process for economical recovery of fermentable sugars and mesoporous pure silica from rice straw

Abstract

The present study was focused on the successive recovery of reducing sugars and pure silica from rice straw using ultrasound-sulfuric acid process. The effect of sonication time (10-60 min), liquid to solid ratio (7-10), and acid concentration (7.5-10%) was investigated. Maximum sugar yield (310 g/kg dry biomass) was achieved at 80 degrees C, 10% H2SO4, 60 min and liquid to solid ratio 7. Sono-assisted sulfuric acid process efficiently removed metal oxides from the rice biomass. The residual biomass was combusted at 750 C for 15 min to produce white silica. Analyses revealed that white silica possessed mesoporous structure with 166.03 m(2)/g specific area, and a purity of 96% (wt.%). Thus, ultrasound-sulfuric acid process followed by short thermal treatment could produce high sugar yield and pure silica. This approach may not only facilitate solid waste management but it may also reduce the overall cost of bioethanol production to make it cost competitive with fossil fuels. (C) 2013 Elsevier B.V. All rights reserved.