Performance of removal of salicylic acid residues from aqueous solution based on the magnetic TiO2 nanocomposites

Magnetic TiO2 nanocomposites with good monodispersity were successfully synthesized via a mild sol–gel method, which were used for removal of salicylic acid (SA) residues from aqueous solution. These as-prepared nanocomposites were extensively characterized by transmission electron microscopy, scanning electron microscope, N2 adsorption–desorption isotherm with the Brunauer-Emmett-Teller method, Fourier-transformed infrared spectra, X-ray diffraction, and vibrating sample magnetometer. These results indicated that magnetic TiO2 nanocomposites possessed the core-shell structure of good dispersibility, excellent chemical stability, and magnetic property (Ms = 22.11 emu/g). According to the results of series experiments, magnetic TiO2 nanocomposites showed fast kinetics and satisfied adsorption capacity for adsorption of SA. Under the optimum experimental condition, the adsorption process followed pseudo-second-order reaction kinetics and Langmuir adsorption isotherm. Moreover, the thermodynamic parameters calculated from the adsorption data suggested that the adsorption of SA was a spontaneous and endothermic nature of the process. In addition, magnetic TiO2 nanocomposites were proved to exhibit high catalytic efficiency for photodegradation of SA under visible light irradiation, and the intermediate products of photodegradation were inferred from the mass spectrometry.