Enhancement of Rice Straw Biodegradability by Alkaline and Acid Thermochemical Pretreatment Process: Optimization by Response Surface Methodology (RSM)

The solubility of rice straw in alkali, Sodium Hydroxide (NaOH) and Potassium Hydroxide (KOH), and acid, Sulfuric Acid (H2SO4), pretreatment process were optimized by response surface methodology (RSM). Laboratory-scale experiments were carried out in a reflux completely mixed reactor with 500 mL capacity. The reaction temperature, stirring time and chemicals concentration are three chosen parameters for achieving to optimum solubility of rice straw. The experimental data were evaluated statistically by the analysis of variance (ANOVA). The maximum solubility of 82.40% was obtained in 200°C, 180 min and 0.6 g NaOH /g waste. The efficiency of NaOH in rice straw solubilization process is around 35% higher than KOH and around 77% higher than H2SO4. As a main result, NaOH pretreatment appears to be the most effective method in hydrolysis of rice straw compared with KOH and H2SO4 reagents. Also, the RSM is a reliable tool to the optimization of rice straw solubility process.