摘要：

尿素的高效利用一直是环保型农业的一个非常重要的研究课题。本工作利用两种天然多糖魔芋葡甘聚糖（KGM）与黄原胶（XG）在形成凝胶过程中的协同作用以及简单的包埋工艺，制备了包埋尿素的KGM/XG复合凝胶，并系统地研究了不同组成的复合凝胶在不同温度和pH环境中尿素的释放特性。结果表明，不同组成的包埋尿素的复合干凝胶在中性水介质中的尿素释放行为表现出3个具有不同特征的阶段。在释放的初期，释放速率较快，尿素的累积释放率随时间显著上升；在第二阶段，尿素的释放与包埋达到基本平衡，期间尿素的累积释放率无明显增加；在释放时间达22～24 h后，进入第三阶段，溶胀的复合凝胶出现崩解，释放速率再度加快，并在32～45 h后达到释放平衡。各阶段的持续时间与复合凝胶的载药量、m_KGM/m_XG和介质的温度有关。介质的pH

关键词: 葡甘聚糖, 黄原胶, 复合凝胶, 尿素, 缓释

Abstract:

The effective utilization of urea has been an important research area of environmentally-benign agriculture.In this study the KGM/XG plural gel embedding urea was prepared by the use of the synergism between two kinds of natural polysaccharides, konjac glucomannan (KGM) and xanthan gum (XG) and a simple embedment method.The release performance of urea from the prepared plural gel with different compositions were investigated in aqueous medium under the condition of different pH values and temperatures.The results showed that the release behavior of the dry plural gel embedding urea in neutral water bore the characteristics of three stages.In the initial stage, urea released fast and the accumulative release amount of urea increased with time.In the second stage, the release of urea from the plural gel and the embedding of urea into the plural gel reached basically a balance, and then the accumulative release amount of urea stayed relatively stable. In the third stage after having released for 22—24 h, the swollen plural gel crumbled, leading to quick release of urea, and the new balance came within 32—45 h.The duration of each stage was closely related to the urea-loading amount and the mass ratio of KGM to XG in the plural gel, and also to the temperature of aqueous medium.Besides, the pH of aqueous medium had a strong influence on the release behavior of urea from the plural gel.In the pH>7.0 alkaline medium, the release of urea would be accelerated and the accumulative release amount of urea would increase remarkably.The accumulative release amount of urea was over 90% within 50 h.On the contrary, the acidic medium would repress the release of urea, and the accumulative release amount of urea was only 11.8% at the pH 2.0 aqueous medium within 50 h.Therefore, slow release of urea from the plural gel within a relatively long time could be realized in the acidic medium.

Key words: 葡甘聚糖, 黄原胶, 复合凝胶, 尿素, 缓释