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

Abstract

Fe3O4@C/Ag (Magnetic) nanoparticles (Nps) were synthesized by in situ solvothermal method. The average size of Fe3O4 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 NaBH4, 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 (ΔSθ), standard Gibbs free energy change (ΔGθ), activation energy (Ea) and standard enthalpy change (ΔHθ) 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.