Constructing N,S co-doped network biochar confined CoFe2O4 magnetic nanoparticles adsorbent: Insights into the synergistic and competitive adsorption of Pb2+ and ciprofloxacin

To solve the problem of biochar lack of adsorption sites for heavy metal ions and the difficulty of recycling, CoFe2O4 magnetic nanoparticles confined in nitrogen, sulfur co-doped 3D network biochar matrix (C–CoFe2O4/N,S-BC) was designed and fabricated successfully. The obtained C–CoFe2O4/N,S-BC displays remarkable adsorption performance for both Pb2+ and ciprofloxacin (CIP) removal at the single or binary system due to the role of N,S as metal ion anchoring compared to the N,S-free sample (CoFe2O4/BC). N,S co-doped BC not only participates in adsorption reaction but also effectively inhibites the agglomeration of CoFe2O4 nanoparticles and increases the active sites as a carrier at the same time. In the single system, CoFe2O4/N,S-BC demonstrates a fast adsorption rate (equilibrium time: 30 min) and high adsorption capacity (224.77 mg g−1 for Pb2+, 400.11 mg g−1 for CIP) towards Pb2+ and CIP. The adsorption process is befitted pseudo-second-order model, and the equilibrium data are in great pertinence with Langmuir model. In the binary system, the maximum adsorption capacity of CoFe2O4/N,S-BC for Pb2+ and CIP is 244.80 mg g−1 (CIP: 10.00 mg L−1) and 418.42 mg g−1 (Pb2+: 10.00 mg L−1), respectively. The adsorption mechanism is discussed based on the experimental results. Moreover, C–CoFe2O4/N,S-BC shows good practical water treatment capacity, anti-interference ability and stable reusability (the removal efficiency>80% after eight cycles). The rapid, multifunctional, reusable, and easily separable adsorption properties make C–CoFe2O4/N,S-BC promising for efficient environmental remediation. This study also offers a viable method for the construction of adsorption material for complex wastewater treatment.