Preparation Of Surfactant Inserted Layered Hydroxide Nickel–zinc Salts And Its Application In The Release Of The Pesticide

Layered metal hydroxides can typically be classified into layered double hydroxides(LDH) and layered hydroxide salts(LHS). Both LDH and LHS are modifications of the brucite-like structure. The structure of LHS is not the metal replacement, but the removal of hydroxide ions from the structure and replacement by water molecules or other types of oxoanions, generating materials with anionic exchange capacity. LHS has the similar anion-exchange properties as LDH, and the higher layer charge and layer thickness than LDH. However, the investigation on synthesis, structure and application of hybrid materials based on LHS are much less than that of LDH. First, the preparation of layered hydroxide nickel zinc salts(NZL) is studied. Secondly, the preparation of anionic surfactant and zwitterionic surfactant intercalated into NZL are investigated. Finally, with the help of the interaction between 3-glycidyloxypropyltrimethoxysilane(GPTMS) and imidacloprid(IMI), a new method is developed to make IMI intercalate into interlayer of NZL to prepare NZL-GPTMS-IMI hybrid materials. Furthermore, release behaviors of IMI from NZL-GPTMS-IMI are investigated and analyzed in buffer solutions, and IMI release mechanism is also analyzed based on five kinetic models.1. The preparation and characterization of NZL. NZL has been prepared by co-precipitation method, the effect of Ni/Zn ratio and pH on the preparation has been investigated in detail. The structure and thermal stability are characterized by XRD, FT-IR and TG-DTA. The result show that NZL with pure phase can be obtained at Ni/Zn=0.5-3.0, pH=6.5-9.0. NZL has higher thermal stability compared to layer hydroxides zinc salts.2. The preparation and characterization of surfactant intercalated NZL. Two anionic surfactants of sodium dodecyl sulfate(SDS) and sodium alcohol ether sulphate(AE2S) and three zwitterionic surfactants of dodecyl dimethyl carboxylbetaine(DCB), dodecyl dimethyl sulfobetaine(DSB) and N-dodecyl-?-aminoprpionate(DAP) intercalated into NZL have been synthesized by the co-precipitation method. The structure and thermal stability of intercalated materials are characterized by XRD, FT-IR and TG-DTA. The result show that both anionic surfactants and zwitterionic surfactants are successfully intercalated into NZL.3. The preparation and release properties of the IMI intercalated materials. Taking NZL-SDS as a precursor, NZL-GPTMS-IMI hybrid materiasl are prepared by ion-exchange method with the help of the interaction between hexadecyl trimethyl ammonium bromide(CTAB) and SDS and the interaction between GPTMS and IMI. The effect of Ni/Zn ratio, the volume of GPTMS and the mass of CTAB on the structure and loading amount are investigated. The structure, composition and thermal stability are characterized by XRD, FT-IR and TG-DTA. In addition, the release behaviors of NZL-GPTMS-IMI in different media are studied. IMI release mechanism is also analyzed based on five kinetic models. The results show the loading amount of NZL-GPTMS-IMI hybrid materials is up to 13.0% under the condition of Ni/Zn=2.0, 15 mL GPTMS and 0.7g CTAB. NZL-GPTMS-IMI hybrid materials have sustained release behavior in water. The release behaviors of NZL-GPTMS-IMI are well described with pseudo second-order and parabolic diffusion models.