modification of magnetic tio2 nanocomposite with coiii, znii and niii porphyrins for photodegradation of methylene blue under the blue vis-led light irradiation

The magnetic nanocomposites [magnetite@silica@titania@metallomeso-tetra(hydroxyphenyl)porphyrin, fe3o4@sio2@tio2@mthpp] (msitmp; m = co^iii, zn^ii, ni^ii) and [fe3o4@sio2@tio2] (msit) have been synthesized and characterized. these nanocomposites were used to degrade of methylene blue (mb) under the blue light-emitting diode (led) lamp irradiation. the degradation of mb was monitored by uv-vis spectrometry. upon a 180 min irradiation period maximum degradation of mb in presence of msitni^iip, msitzn^iip, msitco^iiip and msit photocatalysts were 90, 80, 63 and 48% g^-1, respectively. after three 180 min runs, the photocatalysts still exhibited good activity. from ultra-violent-diffuse reflectance spectroscopy spectra, the band gap energies of the photocatalysts were found to be 2.6, 2.5, 2.4 and 2.2 ev for msit, msitco^iiip, msitzn^iip and msitni^iip, respectively. the results consist with the observed relative photocatalytic activity of the photocatalysts which is as follows: msitni^iip > msitzn^iip > msitco^iiip > msit. the higher photocatalytic properties of msitni^iip photocatalyst may be due to the fact that it is more susceptible to receive electron and reach to steady state than that of zn^ii and co^iii complexes. the degradation of mb using these nanocomposites were found to follow the pseudo first order kinetics.