RETRACTED: Enhanced Cr(VI) Removal by Nanozerovalent Iron-Immobilized Alginate Beads in the Presence of a Biofilm in a Continuous-Flow Reactor

Abstract

Cr(VI) removal was investigated in a fixed-bed column using nanozerovalent iron-immobilized calcium alginate beads (nZVI–C–A beads) and a biofilm formed on nZVI–C–A beads. The removal studies were performed at various initial Cr(VI) concentrations, different flow rates, and bed heights. Under optimal conditions, nZVI–C–A beads showed 91.35 ± 1.57% Cr(VI) removal and 320.66 ± 3.87 mg/g removal capacity. For biofilm-coated nZVI–C–A beads, the removal percentage and removal capacity were found to be 97.84 ± 0.56% and 473.9 ± 4.84 mg/g, respectively. Breakthrough data were successfully described by the Thomas and Yoon–Nelson model for removal of Cr(VI) using nZVI–C–A and a biofilm on nZVI–C–A beads. Cr(VI) sorption on nZVI–C–A beads and biofilm-coated nZVI–C–A beads were confirmed by X-ray diffraction, energy-dispersive analysis of X-rays, and Fourier transform infrared.