Preparation and Release Characteristics of Biodegradable Microcapsules Encapsulating Activated Carbon Impregnated with Pesticide Using the Solvent Evaporation Method

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Biodegradable microcapsules entrapping activated carbon impregnated with fenitrotion (MEP), which is used as a pesticide, were prepared by means of the solvent evaporation method in a (solid/oil/water) complex emulsion system. Biodegradable poly-ε-caprolactone (PCL) was used as a wall material. Effects of the preparation conditions, such as the concentrations of PCL and MEP and the weight fraction of activated carbon on the capsule morphology, entrapment efficiency, and release profile of MEP, were investigated. Microcapsules were successfully prepared at relatively large quantities of PCL and activated carbon for MEP. The average diameter of the microcapsules increased with an increase in the concentrations of PCL and MEP and the weight fraction of activated carbon in the organic phase. The entrapment fraction of MEP into the microcapsules was over almost 90% at all preparation conditions and high content of MEP in the microcapsules was achieved. MEP encapsulated in the microcapsules was released to water until the MEP concentration in water reached its saturation concentration. The release rate of MEP decreased with an increase in the PCL concentration and the weight fraction of the activated carbon. Thus, the release profile of MEP could be controlled by adjusting the preparation conditions of the microcapsules.
2004-02-01