(716b) Degradation of of Rhodamine B Dye Over Mn-Doped Titania Nanotubes

Mn-doped titania nanotubes were fabricated by solution combustion synthesis followed by the hydrothermal treatment in the removal of Rhodamine B, a dye. Combustion synthesis has emerged as a facile and economically viable technique for the preparation of advanced ceramics, catalysts and nanomaterials. Stoichiometric amounts of transition metal nitrates and fuel (Glycine) are mixed in a solution for the preparation of nanomaterials by using the single step solution combustion method at 350° C. The Mn_xTi_(1-x) O_(2-δ) (x ranges from 0.05-0.25) nanomaterials are made in the anatase phase by the solution combustion synthesis. The nanotubes are then fabricated using the hydrothermal method using 10 N NaOH at temperature of 130°C for 24 hours.

The prepared Mn-doped titania nanotubes were characterized using JEOL 2100 field emission Gun Transmission Electron Microscope (JEM 2100F TEM) and HITACHI S-3400 N Scanning Electron Microscope (SEM) attached with Energy Dispersive X-ray Spectrometry (EDX).  X-ray diffraction (XRD) analysis was performed on a Bruker D8 Focus diffractometer equipped with a Sol-X detector using a copper radiation source, and specific surface area analysis was done using the Brunauer, Emmett, and Teller (BET) method based on N₂ adsorption at 77 K with a NOVA 1000 series analyzer. The thus prepared Mn-doped titania nanotubes contain both monoclinic and anatase phases as evidenced by the XRD and EDX results.  The surface area for the nanotubes decreases with increased doping of Mn.  Further, TEM analysis shows the formation of nanotubes, which are open ended and are approximately 100-120 nm length with inside and outside diameter estimated to be 6 nm and 12 nm.

 The UV-Vis spectrum for the degradation of 4 ppmw Rhodamine B (RhB) over the 0.1 g (0.067 wt %) Mn_0.15Ti_0.85O_(2-δ)  nanotubes shows the successive blue shift from the absorption peak  at 554 nm (Rhodamine B) to 498 nm (Rhodamine), indicating the stepwise N’de-ethylation from dark pink to light green. All the experiments were conducted in dark without external energy supply. Degradation of Rhodamine B follows a second order kinetics as shown by the linear plots between 1/C_a vs time. 15% Mn is the optimum doping with the hioghest degradation rate constant. The activity of Mn_0.15Ti_0.85O_(2-δ)  increases with temperature with an activation energy of 40777 kJ/kmol for the degradation of RhB.