Role of magnetic substances in adsorption removal of ciprofloxacin by gamma ferric oxide and ferrites co-modified carbon nanotubes

Antibiotics have been considered an evolving environmental challenge in the last few decades due to their mutagenic and persistent effects. Herein, we synthesized γ-Fe 2 O 3 and ferrites nanocomposites co-modified carbon nanotubes (γ-Fe 2 O 3 /MFe 2 O 4 /CNTs, M: Co, Cu, and Mn) with high crystallinity, thermostability, and magnetization for the adsorption removal of ciprofloxacin. The experimental equilibrium adsorption capacities of ciprofloxacin on γ-Fe 2 O 3 /MFe 2 O 4 /CNTs were 44.54 (Co), 41.13 (Cu), and 41.53 (Mn) mg/g, respectively. The adsorption behaviors followed the Langmuir isotherm and pseudo-first-order models. Density functional theory calculations revealed that the active sites preferentially appeared on the oxygen of the carboxyl group in ciprofloxacin, and the calculated adsorption energies of ciprofloxacin on CNTs, γ-Fe 2 O 3 , CoFe 2 O 4 , CuFe 2 O 4 , and MnFe 2 O 4 were –4.82, –1.08, –2.49, –0.60, and 5.69 eV, respectively. The addition of γ-Fe 2 O 3 changed the adsorption mechanism of ciprofloxacin on MFe 2 O 4 /CNTs and γ-Fe 2 O 3 /MFe 2 O 4 /CNTs. CNTs and CoFe 2 O 4 controlled the cobalt system of γ-Fe 2 O 3 /CoFe 2 O 4 /CNTs, while CNTs and γ-Fe 2 O 3 ruled the adsorption interaction and capacity of copper and manganese systems. This work reveals the role of magnetic substances, which is beneficial to the preparation and environmental application of similar adsorbents.