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

Magnetic carbon nanospheres (MCNSs) dotting with Fe 3 O 4 nanoparticles were synthesized by a simple solvothermal method. Furtherly, KOH activation and HNO 3 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 HNO 3 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 NH 3 -TPD characterizations, KOH activation introduced a large number of pore structures, which significantly increased the specific surface area of MCNSs; HNO 3 acidification further increased the surface acidity of MCNSs, especially C O 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.