Adsorption of Cr(<scp>vi</scp>) onto a magnetic CoFe2O4/MgAl-LDH composite and mechanism study

Magnetic materials as adsorbents can provide effective removal and quickly separate pollutants in wastewater treatment. A magnetic CoFe2O4/MgAl-LDH composite was successfully synthesized through a low saturation coprecipitation method. The adsorption behaviors of Cr(VI) from an aqueous solution by CoFe2O4/MgAl-LDH were investigated. The adsorbents were characterized using scanning electron microscopy (SEM), N2 adsorption–desorption isotherms, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Kinetic and equilibrium studies indicated that the experimental data of Cr(VI) adsorption were best described by pseudo-second-order kinetic and Langmuir models. The maximum adsorption capacity of CoFe2O4/MgAl-LDH for Cr(VI) was found to be 72.4 mg g−1 at an equilibrium time of 300 min and temperature of 283 K. Evaluation of the thermodynamics parameters (ΔH < 0, ΔS < 0 and ΔG < 0) revealed the adsorption process was exothermic and spontaneous. The mechanism study showed that the adsorption of Cr(VI) onto CoFe2O4/MgAl-LDH likely involved adsorption/surface complexation and an ion exchange interaction. This study demonstrated that the magnetic CoFe2O4/MgAl-LDH composite was an effective adsorbent for Cr(VI) removal with quick separation.