Removing anionic dyes from wastewater based on in-situ formation of Fe3O4@Zn-Al layered double hydroxides by self-assembly

A new approach to remove anionic dyes from wastewater was developed by forming Fe 3 O 4 @Zn-Al layered double hydroxides (ZnAl-LDH) in self-assembly process and naphthol green B (NG) with three negative charges was selected as target contaminant. In this process, the successful synthesis of compound and removal of contaminant were accomplished simultaneously. NG in wastewater can be totally removed and the removal efficiency reached the theoretical maximum of LDH removal capacity. The charge-limited removal process and the molecular arrangement of NG molecules in the ZnAl-LDH interlayer were analyzed experimentally and through simulation. The Fe 3 O 4 with small size was complete cover the layers of ZnAl-LDH making it easily separate from wastewater.