Preparation, Characterization And Properties Evaluation Of Photodegradation Avermectin Microcapsules

With the development of science and technology,more and more measures can be adopted to control pests,while more and more severe negative effects were brought out.Thereby,now scientists focus on the investigation of the green pesticides and formulation which mostly deals with study of super highly-active,lowly poisonous,lowly residual and noncontaminated chemical pesticide.Thereinto studies on green pesticides with photocatalyticdegradation activity attract increasingly attentions.In this article,the carriers of photodegradation sources have been prepared.The microcapsules were prepared by layer-by-layer polyelectrolytes self-assembly using chitosan,alginate and recrystallizated avermectin as shell materials.The coated colloids were characterizedusing confocal laser scanning microscopy(CLSM) and scanning electron microscopy(SEM).Four factors,including chitosan,alginate,AVM and CaCl₂,and three levels for each factor that may affect the formulation of microencap sules were selected andarranged in an L₉(3₄ ) orthogonal experimental table.The four factors in the Optimization system affected the evaluating indicatordifferently.AVM behaved as the maximum followed alginate and CaCl₂.However,the chitosan,alginate and CaCl₂ did not influence.The orthogonal experiment was checked up and the result indicated thatDL%and EE%were 96. 35%and 98.00%respectively.The invitro controlled release pattern of AVM through the PE diffusion barrier was studied using a diffusion cellassembly at physiological pH of 7.0.carriers of photodegradation sources have been prepared,and weremodified to enhance photocatalytic activity,their surfaces were changed for highly absorption capability topesticides.The research also involved on furmulation of pesticide,and analysed the photodegradation effciency of the different carriers at the ultraviolet radiation and sun's ray.The pertinent investigative works have been carried out as follows:With the characterization of the recrystallizated avermectin and microcapsules,the CLSM micrographs showed that the form of the crystal was regular which was propitious to self-assembly and the avermectin-loaded microcapsules have little aggregation.SEM micrographs showed that the avermectin-loaded microcapsules had a rough surface in contrast to the smooth surface of the technical avermectin.The results of electrophoretic potentials showed that electrical charges on the surface of microcapsules were changed inversely after every deposition of polyelectrolytes.The results obtained from SEM and electrophoretic potentials suggested that chitosan and sodium lignosulphonate can alternately deposit on avermectin to obtain avermectin-loaded microcapsules. The invitro controlled release pattern of AVM show that:The released ratio falled of AVM microcapsules was along with the coat increased.This trend showed that the released of the AVM microcapsules could control the coat number of self-assembly.TiO₂ particles were prepared by direct hydrolysis of Ti(SO₄)₂ at a certain temperature, colloidal sol,addition of crystal seeds and ageing.The particles were of good single dispersedness and thermal stability with about 22 nm diameter and above 80 m²/g ratio surface. TiO₂ depositeded with Ag and W was prepared and characterized using scanning electron microscopy(SEM).The SEM micrographs showed that the structure of the non-modified TiO₂ was much holes.When the TiO₂ was coacervation,Ag and W were appeared on the TiO₂ as well as the form of rice.The photocatalytic degradation of AVM in a suspension with the different carriers as catalyst was carded out by radiation of UV-light and sunlight.Two hours were passed in the UV-light,the different degradation carriers have put up different degradation ratios.The ratio of Ag/TiO₂ was 41.7%,the TiO₂ was 58.3%and the W/TiO₂ was 60.81%。Ten days were passed in the sunlight,the degradation ratio of the three carriers were all 99% upwards.Thereinto,the Ag/TiO₂ was degradated comparatively quick,the TiO₂ was degradated comparatively slow.Comparing to photodegradation the different activity for the formulations,the W/TiO₂ was the best of them.So the W/TiO₂ carrier was chosed as the carrier of photodegradation.Toxicity of the novel 50%W/TiO₂-AVM was higher in the adult stage compared to the 95%AVM as indicated by the lower LC₅₀ value.So at the same concentration,W/TiO₂-AVM was much better virulence than the 95%AVM.