Application of box–behnken design–based response surface methodology optimization for predicting lignin residue following microwave-assisted inorganic salt (NaCl) pretreatment of Napier grass

Abstract

ABSTRACT Microwave irradiation is an effective pretreatment method for lignocellulosic biomass. Microwave-assisted inorganic salt (MAIS) pretreatment was employed to treat Napier grass (Pakchong 1) (Pennisetum purpureum) under different conditions to break down lignin from cellulose and hemicellulose in plant cell walls. Lignin and hemicellulose content were investigated under different NaCl concentrations (0.0, 1.0, and 2.0 M), and microwave irradiation was performed at 300, 450, and 800 W at three treatment times (2, 5, and 8 min). The results indicate that under pretreatment conditions of 1.0 M NaCl and 300 W for 2 min, hemicellulose content decreased by 7.93%, cellulose increased from 32.96% to 39.69% (untreated and pretreated, respectively), and lignin content decreased to 20.56%. The predicted lignin residue from the model was 13.85%, and 2 M of NaCl at 600 W for 8 min were determined to be the optimal conditions. Sample morphology following pretreatment was analyzed using scanning electron microscopy. MAIS was found to be effective and efficient for removing hemicellulose and lignin residue.