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

Abstract

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.