Xiaojie Song

Adsorption and intercalation of organic pollutants and heavy metal ions into MgAl-LDHs nanosheets with high capacity

Hexagonal MgAl layered double hydroxide (MgAl-LDH) materials comprised of nanosheets and microsheets with different precipitants were synthesized via a facile hydrothermal route. XRD, FESEM, TEM and BET were employed to characterize the samples. Structural characterization revealed that MgAl-LDHs nanosheets and microsheets are 100 nm and 2 μm in width, respectively. Furthermore, MgAl-LDHs nanosheets have a higher specific surface area (65.94 m2 g−1) than that of microsheets (15.75 m2 g−1). Methyl orange and Cr(VI) anion and Ni(II) cation adsorption on the as-synthesized MgAl-LDHs nanosheets and microsheets were systematically assessed by measuring the residual concentration during the adsorption process. The MgAl-LDHs nanosheets showed better adsorption performance than the MgAl-LDHs microsheets for methyl orange and Cr(VI) anions and Ni(II) cations. The adsorption performance versus time for the adsorption of methyl orange by MgAl-LDHs nanosheets has an excellent adsorption quantity (229.82 mg L−1) with high adsorption rate. The adsorption kinetics and adsorption isotherms of Cr(VI) anions and Ni(II) cations of MgAl-LDHs nanosheets can be described by the pseudo-second order kinetic and Langmuir isotherm with saturated adsorption of 63.8 and 92.3 mg g−1, respectively. Combined with results from XRD, FTIR, EDS and XPS experiments, the adsorption mechanisms of MgAl-LDHs nanosheets including precipitation, surface complexation, isomorphic substitution and ion exchange in the interlayer space of MgAl-LDHs nanosheets are discussed in detail. Finally, based on the quick and efficient removal of heavy metal ions by MgAl-LDHs nanosheets, a filtering-type water purification device was constructed.

Highly efficient photocatalytic activity of Ag3PO4/Ag/ZnS(en)0.5 photocatalysts through Z-scheme photocatalytic mechanism

A novel Z-scheme Ag3PO4/Ag/ZnS(en)0.5 composite material was successfully prepared via a facile hydrothermal method and in situ precipitation. The composites exhibit significantly improved visible light photostability and photocatalytic activity towards methylene blue (MB) and phenol degradation. The excellent performance is mainly ascribed to the Z-scheme system formation of a Ag3PO4, Ag, and ZnS(en)0.5 hybrid. This system does not only enhance the photogenerated electron–hole pairs separation and transfer efficiency, but also maintains strong oxidation and reduction as well. This study may provide new insights to understand and design Z-scheme photocatalysts with high photoactivity.