交联碱木质素--聚乙烯醇基钾镁缓释膜肥对钾、镁的缓释性能

Release performance for K and Mg from alkaline lignin / polyvinyl alcohol cross-linked slow-release film fertilizer

为了提高工业碱木质素的利用率和扩大其应用范围,以工业碱木质素和聚乙烯醇（PVA）为原料、甲醛作为交联剂、添加硫酸钾和硫酸镁制备交联碱木质素-聚乙烯醇基钾镁缓释膜肥。采用FTIR-ATR方法测定缓释膜肥的化学结构,并用淋溶实验检验缓释膜肥对钾、镁的缓释作用。结果表明：1）缓释膜肥在3 260 cm-1左右的峰变小变宽,1 332.57 cm-1处吸收峰消失,1 145.51-983.52 cm-1范围内吸收峰变大,说明碱木质素、聚乙烯醇经甲醛交联有化学反应发生。2）与纯PVA交联薄膜相比,碱木质素的加入不利于钾的缓释,而适量的碱木质素有利于镁的缓释,碱木质素加入量可达20%。随着甲醛加入量的增大,钾累积释放率减小;适量甲醛有利于镁的缓释,但随着甲醛加入量的增大,缓释膜肥对镁的缓释性能降低。对镁的缓释,甲醛的合适加入量为3.59%。缓释膜肥对钾的缓释主要是分子结构的物理阻挡作用,而镁缓释除了物理阻挡作用还有木质素的螯合作用。3）对缓释膜肥的动力学试验数据进行拟合,钾缓释的4种模型拟合程度都很高,其中Higuchi模型拟合程度最高,决定系数为0.994 1,说明钾缓释行为遵循Fick扩散。镁缓释模型中Ritger-Peppas模型的拟合程度最高,决定系数为0.974 2,其缓释指数（0.5≤n≤1.0）表明镁缓释行为是扩散和溶蚀综合作用的结果。

In order to improve the utilization of industrial alkaline lignin and expand its application scope,with alkaline lignin and polyvinyl alcohol（ PVA） as primary materials, formaldehyde as crosslinker,potassium sulfate and magnesium sulfate added,alkaline lignin / PVA cross-linked slow-release film was prepared by casting. The reaction film was characterized by FTIR-ATR. Release performance for K and Mg from alkaline lignin / PVA cross-linked film was measured by leaching experiment. The results showed that：（ 1） the absorption peak was at 3 260 cm- 1,and vanished at 1 332. 57 cm- 1,and became larger between 1 145. 51 - 983. 52 cm- 1,which indicated that the cross-linking reaction occurred between alkaline lignin and PVA with formaldehyde.（ 2） Compared with the cross-linked PVA film,the addition of alkaline lignin was unfavorable for the K release,while the appropriate amount of alkaline lignin was in favor of Mg release. The content of alkaline lignin can be 20%. With the increase of formaldehyde content,the accumulative release rate of K decreased. The appropriate amount of formaldehyde was in favor of Mg release,while the more formaldehyde reduced the Mg release performance of the films. The suitable amount of formaldehyde for Mg slow release was 3. 59%. The mechanism of the slow-release film on K mainly resulted from the physical barrier effect of molecular structure. While for Mg slow-release,inaddition to a physical barrier effect of molecular structure,is was also from the chelation of lignin.（ 3）The kinetic data of the K cumulative release rate was fitted with four fit models. The best-fit model for K release was the Higuchi model and the value of R2 was 0. 994 1,which indicated that the release mechanism of K followed Fick diffusion. However,the best-fit model for Mg release was the RitgerPeppas model and the value of R2 was 0. 974 2. The release index（ n） of Ritger-Peppas model for the Mg cumulative release rate was 0. 5≤n≤1. 0,and the slow-release mechanism of Mg was the synergy of Fick diffusion and dissolution.