Liquid-Waste Derived Magnetic Porous Carbon Sphere for Effective Removal of Tetracycline from Aqueous Solution

Abstract

To effectively remove tetracycline (TC) from wastewater and to reuse stainless steel pickling wastewater, a novel N-doped magnetic porous graphitic carbon sphere (N-MPGCS) adsorbent was fabricated by a green strategy using tannic acid (TA) as ligand, stainless steel pickling wastewater as metal source, and melamine as nitrogen source. Based on the strong complexing ability between TA and Fe3+/Cr3+ in wastewater, hydrochar spheres can be successfully developed through hydrothermal process. The following simultaneous activation−graphitization endows carbon spheres with abundant pores structure, appropriate O/N functional groups, suitable sp2 carbon, and good magnetic responsivity. Benefiting from these virtues, the optimal adsorbent N-MPGCS1-800 exhibits a high Langmuir adsorption capacity (1005.5 mg g-1 at 45 °C) for TC, fast adsorption kinetics, and good applicability towards pH and co-existing ions. Besides, the excellent magnetism permits the convenient and rapid recovery of adsorbent from the adsorption system. Adsorption studies and characterizations show that H-bond, π-π stacking, and metal-organic complexation interactions contribute to the adsorption together. This work proves that N-MPGCS material can serve as a potential adsorbent for TC, and more importantly, it gives a new path for mining industrial waste to produce high-effective magnetic carbon materials.

Keywords: pickling wastewater, magnetic carbon, green synthesis, adsorption, Tetracycline