Intercalation, characterization and release behavior of imidacloprid into layered hydroxide salts by coupling of (3-glycidyloxypropyl) trimethoxysilane

Abstract

The poorly water-soluble pesticide imidacloprid (IMP) was intercalated into NiZn-layered hydroxide salts (NZL) by the aid of (3-glycidyloxypropyl) trimethoxysilane (GPS). The resulting NZL-GPS-IMP composites were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), carbon solid state nuclear magnetic resonance (13C NMR), thermo gravimetric analysis and differential thermal analysis (TGA/DTA). The interlayer distance of NZL-GPS-IMP was 1.62 nm, which is different from those of NZL-SDS, NZL-GPS and NZL-IMP. XRD and 13C-NMR results showed that SDS anions leave the galleries, and adsorb on the surface. The incorporation mechanism of NZL-GPS-IMP was reasonably put forward. TGA/DTA data showed that the combustion temperatures of IMP and GPS in the gallery were enhanced by 40 and 170 °C, respectively. These indicated that GPS-IMP was intercalated into the gallery. The IMP release behaviors of NZL-GPS-IMP in the water and buffer solutions (pH 5.0 and 6.8) were studied and compared. The IMP release rate and equilibrium release amount were dependent on release environments. Moreover, the release behavior of NZL-GPS-IMP was well fitted with pseudo second-order and parabolic diffusion models. This work would be helpful to develop a potential controlled-release formulation.