羟甲基交联碱木质素锰肥的锰离子缓释动力学研究

Kinetics of manganese ions release from cross-linked hydroxymethyls alkali lignin manganese fertilizers

为改善中国北方土壤缺锰的问题,该文以麦草碱木质素为原料制备了羟甲基碱木质素(HMAL);以物理混合的方式添加硫酸锰,以甲醛、尿素作为交联剂使HMAL发生缩合交联制备了羟甲基交联碱木质素锰肥(CHMAL-Mn)。CHMAL-Mn肥产率为93.7%,CHMAL-Mn肥的锰离子的饱和负载量为48mg/g;其红外光谱表明甲醛成功交联羟甲基碱木质。以7种常见动力学和概率分布的数学模型对CHMAL-Mn肥的锰离子累积释放率的动力学试验数据的进行拟合,以R2、均方误差(e)、精确因子(Af)和偏差因子(Bf)的算数平均值比较模型拟合有效性。结果表明:对CHMAL-Mn肥的锰离子累积释放率的动力学试验数据拟合性最好的模型是Ritger-Peppa模型,其R2、e、Af和Bf的平均值分别为0.9443、0.0083、0.0223和0.0003。当CHMAL-Mn肥的锰负载量为12mg/g时,拟合模型的缓释指数n<0.45,锰离子缓释行为以Fick扩散为主。当CHMAL-Mn肥的锰负载量大于24mg/g时,拟合模型的缓释指数0.45≤n≤0.89,缓释机理为非Fick扩散与骨架溶蚀协同作用。当CHMAL-Mn肥的锰负载量达到饱和值48mg/g时,拟合模型的缓释指数n为0.811,该模型预测CHMAL-Mn肥对锰离子累积缓释率的极大值为79.28%,预测缓释时间为95.92h;模型拟合准确率为96.57%。该研究为可大幅提高碱木质对肥料锰肥的负载量,为碱木质素的综合利用和促进碱木质素在现代农业可降解缓/控释载体领域的应用提供了参考。

With people’s increasing concern about food safety, slow/controlled release fertilizers have become a hot-point in the research and development of fertilizers because of their increasing efficiency of fertilizers, reducing environmental pollution, and increasing crop yields. Lignin can absorb metal ions via carbonyl oxygen and phenolic oxygen of the ligand, while biodegradation of lignin were a slower course, thus progressing to humus formation and the quality of organic matter were enhanced. In a word, lignin showed excellent properties for low cost, safety, and biocompatibility. It has the potential of a kind of agricultural slow/controlled release fertilizer carrier. Although grafting derivatives of alkali lignin get a modified S nutrient release curve, its cost is high. The problem hinders the application of alkali lignin in the agricultural fields as a slow/controlled release carrier. According to Mn deficiency occurs on alkaline soils in northern of china, hydroxymethyls alkali lignin （HMAL） was synthesized with wheat straw alkali lignin and formaldehyde via reacting for 2 hours at 90℃ . Manganese fertilizers of cross-linked hydroxymethyls alkali lignin （CHMAL-Mn） were prepared from HMAL and an appropriate amount of manganese sulfate by physical mixing. Its yield of CHMAL-Mn was 93.7%, and the release data of manganese ion in the static water indicated that the maximum capacity of CHMAL-Mn to loading manganese was 48 mg/g. Cross-linking of hydroxymethyls alkali lignin was proved by IR. CHMAL can significantly increase the amount of Mn load on alkali lignin. The study, which can promote comprehensive utilizations and applications in the field of biodegradable slow/controlled release carrier, is of great significance. In addition, kinetic data of the Mn 2＋ cumulative release rate were fitted with seven fit models of dynamics and probability distribution. The best-fit model was determined by a comparison of the effectiveness of fit models using the values of R 2 , e, A f and B f . The results show that the best-fit model was the Ritger-Peppas model from kinetic data of the Mn 2＋ cumulative release rate. Those arithmetic means of R 2 , e, A f and B f were 0.9443, 0.0083, 0.0223 and 0.0003 separately. When CHMAL-Mn to loading manganese was 12 mg/g, the release index （n） of its Ritger-Peppas model from kinetic data of the Mn 2＋ cumulative release rate is 0.1774. Because of n0.45, slow/controlled release mechanism of CHMAL-Mn shows as fickian diffusion. When CHMAL-Mn to loading manganese was higher than 24 mg/g, the release index （n） of its Ritger-Peppas model from kinetic data of the Mn 2＋ cumulative release rate is among 0.45≤n≤0.89, slow/controlled release mechanism of CHMAL-Mn shows as following synergy of non fickian diffusion and drodible matrix. Especially, when CHMAL-Mn to loading manganese was 48 mg/g, release index （n） of its Ritger-Peppas model from kinetic data of the Mn 2＋ cumulative release rate is 0.811. At that time the Ritger-Peppas model predicts that the maximum of Mn 2＋ cumulative release rate was 79.28%, effective Mn 2＋ release period of CHMAL-Mn was 95.92 h and the model fitting accuracy rate was 96.57%.