Optimization of Dilute Sulphuric Acid Pretreatment Of Cotton Stalk Through Box Behnken Design of Response Surface Methodology

Abstract

The purpose of the current study was to use diluted sulfuric acid to optimize the pretreatment conditions for cotton stalk. Different quantities (w/v) of cotton stalk (5%, 10%, 15%) were pretreated with different concentrations of H2SO4 (0.6%, 0.8%, 1%) for 4, 6 and 8 hours to degrade the crystalline structure of cellulose and to facilitate the hydrolysis of the cellulosic component. Dilute acidic pretreatment was also conducted in steam conditions at 121 °C, 15 psi. A statistical model was created using a three-level Box Behnken design (BBD) to optimize the process variables. Maximum results regarding cellulose exposure (85%) were recorded with 15% substrate loading, 0.8% acid concentration and time period of 8 hours followed by steam. Maximum total phenolic compounds (8.17 mg/mL) were observed under the same conditions, except steam. The effectiveness of the pretreatment was also analyzed by FTIR and XRD techniques. The results were analysed using ANOVA with a second order polynomial equation. The P value 0.05 showed the significance of the model. The pretreatment conditions that allowed obtaining maximum cellulose content can be used for enzymatic hydrolysis to produce maximum sugars.