Synthesis of silver doped Fe3O4/C nanoparticles and its catalytic activities for the degradation and reduction of methylene blue and 4-nitrophenol

The Fe3O4@C/Ag nanocomposite has been successfully synthesized and developed as a highly efficient heterogeneous catalyst for the removal of methylene blue (MB) and reduction of 4-nitrophenol (4-NP) as a representative model of organic pollutants in water. Thermodynamic, kinetic studies of catalytic reactions and catalytic mechanism were also investigated in detail. The as-prepared magnetic materials exhibit significantly improved catalytic performances with excellent cycling stability, and are easily recoverable by an external magnetic field. • Hydrothermal synthesis of Ag doped Fe 3 O 4 @C NPs was reported for catalytic activity. • pH and temperature effect on degradation of MB and reduction of 4-NP were analyzed. • Postcharacterization study verified the recycling ability of the catalyst. F e 3 O 4 @ C / A g (Magnetic) nanoparticles (Nps) were synthesized by in situ solvothermal method. The average size of F e 3 O 4 Nps was 539 ± 4 nm with a 32 nm thick carbon shell layer. Silver Nps was doped on the surface of the carbon shell and used for the catalytic degradation and reduction of methylene blue (MB) and 4-Nitrophenol (4-NP) in the presence of visible light and NaBH 4 , respectively. The as-prepared nanocatalyst was characterized by Fourier transform infrared (FTIR), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), dynamic light scattering analysis (DLS), Energy dispersive X-rays analysis (EDX), UV–visible diffuse reflectance spectra (UV–vis DRS), BET and vibrating sample magnetometer (VSM). Adsorption studies were performed by varying temperature, pH, contact time, initial concentration, and adsorbent dosage in an aqueous solution. Freundlich and Langmuir isotherms models were used for equilibrium data analysis. The kinetic data were fitted with a pseudo-second-order non-linear model. The values of thermodynamics parameters such as standard entropy change (ΔS θ ), standard Gibbs free energy change (ΔG θ ), activation energy (E a ) and standard enthalpy change (ΔH θ ) for both MB and 4-NP were calculated. The values show that the adsorption was spontaneous, endothermic, and followed the physisorption adsorption process. The catalyst can be easily separated from the reaction medium and can be reused for several cycles.