Porous N-doped carbon nanospheres with encapsulated cobalt nanocrystals for persulfate activation to degrade tetracycline

Metal-based nitrogen-doped carbon (M-N-C) materials have attracted wide attention owing to their effectiveness in activating persulfate (PS) for remediation of organic pollutants. Herein, we report a simple method of pyrolysis and simultaneous self-reduction for preparing porous N-doped carbon nanospheres encapsulated with cobalt nanocrystals (Co/p-CN) as a composite catalyst for PS activation. Co/p-CN composite was characterized by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The composite exhibits a high surface area and rich mesoporous structure, which is conducive to exposing more active sites and facilitating mass transport of the matrix. N-doped carbon nanospheres were used to protect the cobalt nanocrystals and N doping helped to fix the Co metal through coordination for manipulating its catalytic activity. After systematic study on the preparation conditions of Co/p-CN composite, it was found that the best Co/p-CN-900 (pyrolyzed at 900 degrees C) could efficiently degrade tetracycline (TC) in 40 min. The quenching experiments showed that Co species in porous N-doped carbon nanospheres caused the oxidation through radicals and nonradicals (SO4 center dot-, center dot OH, O-2(center dot-) and O-1(2)) in the presence of PS. PS activation of Co/p-CN-900 composite involved the mediated electron-transfer for disintegration of refractory organic TC.

Automated summary

In this study, we report a composite catalyst composed of porous N-doped carbon nanospheres encapsulating cobalt nanocrystals, which can activate persulfate (PS) to degrade organic pollutants effectively. The N-doped carbon nanospheres protect the cobalt nanocrystals and N doping helps to fix the Co metal. The composite exhibits a high surface area and rich mesoporous structure, exposing more active sites and facilitating mass transport. The best catalyst composition can efficiently degrade tetracycline in 40 minutes through PS activation involving mediated electron-transfer.