2. Experimental section
Materials synthesis: The dispersible Fe3O4 nanoparticles and Fe3O4@C microspheres were synthesized according to the method reported previously [8]. Subsequently, the dried Fe3O4@C materi-als were impregnated in ZnCl2 solution (the mass ratio of ZnCl2/ Fe3O4@C¼4:1) for 6 h, and dried at 110 1C for 12 h and then was activated in a N2 atmosphere at 400 1C for 1 h. After cooling down, the activated samples were thoroughly washed with distilled water and HCl solution (0.5 M). Finally, the materials were dried under vacuum at 80 1C for 10 h to obtain HPCS.
Characterization: The X-ray diffraction (XRD) patterns of pow-der samples were taken by a Bruker D8 Advance diffractometer using Cu Kα radiation (λ¼0.15418 nm) as an X-ray source. N2 adsorption–desorption isotherms were carried out at 196 1C using a micromeritics ASAP 2020 analyzer. The specific surface area (SBET) was evaluated using the Brunauer–Emmett–Teller (BET) method. The pore size distributions were calculated accord-ing to the Density Functional Theory (DFT) method. Fourier transform infrared spectroscopy (FTIR) spectra of a sample in KBr pellet were recorded on a Nicolet Avatar 370 spectrometer. The morphology was observed from a JEOL JEM–2100 transmis-sion electron microscope (TEM) with an accelerating voltage of 200 KV and a scanning electron microscope (SEM, Hitachi S-4800).
Adsorption studies: The adsorption performance of as-prepared materials was evaluated by removing phenol. Typically, 20 mg of adsorbent was immersed into a 50 mL of certain phenol concen-tration under violent stirring at room temperature. The UV–vis spectra (Shimadzu, UV-2450PC) were used to estimate the adsorp-tion process at a certain time interval.