Removal of Congo Red by magnetic mesoporous titanium dioxide–graphene oxide core–shell microspheres for water purification

Abstract

Magnetic mesoporous titanium dioxide–graphene oxide (Fe₃O₄@mTiO₂@GO) with a large surface area and a good magnetic responsiveness was synthesized by immobilizing a mesoporous titanium dioxide (mTiO₂) shell on the surface of magnetic Fe₃O₄ nanoparticles prior to binding with graphene oxide (GO). It showed a tunable pore structure and surface properties, and was mechanically strong. The characteristic results of a Fourier transform infrared spectrometer (FTIR), a scanning electron microscope (SEM), a vibrating sample magnetometer (VSM) and X-ray diffraction (XRD) indicated that Fe₃O₄@mTiO₂@GO has been prepared. Fe₃O₄@mTiO₂@GO was used as an adsorbent for the removal of Congo Red (CR) from simulated wastewater with a fast solid–liquid separation in the presence of an external magnetic field. Batch adsorption experiments were performed to evaluate the adsorption conditions and reusability. The results showed that the maximum adsorption capacity was 89.95 mg g⁻¹, which is much higher than the previously reported values of other absorbent materials. Moreover, the Fe₃O₄@mTiO₂@GO could be repeatedly used via simple treatment without any obvious structure and performance degradation. The adsorption kinetic data were best described by a pseudo-second-order model and the equilibrium adsorptions were well-described by the Freundlich isotherm model. The Fe₃O₄@mTiO₂@GO may be suitable materials for use in CR pollution cleanup if synthesized on a large scale and at a low price in the near future.