Functionalization of MCM-41 with titanium oxynitride deposited via PECVD for enhanced removal of methylene blue

TiON and TiO2 were grafted onto the surfaces of mesoporous silica MCM-41 by plasma enhanced chemical vapour deposition (PECVD). The results of small-angle X-ray diffraction (SAXRD), X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and nitrogen physisorption revealed that the mesoporous structure of MCM-41 was retained and the pore size reduced from 2.46 nm to 2.19 nm and 2.18 nm after grafting of amorphous TiO2 and TiON, respectively. In consequence, the pore volume and BET surface area decreased. These results indicate the deposition of TiO2 and TiON particles on the surface of MCM-41, leading to partial blockage of its pores. The grafted materials were found to be effective adsorbents for methylene blue dye. The results of batch adsorption experiments at pH 7 demonstrated that TiON@mSiO2 nanocomposite showed the highest adsorption capacity in comparison with MCM-41 and TiO2@mSiO2, which is due to its highly negative zeta potential at neutral conditions. The equilibrium adsorption process fits well with the Langmuir isotherm model and the calculated maximum adsorbed quantity qmax was found to be 129 mg/g. The pseudo-second order model best represents the adsorption kinetics data. Accordingly, the TiON@mSiO2 nanocomposite can be used for the purification of wastewater from toxic organic dyes such as methylene blue. •TiON and TiO2 were grafted onto the surfaces of mesoporous silica MCM-41 by PECVD.•The mesoporous structure of MCM-41 was retained after grafting of TiO2 and TiON.•The grafted materials were found to be effective adsorbents for methylene blue dye.•TiON@mSiO2 composite shows a maximum adsorbed quantity qmax of 129 mg/g for MB dye.•The Langmuir isotherm and pseudo-second order model described the adsorption data.