Sugarcane Bagasse Fibers Derivatives and Their Application in Chitosan-Based Composite Films for NPK Fertilizer Release

Encapsulation and release of NPK fertilizer by composite films were systematically demonstrated by casting dispersions of chitosan (CS) and sugarcane bagasse (SCB) derivatives (holocellulose (HC), cellulignin (CL), and cellulose (CEL)) fibers under varied CS-to-NPK and CS-to-SCB derivatives mass ratios. SCB derivatives were obtained from sugarcane bagasse as agricultural waste by following the alkali dissolution (4% NaOH, 70 °C for 5 min), sodium chlorite delignification (1.4% NaClO2, pH 3.5, 70 °C, 5 h), or from a combination of both. Nutrientadsorption capacity can be tunable by the chemical composition of SCB derivatives, i.e., fibers with noncellulosics exhibited higher adsorption capacities while the absence of noncellulosics lessened their adsorption capacity. Oven-drying (60 °C, 5 h) of optimal 1:0.5 CS/NPK film-forming solution produced highly uniform films with shape with 0.31 ± 0.02 mm thickness while increasing fiber content in the solution to 25 or 50% prevents films retraction effect. The release of highly water-soluble NPK fertilizer from these composite films was lower with hemicelluloses (52-82%) or lignin (55-92%) contents in SCB fiber than in noncellulosics absence (71-100%), thus could be tuned by varying the chemical composition SCB derivative, followed by a quasi-Fickian diffusion mechanism in water.

本研究系统探究了复合膜对氮磷钾（NPK）肥料的包埋与缓释行为：通过流延法制备壳聚糖（chitosan, CS）与甘蔗渣（sugarcane bagasse, SCB）衍生物纤维的分散液，其中调控了CS与NPK的质量比，以及CS与SCB衍生物的质量比。SCB衍生物以农业废弃物甘蔗渣为原料，分别通过碱溶法（4% NaOH，70 ℃下反应5 min）、亚氯酸钠脱木质素法（1.4% NaClO₂，pH 3.5，70 ℃下反应5 h），或结合两种工艺制得，所述SCB衍生物包括综纤维素（holocellulose, HC）、纤维素木质素（cellulignin, CL）与纤维素（cellulose, CEL）三类纤维。养分吸附容量可通过SCB衍生物的化学组成进行调控：含有非纤维素组分的纤维表现出更高的吸附容量，而不含非纤维素组分的纤维吸附能力则显著降低。将最优配比为1:0.5的CS/NPK成膜液置于60 ℃烘箱中干燥5 h，可制备得到厚度为0.31±0.02 mm的均匀平整膜；当分散液中纤维含量提升至25%或50%时，可有效抑制膜的收缩效应。与不含非纤维素组分的复合膜（养分释放率为71%~100%）相比，SCB纤维中含有半纤维素（52%~82%）或木质素（55%~92%）的复合膜，对高水溶性NPK肥料的释放率更低。由此可通过调控SCB衍生物的化学组成，实现NPK肥料释放行为的精准调控，且该复合膜在水中的养分释放机制符合准菲克（quasi-Fickian）扩散行为。