Abstract

An efficient composite was constructed based on aminated chitosan (NH2Cs), attapulgite (ATP) clay and magnetic Fe3O4 for adsorptive removal of Cr(VI) ions. The as-fabricated ATP@Fe3O4-NH2Cs composite was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analyzer (TGA), Scanning Electron Microscope (SEM), Zeta potential (ZP), Vibrating Sample Magnetometer (VSM), Brunauer–Emmett–Teller method (BET) and X-ray photoelectron spectroscope (XPS). A significant improve in the adsorption profile was established at pH 2 in the order of ATP@Fe3O4-NH2Cs(1:3) > ATP@Fe3O4-NH2Cs(1:1) > ATP@Fe3O4-NH2Cs(3:1) > Fe3O4-NH2Cs > ATP. The maximum removal (%) of Cr(VI) exceeded 94% within a short equilibrium time of 60 min. The adsorption process obeyed the pseudo 2nd order and followed the Langmuir isotherm model with a maximum monolayer adsorption capacity of 294.12 mg/g. In addition, thermodynamics studies elucidated that the adsorption process was spontaneous, randomness and endothermic process. Interestingly, the developed adsorbent retained respectable adsorption properties with acceptable removal efficiency exceeded 58% after ten sequential cycles of reuse. Besides, the results hypothesize that the adsorption process occurs via electrostatic interactions, reduction of Cr(VI) to Cr(III) and ion-exchanging. These findings substantiate that the ATP@Fe3O4-NH2Cs composite could be effectively applied as a reusable adsorbent for removing of Cr(VI) ions from aqueous solutions.

Highlights

  • An efficient composite was constructed based on aminated chitosan ­(NH2Cs), attapulgite (ATP) clay and magnetic ­Fe3O4 for adsorptive removal of Cr(VI) ions

  • Fourier Transform Infrared Spectroscopy (FTIR) spectrum of ­NH2Cs points out absorption bands at 2901, 2216 and 1619 ­cm−1 which correspond to C­ H2, COH stretching and N–H bending vibrations, r­ espectively[46]

  • Batch adsorption experiments clarified that the best adsorption capacity values were attained at pH 2 and achieved by ATP@Fe3O4-NH2Cs(1:3)

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Summary

Introduction

An efficient composite was constructed based on aminated chitosan ­(NH2Cs), attapulgite (ATP) clay and magnetic ­Fe3O4 for adsorptive removal of Cr(VI) ions. The magnetization loops of both ­Fe3O4 and ATP@Fe3O4-NH2Cs composite reveal a ferromagnetic behavior as the coericivity values were 198.76 and 90.68 G, respectively. It was obvious that the incorporation of ATP clay greatly enhanced the removal efficiency of F­ e3O4-NH2Cs. the increase in the adsorption capacity with increasing the ­Fe3O4-NH2Cs dosage in the adsorption medium is most likely due to increasing the surface positive charges resultant from the extra amine groups of aminated chitosan ­(NH2Cs).

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