Enhanced photocatalytic performance of Hemin (chloro(protoporhyinato) iron(III)) anchored TiO2 photocatalyst for methyl orange degradation: A surface modification method

TiO2 was prepared by sol-gel method through the hydrolysis of TiCl4 and its surface derivatization was carried out with molecular catalyst like Hemin (chloro(protoporhyinato)iron(III)). Catalyst was characterized by various analytical techniques like UV-vis spectroscopy, FT-IR, FE-SEM and XRD. The anchoring of Hemin on titania surface is confirmed by FT-IR spectra through the linkage of OCOTi bond and also by TGA-DSC and elemental analysis. The photocatalytic activity of the surface modified catalyst is tested for the degradation of methyl orange (MO) as a model compound under UV light. The Hemin impregnated TiO2 (H-TiO2) in presence of H 2O2 shows an excellent photocatalytic activity compared to pristine TiO2, Hemin, H2O2, TiO 2/H2O2, and Hemin/H2O2 systems. The enhancement in the photocatalytic activity is attributed to the presence of iron (III) porphyrin ring on the TiO2 surface, which reduces the electron-hole recombination rate and also by acting as a mediator for continuous production of enriched concentration of hydroxyl radicals along with various other reactive free radicals. © 2013 Elsevier B.V. All rights reserved

Synergistic effect between orthorhombic α-Sulfur and TiO2 as co-photocatalysts for efficient degradation of methylene blue: A mechanistic approach

The synergistic effects between α-Sulfur (α-S) and TiO 2 photocatalysts is studied under UV/solar light. An enhancement in photocatalytic activity was observed under UV light, due to formation of sulfate anions in the reaction mixture and these ions get adsorbed on TiO2 surface by electrostatic force of attraction or it may react with holes/hydroxyl radicals to generate sulfate radical anion. An increase in quantum efficiency is observed with sulfated TiO2 due to reduction in electron-hole recombination rate. The extended response of α-S under visible region is due to non-vertical absorption process, which paved a new way for elemental photocatalysis. © 2014 Elsevier B.V

New Insights into the Origin of the Visible Light Photocatalytic Activity of Fe(iii) Porphyrin Surface Anchored TiO2

In order to utilize visible light more effectively in photocatalytic reactions, the surfaces of TiO2 nanoparticles are sensitized by Hemin molecules (H-TiO2) and the catalyst is characterized by various analytical techniques like powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), UV-Visible absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) with an energy-dispersive X-ray (EDX) technique, BET surface area measurements and thermogravimetric analysis (TGA). The results strongly confirm the chemisorption of Hemin molecules on the TiO2 surface through O&z.dbd;C-O-Ti bonds. The photocatalytic activity of H-TiO2 was investigated by the degradation of 4-nitrophenol as a model compound in an aqueous solution under solar light irradiation with the assistance of an appropriate amount of a sacrificial electron donor. The enhanced activity of H-TiO2 confirms the sensitization process. Intermediate products were identified by HPLC analysis and a possible degradation reaction mechanism was proposed. The development of this porphyrin-based photocatalyst provides an alternative approach in harnessing visible solar light and shows promise for waste water treatment in future industrial applications

Heterogeneous advanced photo- Fenton process using peroxymonosulfate and peroxydisulfate in presence of zero valent metallic iron: A comparative study with hydrogen peroxide photo-Fenton process

The present research work has demonstrated the use of zero valent metallic iron (Fe0) in the photo-Fenton process under the UV illumination as a promising and novel technique. Oxidants like oxone a peroxymonosulfate (PMS) and ammonium persulfate a peroxydisulfate (PDS) were used in comparison with classical hydrogen peroxide (HP). PMS was found to be a better oxidant in comparison with HP and PDS at higher pH conditions especially in the pH range of 5–7. PMS acts as better oxidant with dipolar unsymmetrical structure, higher oxidation potential and its lower LUMO energy can easily accept electrons more readily compared to the other two oxidants. The degradation rate for various oxidation processes at pH 3 shows the following decreasing order: Fe0/PMS/UV ≈ Fe0/HP/UV > Fe0/PDS/UV > HP/UV > PDS/UV> PMS/UV > Fe0/PMS/dark > Fe0/HP/dark > Fe0/PDS/dark > Fe0/UV > Fe0/dark. At pH 5, PMS/UV and PDS/UV systems show similar efficiencies as Fe0/PMS/UV and Fe0/PDS/UV process, since most of the Fe0 surface is covered by the precipitates of hydroxide and oxyhydroxides. Though recycling capability of iron powder is almost comparable for first to fifth repetitions, Fe0 retains its recycling capability better in the presence of HP for the further runs rather than PDS and PMS