Preparation Of High-surface-area Mg-Al LDHs As Photocatalyst Support And As Additives To PP Composite Fibers

Layered double hydroxides (LDHs) are a group of layered anionic clay, which consisting of layered structures and special physical and chemical properties. In recent years, LDHs have become a hot research and have potential applications in many fields. In addition, their corresponding mixed oxide has been widely used in scientific research and industrial production, especially as adsorbent materials or catalytic materials. LDHs have high anion exchange capacity and can be used as anion exchange materials. The calcined products have high surface area and adsorption capacity, and are suitable as catalyst support. Besides, LDHs has thermal decomposition, excellent infrared absorption capacity and a wide range of infrared absorption. Therefore, LDHs can be added into the polymeric matrix to improve performance of polymer.In this paper, high specific surface area Mg-Al layered double hydroxides (Mg-Al-CO3-LDHs) were prepared by co-precipitation-calcinations-reconstruction method. The powders were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscope, N2 adsorption-desorption isotherm. The adsorption of acid red G (ARG) was used as a model dye to evaluate the adsorption abilities of LDHs derived mixed metal oxides (MMO). It was found that LDHs with the smallest crystallite sizes and highest specific surface area were obtained at a reconstruction temperature of 6℃. LDHs obtained by reconstruction had slit-like mesopores in irregular interconnected flaky sheets, with the specific surface area as high as 217m2/g. And their derived oxides showed excellent adsorption for ARG.High surface area LDHs, made of flaky sheets with slit-like pores, were prepared to support TiO2 and ZnO photocatalysts. The powders were characterized by X-ray diffraction, N2 adsorption-desorption isotherm, field-emission scanning electron microscopy, transmission electron microscope. It was found that the TiO2 nanoparticles were anatase with about 10nm in size. In photocatalytic experiments, the degradation of ARG by TiO2/MMO is efficient, especially the one with the mass ratio of 0.5:1, and degradation ratio is above 90% at 2h. In addition, in the presence of high surface area LDHs as a support, the ZnO nanoparticles were of about 10nm in size and showed higher photocatalytic decomposition of acid red G than bare ZnO powder prepared under similar experimental conditions. It should be noted that the ZnO/MMO combined excellent adsorption with photocatalytic activity. ZnO/MMO with the mass ratio of 0.5:1 can completely remove ARG from aqueous solution within 1h.LDHs and ZnO/LDHs nanoparticles were modified by anionic surfactant sodium dodecyl benzene sulfonate. The modified LDHs and ZnO/LDHs nanoparticles were doped in polypropylene and composite resins were spun by melting spinning. The thermal stability, mechanical properties, far-infrared radiation were measured. It was found that thermal stability, limiting oxygen index (LOI) and far-infrared radiation of composite fibers had been improved.