Research On The Application Of Cellulose-based Hydrogel Materials In Slow-release Fertilizer

Cellulose has many excellent properties such as non-toxicity,biodegradability and wide range of sources,and is widely used in biological,food and pharmaceutical fields.Because the structure of cellulose-based materials containing a large number of hydroxyl groups is suitable for the preparation of environmentally friendly hydrogel materials,cellulose has also been gradually applied to the preparation of hydrogel-type slow-release fertilizers in recent years.However,in the face of cellulose-based natural materials that are widely available in nature with different structures and sources,systematic studies are needed to explore the effects of differences in cellulose structure on the performance of cellulose-based slow-release fertilizers.Therefore,in this study,several common cellulose with different structures(hydroxypropyl cellulose,carboxymethyl cellulose,starch,konjac flour)were selected to prepare a series of water retaining hydrogel slow release fertilizers(Cellulose-g-AA/Urea)with acrylic acid(AA),urea and cross-linking agents,and the effects of the differences in cellulose structures on the performance of hydrogel-like materials were investigated.At the same time,cellulose with better performance was screened as a substrate to prepare wrapped slow-release fertilizer,and the effects and laws of different modification methods on material performance were investigated through experiments of slow release,degradation and plant cultivation,etc.The main contents and results of this study are as follows.(1)The experimental results revealed that the different structures of the groups in the cellulose molecules affect their performance in reaction with acrylic acid and others,which leads to differences in the swelling rate,water retention and fertilizer slow release cycle of hydrogel slow release fertilizers.Hydrogel slow-release fertilizer prepared from starch with better reactivity between acrylic acid and cellulose,produced the highest hydrogel swelling rate,exhibiting the best water retention(35%)within 21 days and the best planting of canola within 60 days.The use of konjac powder(KGM)prepared hydrogel fertilizer,easy to form a tighter cross-link,resulting in such hydrogel swelling is low,but its anti-salt precipitation effect in natural water bodies is better,while wrapped in the hydrogel material within the urea is not easy to dissolve due to swelling penetration,effectively extending the slow-release cycle of the fertilizer,so the slow-release fertilizer in the rape planting experiments also showed a better planting effect.(2)Using starch as the substrate,the envelope material was prepared by copolymerization with polyacrylic acid.In order to improve the processing performance of the material and make the material meet the needs of the wrapping process,urea is added to the material by partial grafting and partial mixing as a modifier,which increases the ductility of the coating material by breaking the high crystallinity of the polymer itself,making the coating material more uniform.In order to guarantee the degradation of slow release fertilizer and slow release fertilizer performance,physical cross-linking is used instead of chemical cross-linking,not only to obtain a more compact film material and improve the slow release effect,but also to achieve a weight loss rate of 71.11% in soil for 60 days,which shows that the degradation performance of the physical cross-linked film material has less impact and makes it possible to achieve significant degradation of polyacrylic acid in soil in a short period of time.This indicates that the degradation of the physical cross-linked envelope material is less influential and allows for significant degradation of polyacrylic acid in soil in the short term.