Studying On Preparation And Controlled Release Performance Of Porous Materials Load Pesticide Controlled Release Formulations

Pesticides are the guarantee of agricultural production, however, depending on wind-blown, solarization, and rainfall, as much as60%～90%of the applied conventional pesticide is lost and decomposed, which not only increases the cost but also leads to environmental pollution. Therefore, focusing on improvement of existing pesticide varieties forms and formulations, and the development of physical and chemical properties, which is very important. Controlled release formulations of pesticides can remarkably reduce the amount of active agent required for using by maintaining an effective concentration in the target area for longer periods of time, thus achieving efficiency, environmental effects. Great deals of studies have been focused on the searching an appropriate carrier material of active substances for controlled release.This paper choose avermectin(AVE) as a guest species, some common irexpensive porous materials, such as attapulgite(ATP), red brick, fly ash, active carbon, molecular sieve, and nano silica, were used as delivery carriers of AVE. AVE has been successfully adsorpted into the above carriers using an isovolume impregnation method to obtain a series of avermectin controlled release formulations(CRF). The influence of formulation compositions, such as the loading amount of AVE, the physical and chemical properties of carrier materials and the type of carrier materials on the controlled release performance of AVE was investigated. The synthesis strategy of CRF, feasibility of porous materials used as controlled release drug carriers, release behaviour, release mechanism, and the relationship between porous structures and release behavior of CRF were systematically studied in terms of ultraviolet spectrophotometry, XRD, FT-IR, and BET. The result showed that the pore volume and adsorption capacity of ATP strengthen much by acid modification, it was found that acid modificated ATP was a better CRF carrier. The release rate of AVE will decrease with the decrease of the loading amount of AVE. While Red brick particle of20-30mesh number was used as a carrier, AVE’s release rate was slowest in red brick particle of all mesh number. Aiming at controlled release performance, alkali modification was the best modification way of fly ash. However, red brick and fly ash weren’t good CRF carriers, because of their lower porous volume and specific surface area. It was revealed that the controlled release performance of AVE was closely related to the porous structure properties of the carrier materials. The releasing porcess of AVE was quantitatively described by three kinetic models:the Higuchi kinetics model, Rigter-Peppas kinetic model, and Logistic kinetic model. However, the fitting of Rigter-Peppas model and Logistic model were better, Higuchi kinetics model was the worst. The fitting result of Rigter-Peppas indicated that the releasing behaviour of AVE involved physical diffusion, ions exchange and drug dissoulution. The fitting result of Logistic indicated that the releasing behaviour of AVE is complex coupling of crumbling and dissolving.