Effect of pH on the structure and properties of pesticide intercalated into montmorillonite modified by zwitterionic surfactant

Abstract

DCB (OA, DSB, SB)-MMT complexes were prepared by incorporating zwitterionic surfactants dodecyl dimethyl carboxylbetaine (DCB), N,N-dimethyldodecylamine N-oxide (OA), dodecyl dimethyl sulfobetaine (DSB) and 3-sulphonyl hexadecyldimethylamine (SB) into montmorillonite (MMT). The complexes were characterized by XRD, FT-IR, TGA/DTA and SEM, TEM. Results indicated that the interlayer distances of OA (DSB)-MMT depended on surfactant content and pH value, while those of DCB (SB)-MMT were only related to the surfactant content. The different thermal decomposition processes of complexes were closely related with pH values. Then the pesticide (lambda-cyhalothrin (LCT) or beta-cypermethrin (BCT)) - DCB(SB) micelles were incorporated into the galleries of LCT/DCB-MMT and BCT/SB-MMT hybrids. The basal spaces of LCT/DCB-MMT and BCT/SB-MMT were 4.03 and 4.64 nm, which were larger than those of DCB-MMT and SB-MMT, respectively. The pesticide intercalation was further confirmed by FTIR and TGA/DTA. Furthermore, the release behaviors of BCT (LCT) from the hybrids were compared and analyzed. The pesticide hybrids have the slow release property due to the strong interaction between DCB(SB) and MMT. The pseudo second-order and parabolic diffusion models can be well used to fit the release data. The present study is conducive to the application of MMT as good carriers of pesticide delivery system.