Preparation And Characterization Of Urea-chitosan Sustained-release Microspheres

Chitosan is a kind of amorphous translucent material which is nontoxic andharmLess with good biocompatibility, wide range of sources, environmentfriendly and easily biodegradable. In addition, chitosan has good adsorption andmoisture absorption. However, chitosan has poor solubility. It could only bedissolved in some diluted acid, insoluble in water, most organic solvents andalkaline solvent. This greatly limits the application of chitosan. A large amount ofliterature reports, chitosan has been widely applied in biology, medicine, foodand agriculture. As a sustained-release vector of fertilizer, chitosan not only candelay the fertilizer release time and resist bacteria, but also easily biodegradable,no pollution to the environment. At the same time, it is the ideal carrier materialfor the sustainable development of human being has an important role in.In this paper, urea-loaded chitosan microsphere were prepared with chitosan ascarrier, formaldehyde and glutaraldehyde as composite crosslinking agent,Span80as emulsifer and liquid paraffin as oil phase via emLusion chemicalcrosslinking method and formaldehyde pre-crosslinked, glutaraldehydecrosslinking method. The various factors affecting the reaction were explored.The impact of stirring speed and the amount of crosslinking agent onmicrospheres loading and encapsulation efficiency were bigger. Then the bettersynthetic technology condition was ultimately determined. The urea-loadingrelease mircospheres were characterized by Fourier transform infraredspectroscopy, Scanning electron microscopy and the test of crosslinking degree.The research shows that urea-chitosan microspheres dispersed and the regularityis better, average particle size is100μm, microsphere surface containing porestructure; urea successfully encapsulated in chitosan microspheres. To comparethe influence of the pore-forming agent with the influence of differentcrosslinking agent, the experimental results show that adding pore-forming agent changed microspheres structure. To compare the microspheres prepared viaglutaraldehyde as crosslinking agent with the microspheres prepared viacomposite crosslinking agent, the crosslinking degrees of urea-chitosanmicrosphere prepared with composite crosslinking agent is more than90%.Experimental results also show that urea release rate is a constant value in thedifferent pH environment. It means that the release process is been not controlledby diffusion medium pH, but by the structure of chitosan carrier coated material.Urea-chitosan microspheres prepared as a slow release fertilizer can be applied inagriculture.