Studies On Synthesis And Controlled Release Of Chlorpyrifos Slow Release Agent Based On Graphene Oxide-Zinc-Aluminum Hydrotalcite Composites

Layered double hydroxide(LDH)is a layered material with positive and interlayer with anions.Graphene oxide(GO)has a large specific surface area,lamellar with a negative charge,with superior adsorption capacity and good biocompatibility,which is an ideal slow release drug carrier.LDH and GO can form a new composite GO-LDH by electrostatic interaction.This kind of material is a good pesticide slow release agent which can be loaded with pesticides,prolong the effect and reduce the environmental pollution.In this paper,the pesticide chlorpyrifos first loaded on GO-LDH to form CPF/GO-LDH composites,the structure and sustained release behavior of the composites were studied;Secondly,the structure and release behavior of amphoteric surfactants or zwitterionic surfactants form a micelle with CPF loaded on GO-LDH composites were investigated;In addition,the preparation and characterization of dodecyldimethylcarboxy betaine(DCB)in GO-LDH intercalation materials were studied.The main results are as follows:1.Preparation and release properties of CPF/GO-LDH Composites.A series of the graphene oxide-ZnAl-layered double hydroxide composites containing pesticide chlorpyrifos(CPF/GO-LDH)were fabricated by an exfoliation-restacking method.CPF/GO-LDH composites were characterized by powder X-ray diffraction(XRD),Fourier Transform Infrared Spectroscopy(FT-IR),Scanning Electron Microscope(SEM),Transmission Electron Microscopy(TEM)and Thermogravimetry Analysis and Differential Scanning Calorimetry(TGA-DSC).The results show: the interlayer distances of CPF/GO-LDH with various GO/LDH mass ratios were in the range of 0.70～0.87 nm;the combustion temperature of CPF in the composites was enhanced 130～170°C;the sustainable slow releases were observed during the whole study stage,and the release rates and equilibrium release amounts of CPF were closely dependent on release mediums and GO/LDH mass ratios.The release behaviors of CPF/GO-LDH were well fitted with pseudo second-order and parabolic diffusion models.2.Preparation and release properties of CPF/GO-DCB(DSB,DAP)-LDH.Take DCB,dodecyl dimethyl sulfobetaine(DSB)and N-dodecyl-β-aminoprpionate(DAP)which were solubilized CPF as micelle,respectively,then the micelle was loaded onto the GO stiring with LDH to form the composite material CPF/GO-DCB(DSB,DAP)-LDH by an exfoliation-restacking method.CPF/GO-DCB(DSB,DAP)-LDH composites were characterized by XRD,FT-IR and TGA-DSC.The slow release experiments were carried out in pH 5.0 and 6.8 buffer solution,and the dynamic release analysis was carried out.The results show: the interlayer distance of CPF/GO-DAP-LDH is 0.77 nm,the interlayer distance of CPF/GO-DSB-LDH is 0.88 nm and the interlayer distance of CPF/GO-DCB-LDH is 1.02 nm,CPF insets into the composite material CPF/GO-DCB-LDH layer successfully;the results show that the release behavior of the composites coincides with the quasi-second-order reaction model and the parabolic diffusion model.3.Preparation and characterization of GO-DCB-LDH intercalation materials.GO-DCB-LDH composites were prepared by co-precipitation method and ion exchange method,respectively.The effects of solvent type,reaction temperature,reaction time and the amount of DCB on the structure were investigated.The structure was characterized by XRD,FT-IR,TGA-DSC and SEM.The results show that DCB can be successfully intercalated in GO-DCB-LDH by ion exchange.