Enhanced adsorption of anionic diazo dye by magnetic layered double hydroxide (Zn۰.۵Cu۰.۵Fe۲O۴@SiO۲@Ni-CrLDH) from aqueous solution

A novel magnetic layered double hydroxide known as Zn۰.۵Cu۰.۵ Fe۲O۴@SiO۲@Ni−Cr layered double hydroxide was synthesized with Zn۰.۵ Cu۰.۵Fe۲O۴, SiO۲ and Ni−CrLDH by using coprecipitation method. In order to compare the adsorption efficiency, the Ni−CrLDH sample also was synthesized. The synthesized samples were characterized by X−ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The adsorption of Congo red (CR) by magnetic layered double hydroxide depended upon the contact time, initial dye concentration and pH. The adsorption of the Congo red (CR) reached equilibrium at ۱۸۰ min and followed the pseudo−second−order kinetic equation. The adsorption capacity of the magnetic layered double hydroxide changed significantly between pH ۴−۱۰ and the maximum dye removal were ۸۸% for CR. Moreover, the magnetic layered double hydroxide can be quickly separated from the aqueous solution by an external magnet before and after adsorption process. This indicated that the Zn۰.۵Cu۰.۵Fe۲O۴@SiO۲@Ni−CrLDH composite was an effective adsorbent for CR dye removal with quick separation. The adsorption performance of the synthesized Zn۰.۵ Cu۰.۵Fe۲O۴, SiO۲ and Ni−CrLDH and comparing with Ni−CrLDH show that the Zn۰.۵Cu۰.۵Fe۲O۴@SiO۲@Ni−CrLDH can be more efficient than Ni−CrLDH for removal of CR dye.

Keywords:

Layered double hydroxide , Magnetic separation , Adsorption kinetics , Anionic diazo dye