ZnAl-layer double hydroxides as photocatalysts for oxidation of phenol in aqueous solution

ZnAl-layer double hydroxides (ZnAl-LDHs) with various Zn/Al ratios from 1:1 to 4:1 were prepared by the sol–gel method. The amount of ZnO in the layer double hydroxide was increased by the addition of more Zn hydroxide sol and Zn-oxide-hydroxide/2:1 ZnAl-LDH composites were prepared by heterocoagulation. The samples were calcinated at different temperatures (80–700 °C) and it was shown by XRD and TG measurements that the crystallinity of the samples improves as temperature is increased. The photocatalytic properties of the heat-treated samples were studied in a batch reactor with aqueous phenol solution as substrate. The samples prepared from ZnAl-LDH were shown to have higher photocatalytic efficiencies at 3:1 and 4:1 Zn/Al ratios in the case of mixed phase double hydroxide and ZnO crystals.