Polymorphic Phase Transformation of Degussa P25 TiO2 by the Chelation of Diaminopyridine on TiO62- Octahedron: Correlation of Anatase to Rutile Phase Ratio on the Photocatalytic Activity

A series of nitrogen-doped Degussa P25 photocatalysts were synthesized successfully by grinding and calcination method using 2,6-diaminopyridine (DAP) as a nitrogen precursor. The prepared samples were characterized by various analytical methods. The phase contents of anatase and rutile in the Degussa P25 powders have been altered by simply changing the proportion of DAP. A mechanism involving chelated DAP molecule on TiO62- octahedron is discussed. The enhanced activity is attributed to synergistic effect in the two phase solid material. Due to the low activation barrier, the effective inter particle electron transfer between the two polymorphs is quite efficient only when they are in close proximity with similar crystallite sizes. The transfer of electrons from the rutile phase to lattice/electron trapping sites of anatase and also to the Ti3+-Vo defect level created by the dopant favors effective charge separation and enhance the photocatalytic activity under solar illumination

Kinetic Model Based on non-linear Regression Analysis is Proposed for the Degradation of Phenol under UV/solar Light Using Nitrogen Doped TiO2

Nitrogen was doped into the TiO2 matrix in the concentration range of 0.05-0.20 at.% and the photocatalytic activities were tested for the degradation of phenol (Ph) under UV/solar light using hydrogen peroxide (HP) and ammonium persulfate (APS) as electron acceptors. The prepared photocatalysts characterized by various analytical techniques confirm the incorporation of nitrogen in the TiO2 lattice. The 0.15 at.% dopant concentration shows higher photocatalytic activity compared with sol-gel TiO2 (SG) and Degauss P25 TiO2 (P25) for the degradation process. Photoluminescence technique was used for studying the extent of hydroxyl radicals produced on TiO2 and TiO2−xNx (NT) surface in the presence of oxidants under UV/solar light irradiation. The kinetic rate equation obtained for the best system TiO2−xNx (x = 0.15 at.%)/APS/under solar irradiation is found to be: rap,solar = 0.0041[NT]0.54[APS]0.71[Ph]−0.70. A kinetic/mathematical model was developed based on the nonlinear regression analysis for the various processes and the validity of the model was tested by comparing the experimental values with the theoretically calculated data as a function of variable parameters like catalyst dosage, concentration of electron acceptors and initial concentration of Ph

Influence of various aromatic derivatives on the advanced photo Fenton degradation of Amaranth dye

The photo degrdn. of Amaranth (AR) dye by advanced photo Fenton process in the presence of sym. peroxides like hydrogen peroxide (H2O2) and ammonium persulfate (APS) are investigated. The influence of various reaction parameters like the effect of iron dosage, concn. of H2O2/APS, initial dye concn., effect of pH and the influence of various arom. derivs. were studied and optimum conditions are reported. The efficiency of the oxidant was strongly influenced by the nature of arom. photoproducts formed during the course of the degrdn. reaction. To study their effect on the rate of degrdn. these arom. derivs. were added in known concn. (10 ppm)​. The influence of various arom. derivs. on the degrdn. kinetics shows the following order: hydroquinones > chlorophenol > dichlorobenzene > arom. carboxylic acids > anilidine > nitrophenol. The addn. of these derivs. did not influence the degrdn. pathway although it altered the reaction rate. The percentage COD and TOC removal were detd. in presence of arom. derivs. to evaluate the complete removal of the pollutant. Based on the intermediates obtained in the UV-​vis and GC-​MS spectroscopic techniques probable degrdn. mechanism has been proposed

Photo-degradation of Di Azo Dye Bismarck Brown by Advanced photo-Fenton Process: Influence of Inorganic Anions and Evaluation of Recycling Efficiency of Iron Powder

