Surface oxidized nano-cobalt wrapped by nitrogen-doped carbon nanotubes for efficient purification of organic wastewater

Abstract Dyes and antibiotics in the wastewater discharged by factories have caused immeasurable harm to natural water bodies. It is of great significance to remove the organic pollutants from wastewater. Herein, a novel magnetic nanomaterial of surface oxidized nano-cobalt wrapped by nitrogen-doped carbon nanotubes (Co@CoO/NC) was prepared through a one-step annealing method and used as efficient adsorbing material for tetracycline (TC) and rhodamine B (RhB). The maximum adsorption capacity of the optimal Co@CoO/NC for RhB and TC was 679.56 mg·g-1 and 385.60 mg·g-1, respectively. As a kind of magnetic recyclable and reused adsorbent, Co@CoO/NC could respectively maintain 75% and 84% of absorption capacities for TC and RhB after four repetitions. The adsorption processes were well matched with the pseudo-second-order kinetic model and the Langmuir model. The Zeta potential, XPS, FT-IR and theoretical calculation results showed that the hydrogen bonding and π-π electron donor-acceptor interaction dominated the adsorption of TC and RhB. Due to the presence of CoO on the surface of Co nanoparticles, cation exchange and surface complexation also played an essential role in the adsorption of TC. This work provides a new opportunity for the rational design and construction of efficient, stable and easily recyclable adsorbents in environmental remediation.