LIGNIN AND SODIUM LIGNOSULFONATE PRODUCTION FROM THE BLACK LIQUOR GENERATED DURING THE PRODUCTION OF BIOETHANOL FROM RICE STRAW
Keywords:lignosulfonate, lignin, rice straw, sulfomethylation
AbstractAbstract-HCTN7. Rice straw is considered as an abundant resource to recover hemicellulose, cellulose, and lignin. Lignin, considered as waste from the biomass pretreatment process for bioethanol production, has numerous applications in value-added chemical products such as lignosulfonate, vanillin, guaiacol, quinones, cresol, … Lignosulfonate was used in various industrial processes such as concrete admixtures, oil well dispersants, dyestuff, coal water slurry dispersants, agricultural chemicals, and other industrial binders. However, lignosulfonate production from rice straw is less attractive due to the difficulty of lignin recovery. Therefore, the objective of this study is to recover lignin and optimize the sulfomethylation of lignin originated from rice straw by sodium sulfite for the highest reaction efficiency to produce lignosulfonate. The effects of reactive conditions including reaction time, temperature, and sodium sulfite/lignin ratio on the sulfomethylation are investigated by experiments and analyzed by response surface methodology (RSM). The results demonstrate that quadratic second-order modeling is compatible with experimental data (R-squared value of 99.9%) and all three factors have a great impact on reaction efficiency (p < 0.05). The optimal reaction condition predicted from the empirical modeling is the reaction time of 150 minutes, the temperature of 80oC, and the sodium sulfite/lignin ratio of 1:2 g/g. The verified experiment at the optimal condition produces sodium lignosulfonate with a high reaction efficiency of 96.2% and low surface tension of 48 N/m.
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