The Preparation And Slow-release Performance Of Urea Fertiliser Coated By Ethyl Cellulose And Konjac Glucomannan

To minimize nitrogen fertilizers losses,an alternative is the creation of a physical barrier around granules.The way to coat granules with polymers is popular.In this paper,the urea was coated with konjac glucan-mannan(KGM),ethyl cellulose(EC)and konjac glucan-mannan chitosan-ethyl cellulose(KGM-EC)composite membrane by the method of drumming-spraying and thermosetting of coating pan.The optimal preparation conditions was discussed by the rate of membrane and caking.Then,to discusse and study basic properties of KGM/EC coated urea;to characterize the structure of coated urea particles and discusses the relationship between the membrane structure and slow-releasing potential.Depending on the results,the KGM coated urea,EC coated urea and KGM-EC coated urea were accorded to certain proportion and mixed together to be a new combination of coated urea,then the desired urea release rate can be achieved or adjusted.The conclusion is as follows:1.The optimum conditions for the preparation of the coating with urea and KGM-EC were determined through orthogonal tests,and the factor's markedness were found by analysis of the experiment result by range analysis and variance analysis.The results showed that,when the KGM:EC was 1:9 in 1% KGM-EC coating(w/v),the coating pan speed was 700 r/min,coating temperature was 60°C,the spraying way was from a physical below inclined upward spray,and the coating liquid is weak acid(pH=6),the coating effect is the best.2.By the test of properties of coated urea granules,such as moisture content,particle size,pH and agglomeration of rates,showed that the performance of coated urea was changed after coating.The grain size was increased,moisture content was droped,pH droped,hardness was increased of the coated urea with the increase of amount of coating.The result of scanning electron microscopy envelope structure showed that with the increase of the amount of coating while the slow release rate of coated urea decreased.When the coating was 10% or more than 10%,the coated urea was encapsulated,surface roughness,film compact package.The result of slow-release rates of coated urea in water showed tha the release rate of KGM-EC and EC coated urea were decreased with the increase of coating.3.Mixed in different proportions of coated urea was getting a series of sustained-release rate,and between EC coated urea and urea KGM-EC envelope.And the released rate of urea can be different by the ratio of combination.