玉米秸秆基纤维素保水缓释肥制备及应用.

Recycling of crop straws has been practiced in every conventional agriculture. The increase in the yield of crop straws annually has given rise to a series of serious environmental problems for leaving them to decay or burning on the field surfaces after the harvest. In order to solve these recycling problems of resource wastes during the utilization of crop straws, an experimental study was conducted on the properties and performance of water-retaining concurrently slow-release straw-based cellulose fertilizers, further to discuss their production cost and applicability to the modern agriculture. In this study, the aqueous solution of nitric acid was used to extract the required cellulose from corn straws. A novel semi-interpenetrating polymer networks (semi-IPNs) superabsorbent resin with slow-release fertilizers (MS-CPPC) were prepared through solution polymerization based on corn straw cellulose polymer and linear polyvinyl alcohol copolymer (PVA-APP). Ammonium polyphosphate (APP) was also introduced to supply the nutrients of nitrogen and phosphorus. The design of orthogonal test has been used to optimize the fabrication parameters of the obtained products, as well as the water absorbency of MS-CPPC and the slow-release performance of nutrients in water and soil. The prepared products were also characterized using scanning electron microscopy, flourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermos-gravimetric analysis. The experimental results indicated that acrylic acid (AA) acrylamide(AAm) were grafted onto the chain of corn straw cellulose, and PVA-APP was also involved by semi-interpenetrating with them in the synthesis process of fertilizers. This finding demonstrated that the formation of semi-interpenetrating networks can greatly improve the stability of raw materials. Orthogonal experiments showed that the MS to the acrylic acid mass ratio of 1:6, the MBA to MS mass ratio of 20:1, the initiator to MS mass ratio of 5:1, the PVA-APP to MS mass ratio of 5:2.The fertilizer based on the semi-IPNs superabsorbent resin (SAR) showed excellent water absorbency with the water absorption of 443.2 g/g, while significantly reduced the leaching losses of fertilizers in comparison to traditional fertilizers. Therefore, the application of this products would provide an effective way to solve the leaching loss of fertilizers that often occurred in agricultural fields. The results from the infiltration test showed that MS-CPPC that applied in soil could enhance water absorbency during the infiltration, and effectively inhibit the formation of the soil crust during the rainfall due to the increase in the infiltration rate of soil water. The accumulated release rates of nitrogen and phosphorus in distilled water for one day and 30 days were 14.69%, 13.01% and 67.11%, 55.74%, respectively, indicating the sustained release of nutrients. The release behavior of MS-CPPC was also in good agreement with the National standard on sustained-release fertilizers (GB/T 23348-2009), confirming excellent property of slow release in soil. The slow release behavior of the products can attributed that to a porous structure of the semi-interpenetrating polymer networks, which can restrict the diffusion rate of water molecules into the hydrogel network to delayed dissolution of the encapsulated fertilizer. In the Korsmeyer-Peppas model, the release patterns of nitrogen and phosphorus in the MS-CPPC both follow Fick diffusion and polymer chain relaxation according to the n value. The superabsorbent resin with straw-based cellulose fertilizers become therefore expected to share the combined properties of water-retaining and slow-release, further to provide reducing the production costing while promoting comprehensive utilization of crop straws. [ABSTRACT FROM AUTHOR]