School of Chemical Engineering , University of Queensland , St. Lucia , QLD 4072 Australia.
School of Agriculture and Food Sciences , University of Queensland , St. Lucia , QLD 4072 , Australia.
J Agric Food Chem. 2019 Mar 6;67(9):2449-2458. doi: 10.1021/acs.jafc.8b05709. Epub 2019 Feb 25.
Dicyandiamide (DCD) has been studied as a stabilizer for nitrogen fertilizers for over 50 years. Its efficacy is limited at elevated temperatures, but this could be addressed by encapsulation to delay exposure. Here, poly(3-hydroxybutyrate- co-3-hydroxyvalerate) (PHBV) was investigated as a biodegradable matrix for the encapsulation of DCD. Cylindrical ∼3 mm × 3 mm pellets were fabricated through extrusion processing with 23 wt % DCD. Release kinetics were monitored in water, sand, and both active and γ-irradiated agricultural clay loam soils. Raman maps showed a wide particle size distribution of DCD crystals and indicated that Hitachi's classic moving front theory did not hold for this formulation. The inhibitor release kinetics were mediated by four distinct mechanisms: (i) initial rapid dissolution of surface DCD, (ii) channeling of water through voids and pores in the PHBV matrix, (iii) gradual diffusion of water and DCD through layers of PHBV, and (iv) biodegradation of the PHBV matrix. After ∼6 months, 45-100% release occurred, depending on the release media. PHBV is shown to be an effective, biodegradable matrix for the long-term slow release of nitrification inhibitors.
双氰胺（DCD）作为氮肥稳定剂的研究已经超过 50 年。其在高温下的效果有限，但通过封装来延迟暴露可以解决这个问题。本文研究了聚（3-羟基丁酸酯-共-3-羟基戊酸酯）（PHBV）作为 DCD 封装的可生物降解基质。通过挤出工艺制备了直径约为 3 毫米×3 毫米的圆柱形颗粒，其中 DCD 的含量为 23 重量%。在水中、沙中和活性及γ辐照农业粘壤土中监测了释放动力学。拉曼图谱显示 DCD 晶体的粒径分布较宽，并表明日立的经典移动前沿理论不适用于该配方。抑制剂的释放动力学由四种不同的机制介导：（i）表面 DCD 的快速初始溶解，（ii）水通过 PHBV 基质中的空隙和孔隙的通道化，（iii）水和 DCD 通过 PHBV 层的逐渐扩散，以及（iv）PHBV 基质的生物降解。大约 6 个月后，根据释放介质的不同，释放了 45-100%的 DCD。PHBV 是一种有效的、可生物降解的基质，可用于硝化抑制剂的长期缓慢释放。