The present research work has demonstrated the usage of zero valent metallic iron (ZVMI) in the photo-Fenton process under UV light as a promising and novel technique for the complete degradation of di azo dye Bismarck Brown (BB) in aqueous medium. The influence of various reaction parameters like concentration of oxidants/dye/iron powder and pH of the solution was investigated and optimum conditions are reported. Ammonium persulfate (APS) proved to be better oxidant in comparison with hydrogen peroxide for enhancing the degradation rate and effectively inhibited the precipitation of iron hydroxides at higher dosages of iron powder which is attributed to the acidity provided by APS which is crucial for Fenton process. The rate constant for the kinetics of degradation using various oxidation processes follows the order: Fe0/APS/UV > Fe0/H2O2/UV > Fe0/APS/dark > Fe0/UV > Fe0/H2O2/dark > Fe0/dark > H2O2/UV > APS/UV. The effects of inorganic anions that are commonly found in the industrial effluents like NaCl, KNO3, Na2SO4, Na2CO3 and NaHCO3 at different concentrations on the degradation rate were studied in detail. The degradation was followed by UV-vis and GC-MS techniques

Mechanochemical reaction of TiO2 with β-alanine for the preparation of visible light active nitrogen doped titania: Adsorption and kinetic studies

Nitrogen doped TiO2 (TiO2-xNx) with a homogenous anatase phase was synthesized, using β-alanine as a nitrogen precursor and ethanol as a oxygen depriving agent in the concentration range of 0.05, 0.10, 0.15 and 0.2 at and were characterized by Powder X-ray Diffraction (PXRD), X-ray Photoelectron Spectra (XPS), Scanning Electron Microscope (SEM), Fourier Transform Infrared (FT-IR) and UV-visible Diffused Reflectance Spectroscopic (DRS) techniques. Ethanol deprives the surface oxygen, thereby generating oxygen defects whose concentration was evaluated by FTIR, Photoluminescence (PL) and Electron Spin Resonance (ESR) studies. FTIR analysis reveal that concentration of oxygen vacancies/defects (Vo) decreases as the nitrogen concentration increases leading to the reduction in the Ti-O bond length. This results in a shift of the IR absorption peak towards a low wave number as predicted by simple physical harmonic oscillator model. The Ti 2p3/2 XPS spectra of TiO2-xNx shifts to lower binding energies due to the increase in the electron densities around the Ti atoms indicating the formation of Ti3+ in the doped samples. N 2 adsorption-desorption isotherms measurements show a slight increase in the Brunner-Emmet-Teller (BET) surface area, pore diameter, mesopore volume, while the crystallite size and the morphology were also effected by the nitrogen doping. The equilibrium adsorption of Toluene molecules on the photocatalyst surface follows Langmuir theory and the rate controlling step could be the surface reaction of the adsorbed Toluene molecules. © 2011 Springer Science+Business Media, LLC

Metal-metal charge transfer and interfacial charge transfer mechanism for the visible light photocatalytic activity of cerium and nitrogen co-doped TiO2

Nanosized cerium and nitrogen co-doped TiO2 (Ce-TiO2-xNx) was synthesized by sol gel method and characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), FESEM, Fourier transform infrared, N-2 adsorption and desorption methods, photoluminescence and ultraviolet-visible (UV-vis) DRS techniques. PXRD analysis shows the dopant decreases the crystallite sizes and slows the crystallization of the titania matrix. XPS confirm the existence of cerium ion in +3 or +4 state, and nitrogen in -3 state in Ce-TiO2-xNx. The modified surface of TiO2 provides highly active sites for the dyes at the periphery of the Ce-O-Ti interface and also inhibits Ce particles from sintering. UV-visible DRS studies show that the metal-metal charge transfer (MMCT) of Ti/Ce assembly (Ti4+/Ce3+ -> Ti3+/Ce4+) is responsible for the visible light photocatalytic activity. Photoluminescence was used to determine the effect of cerium ion on the electron-hole pair separation between the two interfaces Ce-TiO2-xNx and Ce2O3. This separation increases with the increase of cerium and nitrogen ion concentrations of doped samples. The degradation kinetics of methylene blue and methyl violet dyes in the presence of sol gel TiO2, Ce-TiO2-xNx and commercial Degussa P25 was determined. The higher visible light activity of Ce-TiO2-xNx was due to the participation of MMCT and interfacial charge transfer mechanism