Preparation and characterization of chitosan/montmorillonite magnetic microspheres and its application for the removal of Cr (VI)

Abstract A magnetically separable adsorbent, named chitosan/montmorillonite–Fe3O4 (CTS/MMT–Fe3O4) microsphere is prepared by microemulsion process and characterized by infrared spectroscopic analysis (IR), X-ray Powder Diffraction (XRD) and scanning electron microscope (SEM). The microspheres are applied as adsorbents for the removal of Cr (VI) from aqueous solution. The effects of MMT content (wt%), the initial concentration of Cr (VI) solution (C0), initial pH value (pH0) of Cr (VI) solution and the adsorption dose on the adsorption capacity of the microspheres are investigated. The adsorption experiments show that the adsorption capacity of CTS/xMMT–Fe3O4 microspheres for Cr (VI) is higher than the mean value of those of CTS and MMT. The optimum pH value for Cr (VI) adsorption is found at pH = 2, and the adsorption capacity increased with the increase in adsorption temperature. The adsorption kinetics is better described by the pseudo-second order equation, and their adsorption isotherms are better fitted to the Langmuir equation. Thermodynamic parameters such as ΔH∘, ΔS∘ and ΔG∘ were calculated to understand the adsorption mechanism for Cr (VI). The adsorption–desorption experiments implied that CTS/MMT–Fe3O4 can be used as promising adsorbents for the removal of Cr (VI) from wastewater.