Enhanced adsorption of rhodamine B from water by Fe-N co-modified biochar: Preparation, performance, mechanism and reusability

To adsorb rhodamine B (RhB) in wastewater by pristine biochar was limited, while the modified biochar has shown great potential adsorption performance. Here, coconut shell mixed with FeSO4·7H2O and urea was prepared to synthesize Fe-N co-modified biochar by once pyrolysis method at 500℃. The results showed Fe-N-BC had larger surface area (972.8714 m2·g-1), higher developed porous structure (0.65016 cm3·g-1), and more oxygen-containing groups, which collectively contributed to significantly improve the adsorption performance of the Fe-N-BC towards RhB. The maximum adsorption capacity of RhB reached 12.41 mg·g-1 by Fe-N-BC which was 1.58, 1.43 and 1.26 folds than that of BC, N-BC and Fe-BC, respectively. The mechanism of adsorption for Fe-N-BC towards RhB including ion exchange, pore filling, surface complexation, H-bond and π-π interaction. This study indicates that Fe-N-BC is an excellent adsorbent for RhB removal from wastewater.