Controlled Release Of Pesticide From An Organo-Bentonite Based Formulation

The release of pesticide from the controlled release formulation is the best strategy to reduce the agro-environmental pollution. However, controlled release formlation of pesticide is far away from wide application up to date, due to the high cost. To obtain a controlled release formulation of low cost and of release regulation capability, organobentonite, prepared by employing dodecyl trimethyl ammonium chloride (DTMAC) and hexadecyl trimethyl ammonium chloride (HTMAC) as modifying agents, was used as carrier of phoxim and diazinon. incorporating phoxim and diazinon was blended with kaolite, a common inert filler in agricultural chemical industry, to obtain controlled release granule and the release behavior of phoxim and diazinon was studied in water and in soil. The structure of organobentonite was also Investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) and utilized to reveal the influence of structure of the material on the adsorption and release of phoxim and diazinon. The main conclusions of this work are as follows:1. Organobentonite was found to be of excellent sorption capacity towards phoxim and diazinon, and to greatly reduce the release of phoxim and diazinon in water and in soil. The results suggested the feasibility of regulating the release of phoxim via controlling the structure of organobentonite.2. An enhancement of adsorption and release of phoxim can be achieved by increasing the carbon chain of quaternary ammonium, as a result of higher spacing of bentonite. The effects of quaternary ammonium loading were found to be of a close relationship with the interaction of quaternary ammonium with bentonite. An increase of quaternary ammonium loading via electrostatic interaction increased both the adsorption and reduced the release of phoxim, while via hydrophobic interaction decreased the adsorption of phoxim and showed little effect on its release from bentonite.3. The carbon chain and loading of quaternary ammonium exhibited a complex influence on the sorption and release of diazinon in bentonite. The sorption capacity of organobentonite modified by DTMA towards diazinon first decreased and then increased with increasing loading of DTMA, reaching a mimimun around1.0CEC. Compared to the organobentonite of DTMA loading of1.0CEC, a decrease of surfacant loading increased the release of diazinon from the organobentonite-based granule, while the increase of surfatant loading showed little effect on the release of phoxim. In the case of HTMA as modifier, an increase of surfatant loading resulted in a deducing in the sorption capability towards diazinon on the organobentonite and an increase in the release of diazinon.