Synthesis of floatable magnetic iron/biochar beads for the removal of chromium from aqueous solutions

Blooms of Enteromorpha prolifera (E. prolifera) have caused environmental and economic issues. In this study, E. prolifera was used to synthesize biochar and then prepare effective floatable magnetic iron/biochar (FMIB) beads for the removal of chromium ions from liquids. The optimum iron/biochar mass ratio was 2:1 for chromium ion adsorption. The influence of the test solution pH, bead dose, initial chromium concentration and reaction time between beads and chromium in solution on the removal process was investigated. Characterizations of FMIB beads before and after adsorption were performed to explore the removal mechanism. The removal of Cr(III) is mainly related to adsorption, while the removal of Cr(VI) is controlled by both reduction and adsorption. The results of the kinetic study showed that the chromium ion removal process could be expressed by a pseudo-second-order model. The isotherm experimental data were better fitted by the Langmuir model. Regeneration experiments indicated that the FMIB beads could still remove 21.5 % and 40.5 % of Cr(VI) and Cr(III), respectively, after three cycles. The FMIB beads could remove 87.7% of the total Cr from leather processing wastewater. The beads can float on the water surface and can be quickly collected and separated using an external magnetic field. (c) 2020 Elsevier B.V. All rights reserved.