Experimental data of lignin recovery from coconut husk using response surface methodology (RSM) through thermal pretreatment process

This investigation examines the impact of low nitric acid concentration, temperature, and residue time on the recovery of lignin from coconut husk through a thermal pretreatment process under optimal conditions. Additionally, the RSM response surface methodology is employed to determine the optimal conditions for lignin recovery. The results of the statistical analysis of independent variables, including temperature, time, and nitric acid concentration, indicate that these parameters had a substantial effect on the recovery of lignin. The ANOVA analysis indicates that all independent parameters and the model were statistically significant at the 95% confidence level. The current study's results demonstrated that the highest lignin recovery yield was 85.31%. This was achieved by processing coconut under optimal conditions, which included a low nitric acid concentration of 0.010 M and a temperature of 200 °C for 30 minutes. Furthermore, the thermal pretreatment procedure resulted in the complete conversion of the crystalline cellulose present in the coconut husk to an amorphous form, as demonstrated by the scanning electron microscope (SEM) analysis. Meanwhile, the crystallinity index of solid residue following thermal pretreatment demonstrated a substantial increase of 76.65% in comparison to that of native coconut husk (64.12%). Nevertheless, the lignin that is recovered is utilized as a precursor for the production of high-value products. Consequently, it is crucial to implement a thermal pretreatment process in order to enhance the efficiency of the chemical conversion process.