Intercalation, Assembly, Hybridization Of LDHs And Adsorption Property Of LDHs Hybrid-materials

The structures of layered double hydroxides (LDHs), preparation methods, properties and applications of LDHs were summarized in this chapter. The intercalation of calcein into LDHs had been investigated by the ion-exchange method and its physical and chemical properties were studied. Fe3O4/CLDH composite was prepared and the properties were also investigated. The adsorption of AY2G from aqueous solution by Fe3O4/CLDH was also studied.(1) The intercalation of calcein into Mg/Al-NO3-LDHs and Zn/Al-NO3-LDHs by co-precipitaiton and ion-exchange method has been investigated. The obtained intercalation compounds were characterized by XRD, IR, TG-DSC, UV and EA techniques. The results show that the original interlayer nitrate ions can be replaced by the organic anions under the controlled conditions. From the XRD data, the guest size and the orientation of anions between the layers were determined and after intercalation the interlayer spaces of the materials are expanded to1.81and1.75nm, respectively. FT-IR and DSC/TG curves reveal the presence of a complex system of supramolecular host-guest interaction and the increase of thermal stability of materials. UV adsorption spectroscopy indicate that the confinement of the calcein in their anionic form within the restricted space of the interlayer region of LDHs is in favor of guest-host and guest-guest interactions so that the UV absorption range and ability of the intercalation compounds are changed.(2) Fe3O4is formed by hydrothermal method and Fe3O4/LDHs composite particles were prepared by the co-precipitation method and then followed by calcination at450℃for4h (Fe3O4/CLDH). The obtained materials were characterized by powder X-ray diffraction (XRD), SEM, FT-IR spectroscopy and VSM. The results indicate that pure Fe3O4is formed by hydrothermal method in the reaction and it has complete structure and single crystal phase and the magnetism performance is good. SEM show that the Fe3O4consists of well-dispersed sphere with an average size range300nm. The magnetism performance of Fe3O4/CLDH is still good after calcination。It is suggested that this phenomenon is connected with the surface LDHs, indicating that the Mg/Al layered double hydroxide can protect Fe3O4from oxidation even without N2protection.(3) The adsorptive removal of Acid Yellow2G from aqueous solutions by Fe3O4/CLDH was investigated in batch experiment。 The effects of contact time, initial dyes concentration, competing anions, solution pH value, temperature affected the adsorption were investigated. The results show that Fe3O4/CLDH can be used as an effective adsorbent for the removal of AY2G from aqueous solution. The results of kinetics study showed that data fitted the pseudo-second order model well. The Langmuir model were applicable for describing the sorption isotherms. The thermodynamic parameters(ΔH, ΔS and ΔG) calculated from the temperature dependent adsorption isotherms indicated that the adsorption process of dyes on Fe3O4/CLDH was endothermic and spontaneous. The removal rate of dyes is above85%for Fe3O4/CLDH after5cycles indicating the feasibility of Fe3O4/CLDH regeneration.