Optimization of microwave pre-treatment conditions for maximum lignin recovery from rice husk using central composite design (CCD) by response surface methodology (RSM)

Response surface methodology based on the central composite design (CCD) was applied to investigate the optimum conditions for lignin recovery from rice husk using microwave pre-treatment. Three operating variables namely microwave irradiation time (min), solid loading (%) and microwave power (Watt), with a total of 20 experiment conditions were conducted to optimize the interaction effects of these variables. The results reported that the second-order model was sufficient for all the independent variables on the response with R2 = 0.9861. Response Surface Methodology predicted a maximum lignin recovery of 34.9076% at optimum conditions for microwave irradiation time, solid loading and microwave power were 16.57 min, 9.66%, and 664 Watt respectively. An experiment was run at the optimal condition and lignin recovery of 33.1667% was obtained. The predicted result was thus experimentally verified. The obtained lignin was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Hydrogen Nuclear Magnetic Resonance (1H NMR) and Carbon Nuclear Magnetic Resonance (13C NMR). The lignin produced from microwave pretreatment showed the presence of varieties of functional groups and potentially used for future applications