Synthesis Optimization and Characterization of Pesticide Sustained Release Microcapsule Based on TEOS

Abstract:

Natural pyrethrins are encapsulated with silicon dioxide gel prepared via the sol-gel method using tetraethyl orthosilicate as precursor. Taking drug loading rate as the evaluation index， the response surface methodology is used to design the BBD （Box-Behnken design） experiment to determine the optimal preparation conditions as follows： pH is 9.02， the dosage of TEOS（tetraethyl orthosilicate） is 0.96 g， and the reaction temperature is 36.5 ℃. The drug loading efficiency and average particle size of the microcapsules are 38.0 % and 13.5 μm， respectively. The results show that the stability of encapsulated drug is significantly improved below 250 ℃. The drug loading efficiency decreases by only 6.2% after it is stored in the dark at 4 ℃ for four months. The microcapsules demonstrate a good sustained-release property， and can effectively reduce the quality loss of the drug at 100~200 °C. The microcapsules also exhibit a high insecticidal activity against Culex pipiens pallens and Aedes albopictus larvae， and are even slightly more effective against aphids and stick insects than the original drug， endowing them with a great application value.

Key words:natural pesticide;pyrethrin;silicon dioxide;microcapsule;sustained release