Preparation and utilization of Keggin-type polyoxometalate intercalated Ni–Fe layered double hydroxides for enhanced adsorptive removal of cationic dye

Abstract

The Ni–Fe layered double hydroxide (LDH) intercalated by Keggin-type polyoxometalate (POM) of SiW12O404− was investigated for the first time. The synthesized Ni–Fe LDH and Ni–Fe POM were characterized by XRD, FT-IR, and N2 adsorption–desorption isotherm to identify the intercalation process as well as their surface morphology. The obtained results indicated that after intercalated by POM, the interlayer distance of the LDH expanded due to the insertion of POM anion and removal of some native NO3− anion in the interlayer space. Moreover, the increment of the BET surface area of the material after intercalation indicated the opening of the interlayer space that beneficial for the adsorption process. The study on the malachite green adsorption onto the synthesized materials showed that POM intercalated LDH has better adsorption capacity than the original LDH, where the adsorption kinetic was better described by pseudo second order model than the pseudo first order model.