Process optimization of microwave-assisted alkali pretreatment for enhanced delignification of Prosopis juliflora biomass

This study reports on the delignification of Prosopis juliflora biomass using microwave-assisted alkaline pretreatment. Response surface methodology was employed to analyze the effect of process variables on delignification. Four independent process variables such as microwave irradiation power (270-450 W), microwave irradiation time (3-5 min), alkali concentration (0.75-1.25% wt/vol) and liquid to solid ratio (LSR; 10-20 mL/g) were analyzed. A second-order nonlinear equation was developed to validate the model. The experimental results suggested that all the variables exhibited a similar response. The developed model was statistically valuated using analysis of variance. The optimum conditions determined from the study were as follows: microwave power of 360 W, irradiation time of 4.40 min, alkali concentration of 1.24% wt/vol and LSR of 13.16 mL/g. Maximum delignification of 75.12% was obtained using microwave-assisted alkali pretreatment method. The delignified Prosopis juliflora biomass was characterized using scanning electron microscopy and Fourier transform infrared spectroscopy studies. It was confirmed that microwave-assisted alkali pretreatment for a short duration facilitated maximum removal of lignin from biomass. The present study, therefore, helps in developing a suitable strategy both for satisfying the energy need and management of the exotic weed.