Optimization of Lignin Content Reduction in Date Palm Fibers by Response Surface Methodology and Desirability Function

During the past decade, the use of plant fibers for reinforcing biocomposite material has attracted many researchers. The lignin content of the fibers reduces the mechanical properties of the resulting biocomposites, thus the lignin content is reduced by chemical treatments. In this research, the effective factors in the process of lignin reduction, including hydrogen peroxide and sodium hydroxide content, and temperature of the medium and the retention time, were optimized to prepare fiber with lowest amount of lignin and with highest tensile strength. The experiments were performed based on "central composite rotatable design" using four independent factors, each at five levels. A second degree polynomial was used to define a function relating the dependent and independent variables. The experimental data and the predicted data by the models were highly correlated (R2 <0. 98). The optimization results indicated that the optimized level for hydrogen peroxide and sodium hydroxide were 4. 5% and 5. 7%، wt. The optimum medium temperature and retention time were 41. 9ºC and 16. 8 h, respectively. At the optimized values of the independent variables, the lignin content and the tensile strength of the fibers were 10. 23% ww and 220. 08 MPa, respectively.