Chitosan modification of magnetic biochar produced from Eichhornia crassipes for enhanced sorption of Cr(VI) from aqueous solution

In this research, chitosan modification of magnetic biochar (CMB) was successfully prepared for effective removal of Cr(VI). Moreover, this study highlighted that the conversion of Eichhornia crassipes into biochar was a promising method for improved management of this highly problematic invasive species. The sorption kinetics, isotherms, thermodynamics, the effects of pH, and background electrolyte on the sorption process were investigated. The results indicated that CMB adsorbed more Cr(VI) (120 mg g(-1)) than that of pristine biochar (30 mg g(-1)). The sorption data could be well illustrated by pseudo-second-order and Langmuir models. Furthermore, thermodynamic parameters revealed that the sorption reaction was an endothermic and spontaneous process. The adsorption of Cr(VI) was influenced by solution pH and the maximum sorption capacity was achieved at pH 2. The background electrolyte PO43- and SO42- restricted the Cr(VI) sorption. These results are significant for exploring and optimizing the removal of metal ions by the CMB composite.