Synergistic effects of pyrolysis temperature, iron ion concentration and solid/liquid ratio on the properties and Cr(VI) removal performance of magnetic carbon

Magnetic biochar was successfully prepared from the waste Zanthoxylum branch and applied for Cr (VI) removal from wastewater. Modification parameters including concentration of iron-containing solution, ratio of Fe (III)/Fe (II), and pyrolysis temperatures were systematically investigated. There was a synergistic effect of synthesis conditions on the porous structure and the form distribution of iron. Based on the adsorption experiments, 900MZB8–1 displayed the best Cr (VI) removal performance (42.68 mg/g). The fitting result confirmed that the Cr (VI) removal reaction was the homogeneous chemisorption , and the predicted maximum removal capacity could reach at 215.44 mg/g. Moreover, the XPS analysis indicated that 79 % of Cr (VI) on adsorbent surface was transformed to Cr (III) by the cooperation of oxygen-containing functional groups and reductive iron. Meanwhile, 900MZB8–1 maintained the eminent removal efficiency of 80.65 % after four regeneration cycles. Additionally, the economic feasibility and practical performance indicated the rich-potential adsorbent for Cr (VI) removal.