RESPONSE SURFACE OPTIMISATION OF COTTON FIBRE ACETYLATION FOR OIL SORPTION USING CENTRAL COMPOSITE DESIGN

Abstract: Acetylation enhances the hydrophobicity of lignocellulosic biomasses by replacing their dominant hydrophilic hydroxyl groups with hydrophobic acetyl groups, thereby increasing their suitability for oil sorption. This modification typically results in weight gain due to the higher molecular mass of the introduced functional groups. This study employed the Central Composite Design (CCD) Response Surface Methodology (RSM) to optimise cotton fibre acetylation to enhance its weight percent gain (WPG) and improve its suitability for oil sorption. Reaction time, temperature, and the fibre mass-to- volume ratio of acetic anhydride were investigated, with WPG as the response parameter. Among the 20 experimental runs, the highest weight gain of 4.782% was achieved at 2 hours, 137°C, and a mass- to-volume ratio of 0.011 (0.550 g/50 ml). However, optimisation of the experimental conditions yielded a predicted WPG of 4.950% at 2.584 hours, 129.964°C, and 0.258 g of fibre per 50 ml of acetic anhydride. Validation of the predicted optimum response resulted in an experimental WPG of 4.896%, closely matching the predicted value of 4.950%. The minimal deviation of 0.054 demonstrated the model's high accuracy and reliability. Additionally, the desirability score of 1.000 indicated that the optimised conditions perfectly aligned with the study’s objectives. Successful acetylation was confirmed through FTIR analysis, which provided evidence of the introduction and enhancement of peaks associated with acetylated products.