毛竹半纤维素的提取及其羧甲基化改性研究

Extraction and Carboxymethylation of Hemicelluloses from Moso Bamboo

关键词:  毛竹  半纤维素  羧甲基半纤维素  改性

Key Words:moso bamboo  hemicellulose  carboxymethyl hemicellulose  modification

摘要:本研究以毛竹为原料，首先通过碱性过氧化氢法制备半纤维素，再采用超声辅助法对半纤维素进行羧甲基化改性。结果表明，液固比20∶1时半纤维素得率最高，达18.00%。半纤维素羧甲基化改性的最佳工艺条件为：NaOH物质的量浓度1.2 mol/L，氯乙酸物质的量浓度0.6 mol/L，碱化时间及温度分别为40 min、30 ℃，醚化时间及温度分别为150 min、70 ℃。随着羧甲基半纤维素取代度的提高，改性前后的半纤维素最大降解温度由257 ℃提升至300 ℃，说明羧甲基化改性有助于提升半纤维素的热稳定性；Zeta 电位的绝对值由9.98 mV提升至38.00 mV（取代度=0.59），且改性后半纤维素的分散性有了明显提升。

Abstract:In this study， the hemicelluloses were separated from moso bamboo via alkaline hydrogen peroxide method， and then modified by carboxymethylation with ultrasonic assistance. The results showed that the highest hemicelluloses yield of 18.00% was achieved at a liquid to solid ratio of 20∶1. The optimum preparation process was proved as follows： the concentration of NaOH was 1.2 mol/L， the concentration of chloroacetic acid was 0.6 mol/L， the alkalization time and temperature were 40 min and 30 ℃，respectively， the etherification time and temperature were 150 min and 70 ℃， respectively. With the increase of carboxymethyl hemicellulose substitution degree， the maximum degradation temperature of hemicellulose before and after modification increased from 257 ℃ to 300 ℃， indicating that carboxymethyl modification could improve the thermal stability of hemicelluloses. Moreover， the absolute value of Zeta potential increased from 9.98 mV to 38.00 mV （substitution degree=0.59）， and the dispersibility of carboxymethyl hemicelluloses was significantly improved.