Optimization of Hemicellulose Recovery from Rice Straw for Biorefinery: Dilute Acid Pretreatment at Reduced Temperatures

Dilute sulfuric acid pretreatment was conducted to extract hemicellulose from rice straw at reduced temperatures (<100 °C), and the process was optimized using experimental design analysis with the response surface methodology. Fourier Transform Infrared Spectroscopy analysis was performed to verify the purity of recovered hemicellulose. Central composite design of experiments (DOE) was applied to develop a statistical model to identify the main effects and interaction effects of process parameters: acid concentration, reaction temperature, and reaction time. The proposed quadratic model showed a high adjusted determination coefficient (0.91) and Fischer's test value (22.4), indicating that the model is adequate to characterize the relationships among the process parameters and explain the variation observed in response. Acid concentration and reaction temperature have significant first order and quadratic effects on hemicellulose recovery. However, reaction time exhibited only a significant quadratic effect on hemicellulose recovery. The maximum hemicellulose yield (15.78%) was obtained at optimal conditions of 0.26 moldm−3 acid concentration, 98.1°C reaction temperature, and 30.48 min reaction time. In addition, residual analysis was carried out to check the adequacy of the proposed model.