Preparation and Characterization of Chitosan-Coated Diatomaceous Earth for Hexavalent Chromium Removal

A novel chitosan coated diatomaceous earth (CDE) beads were prepared by the drop-wise method and characterized by Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and zeta potential. Prepared CDE beads were used for Cr(VI) adsorption from aqueous systems. The effect of several factors including solution-pH, initial Cr(VI) concentration, temperature, and contact time on adsorption process was examined. The adsorption results revealed that the Cr(VI) adsorption was fitting well the Langmuir model indicating a homogeneous adsorption surface for Cr(VI) on the CDE beads. The kinetics of adsorption suggested a pseudo-second-order model fitting better than the pseudo-first-order model. The maximum Cr(VI) adsorption capacity onto prepared CDE beads was 84.23 mg/g. In competition adsorption, the affinity of CDE beads toward mixed metal ions was high for Cr(VI) followed by Pb(II) and it was low for Zn(II) and Ni(II). Loaded CDE beads with Cr(VI) were successfully regenerated by NaOH and reused up to five cycles. The overall results emphasize that the CDE beads could be used as an economically applicable and sustainable adsorbent for Cr(VI) removal from aqueous solutions.