An insight into the adsorption and photocatalytic degradation of rhodamine B in periodic mesoporous materials

The present study explores the different modes of adsorption of rhodamine B dye over two different siliceous (Si-MCM-48 and Si-MCM-41) and titania loaded siliceous (Ti-MCM-48 and Ti-MCM-41) mesoporous materials. The equilibrium adsorption studies indicate that siliceous as well as Ti-loaded mesoporous materials are good adsorbents for the removal of rhodamine B dye from aqueous solutions, and an enhanced uptake was obtained with siliceous than the titania loaded mesoporous materials. The adsorption data were fitted with different isotherms, and it was observed in general that the dye molecules obeyed Langmuir type of adsorption. The presence of rhodamine B dimer was evident from DRS analysis, and the J-dimer formation of rhodamine B molecules was proved by photoluminescence (PL) studies. In addition, the degradation of rhodamine B dye over titania loaded and siliceous mesoporous materials indicate that Ti-MCM-41 is more effective than Ti-MCM-48, whereas only decoloration of the dye was observed in both of the siliceous materials. Furthermore, Ti4+ in tetrahedral coordination plays a vital role in enhancing the degradation efficiency, and the degraded products were identified by using electrospray ionization-mass spectrometry (ESI-MS) studies. (C) 2015 Elsevier B.V. All rights reserved.