Lignin extraction from oil palm Ttrunk by microwave-alkali technique

Abstract

The Klason’s lignin content in oil palm tree (Elaeis guineensis) particularly, oil palm trunk (OPT) was intensively investigated in this study. The Microwave-Alkali (Mw-A) pretreatment experiment was designed using Design Expert 7.0 software. The design of experiment (DOE) for this research was established and conducted based on the two-level factorial design with total of eleven runs which included three centre points. All the experimental runs were randomly performed. The independent variables or factors studied were as microwave power, temperature and heating duration and these were coded by high level (+1) and low level (-1) and their corresponding natural variable range were 500-900 watt, 80-100°C and 40-80 min, respectively. The dependent variable or response investigated was the amount of lignin, YL. Prior to Mw-A treatment, the OPT biomass with less than 1.0 mm (mesh size < No.18) were first presoaked in 2.5 mol.L-1 sodium hydroxide solution in the ratio of 1:10 (solid: liquid). The amount of lignin present in the washed and dried filtrate samples was subsequently determined. In this case, the total content of lignin determined for untreated and microwave-alkali treated were 17.87 and 13.87 (g/100g biomass), respectively. The analysis of variance performed indicated that temperature (A) and temperature*time (AB) interaction were statistically significant. For the complete model, the F-value for the model is 20.35 whilst the oefficient of determination, R2 = 0.9862 and adjusted coefficient of determination, RAdj 2 = 0.9377. A reduced model, involving only the significant terms and term supporting the hierarchy, was subsequently developed. This simply show that the lignin content of OPT under Mw-A pretreatment can be modelled and as much as 22.38% reduction of lignin was attained when the microwave experiment was set at 900 watt, 100°C and 80 min, respectively.

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GRAPHICAL ABSTRACT