Magnetic carbon nanospheres: Synthesis, characterization, and adsorbability towards quinoline from coking wastewater

Magnetic carbon nanospheres (MCNSs) dotting with Fe3O4 nanoparticles were synthesized by a simple solvothermal method. Furtherly, KOH activation and HNO3 acidification of MCNSs were carried out to tune surface structure and property of MCNSs for the sake of adsorption improvement. The results show that both MCNSs and modified MCNSs (MCNSs-KH) have magnetic properties, and can be used as adsorbents for rapid separation and reutilization towards quinoline in coking wastewater. After KOH activation and HNO3 acidification, the saturated adsorption capacity of MCNSs-KH is improved to 297.21 mg g−1, much better than that of MCNSs (99.43 mg g−1). According to BET and NH3-TPD characterizations, KOH activation introduced a large number of pore structures, which significantly increased the specific surface area of MCNSs; HNO3 acidification further increased the surface acidity of MCNSs, especially CO functional group, which promoted the acid-base interaction with weakly basic quinoline. From the results of adsorption kinetics, isotherm and thermodynamics, the spontaneous and exothermic adsorption process conformed to pseudo-second-order and Langmuir-Freundlich models better.