Efficient removal of crystal violet using Fe₃O₄-coated biochar: the role of the Fe₃O₄ nanoparticles and modeling study their adsorption behavior

摘要

Biochar shows great promise for use in adsorbing pollutants. However, a process for enhancing its adsorption capacity and re-collection efficiency is yet to be further developed. Hence, in this study, we developed a type of biochar coated with magnetic Fe₃O₄ nanoparticles (i.e., magnetic biochar (MBC)) and assessed its use for crystal violet (CV) adsorption as well as its recycling potential. The coating of Fe₃O₄ nanoparticles, which was not only on the surface, but also in the interior of biochar, performed two functions. Firstly, it produced a saturation magnetization of 61.48?emu/g, which enabled the biochar being efficiently re-collected using a magnet. Secondly, it significantly enhanced the adsorption capacity of the biochar (from 80.36 to 99.19?mg/g). The adsorption capacity of the MBC was determined to be the largest by so far (349.40?mg/g) for an initial CV concentration of 400?mg/L, pH of 6.0, and temperature of 40?°C, and the adsorption capacity of re-collected MBC was 73.31?mg/g. The adsorption of CV by the MBC was found to be a spontaneous and endothermic physical process in which the intraparticle diffusion was the limiting step. These findings inspire us to use other similar materials to tackle the menace of pollutions.