Fabrication of a reusable magnetic multi-walled carbon nanotube-TiO2 nanocomposite by electrostatic adsorption: enhanced photodegradation of malachite green

A simple, quick and efficient method for the fabrication of a magnetic multi-walled carbon nanotube-TiO2 (MMWCNT-TiO2) nanocomposite through electrostatic attraction was proposed as a novel method. First of all, TiO2 nanoparticles were synthesized by an atmospheric pressure chemical vapor synthesis (APCVS) method and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-Vis diffuse reflectance spectroscopy (DRS). Next, the magnetic multi-walled carbon nanotube (MMWCNT) nanocomposite was prepared. Finally, TiO2 nanoparticles were coated onto the surface of the MMWCNT through electrostatic attraction in ethanol solution. The morphology and structure of the final composite were investigated by SEM, XRD, Energy dispersive X-ray spectrometry (EDS) and Fourier transform infrared spectrophotometry (FT-IR). Both TiO2 and MMWCNT-TiO2 were characterized by BET surface area/pore volume analysis. The photocatalytic function of the TiO2 and MMWCNT-TiO2 composite was validated for malachite green (MG) degradation under irradiation with ultra violet (UV) light. MMWCNT-TiO2, adsorbing MG, was easily separated from the aqueous solutions with the help of an external magnet; so, no filtration or centrifugation was necessary. The effects of pH, irradiation time, catalyst concentration, MG concentration, etc. on the photocatalytic activity were studied. The optimal conditions were an initial MG concentration of 20 mg L-1 at pH 5.0 with a catalyst concentration of 0.2 g L-1 under UV irradiation for 240 min with good recyclisation of the MMWCNT-TiO2 catalyst.