Correlation of Physicochemical Properties with the Catalytic

Article pubs.acs.org/IECR

Correlation of Physicochemical Properties with the Catalytic Performance of Fe-Doped Titanium Dioxide Powders Andreia Molea,† Violeta Popescu,*,† Neil A. Rowson,‡ Ileana Cojocaru,§ Adrian Dinescu,∥ Adriana Dehelean,⊥ and Mihaela Lazăr⊥

Downloaded by TEXAS A&M INTL UNIV on August 24, 2015 | http://pubs.acs.org Publication Date (Web): July 22, 2015 | doi: 10.1021/acs.iecr.5b00246

†

Physics and Chemistry Department, Faculty of Material and Environmental Engineering, Technical University of Cluj-Napoca, No. 103-105 Muncii Avenue, 400641 Cluj-Napoca, Romania ‡ School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom § University of Craiova, No. 13 Str. Al. I. Cuza, 200585 Craiova, Romania ∥ National Institute for Research and Development in Microtechnologies, 126A Erou Iancu Nicolae Street, 077190 Bucharest, Romania ⊥ National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat, 400293 Cluj-Napoca, Romania ABSTRACT: A simple method for synthesis of Fe-doped TiO2 nanocrystalline powders, namely by coprecipitation, is described in this study. The influence of the iron content on the structural, morphological, optical and photocatalytic properties is determined. On the basis of XRD analysis, it was observed that anatase crystalline phase of TiO2 was stabilized, and the deformation of the elemental cell and strain increase with increasing of iron content due to the substitution of Ti4+ with Fe3+. The substitution process and the interaction between titanium and iron ions was also confirmed from the shifting of the Raman fundamental vibration from 144 to 149 cm−1. The absorption spectra showed that the optical response of TiO2 was red-shifted and the optical energy band gap decreased in the case of low content of Fe, whereas at high content of iron (in this case 3.11%), the optical response is blue-shifted due to the quantum size effect. The photocatalytic performance of Fe-doped TiO2 materials was correlated with the optical energy band gap. Thus, the best photocatalytic performance was obtained for the sample that contains 1.48% iron because it displays the lowest energy band gap (2.79 eV), so the material can absorb radiation from the visible range, even if this sample presents the lowest surface area. The efficiency of the degradation of Methylene Blue dye, under exposure to low intensity ultraviolet and visible radiations was 39%. Based on the characterization and performance of the Fedoped TiO2 materials, it was concluded that the optimal iron content for our studies was 1.48%. radiation from the visible range.9,10 However, Adamek et al.11 presented that only by mixing the iron salts into titanium dioxide suspensions, without doping of the material, the photocatalytic activity increase under UV irradiation, but decrease under visible light irradiation, due to the formation of electrostatic interactions between the surface oxygen anions generated at TiO2 surface, Fe3+ ions and the TiO2 substrate.11 Also, the chemical nature of titanium precursor can affect de photocatalytic performance of the material. Thus, when using titanium organic precursors for synthesis, the organic residue can negatively affect the catalytic performance of the material. Oprea et al.12 reported that the organic residue can block active sites on the titanium dioxide surface which leads to a decrease of the photocatalytic activity of the material.12 Also, a large amount of iron doping material can have a negative effect on photocatalytic activity of TiO2. Thus, at high iron content, the photocatalytic activity of titania doped material decrease due to the increase of the defects and also iron ions can act as recombination centers.7,8,13

1. INTRODUCTION In the last decades, numerous studies have been reported on the application of heterogeneous photocatalysis in the degradation of organic pollutants from wastewaters, using as a catalyst titanium dioxide (TiO2).1−3 However, TiO2 has the ability to decompose the organics by absorbing ultraviolet radiation, its photocatalytic activity under visible light being restricted. To shift the optical response of the TiO2 from the UV range to the visible range, the most promising process reported in the literature is doping with metals.4−7 Among all metals used as doping materials, iron seem to be the most attractive because it is nontoxic, is abundant in nature and has the ionic radius close to ionic radius of the titanium.7−11 The most utilized method for synthesis of Fe-doped TiO2 materials is sol−gel, using titanium organic precursors such as titanium isopropoxide or titanium n-butoxide.8−11 Qamar et al.8 synthesized Fe-doped TiO2 by a sol−gel method using titanium isopropoxide and iron(III) acetylacetonate and reported that with increase of the Fe content, the photocatalytic activity of the materials, under exposure to the visible light irradiation is improved, but decreased under the exposure to the ultraviolet irradiation.8 With the increasing of the iron content from the samples, the optical response of the TiO2 is red-shifted, so, theoretically, the material has the capacity to absorb the © 2015 American Chemical Society

Received: Revised: Accepted: Published: 7346

January 19, 2015 July 9, 2015 July 10, 2015 July 10, 2015 DOI: 10.1021/acs.iecr.5b00246 Ind. Eng. Chem. Res. 2015, 54, 7346−7351

Article

Industrial & Engineering Chemistry Research

UV−vis spectroscopy studies were carried out in order to determine the optical properties of the samples. The total transmittance spectra using Lambda 35 PerkinElmer spectrometer equipped with integrated sphere were measured using Spectralon as a reference. On the basis of the spectra, the energy band gap of the materials was determined using the Tauc’s relation.15


In the present study, a simple method for synthesis of Fedoped TiO2 is reported, using a coprecipitation method, using inorganic precursors of titanium and iron.

2. MATERIALS AND METHODS 2.1. Synthesis of Iron-Doped Titanium Dioxide Powders. Titanium(III) chloride 12.5% (Fisher Scientific) and iron sulfate pentahydrate (Sigma-Aldrich) were used as inorganic precursors. First, titanium hydroxide suspension has been obtained by adding a volume of 13 mL of TiCl3 12.5% that was hydrolyzed in 15 mL of distilled water and 10 mL of H2O2 3% v/v was used for rapid oxidation. The pH was adjusted to 8.5 with 15 mL NH4OH 5% v/v because according to our previous studies;3 at this pH value, the anatase crystalline form of TiO2 is stabilized, after heat treatment. The mixture was stirred for 30 min when a white titanium hydroxide suspension was obtained. In this suspension, 10 mL solutions of Fe2(SO4)3 with different concentrations (0.2%, 0.5% and 1%) was added dropwise. The mixtures were stirred for 24 h. The formed precipitates were filtered, washed several times with distilled water, dried in an oven at 80 °C and treated at 500 °C for 1 h. 2.2. Characterization of Iron-Doped Titanium Dioxide Powders. A quantitative analysis for determination of iron concentration from Fe-doped TiO2 samples was performed by inductively coupled plasma quadrupole mass spectrometry (ICP-Q-MS), using a PerkinElmer ELAN DRC instrument. Calibration standard solutions were prepared by successive dilution of a high purity ICP, multielement calibration standard. For each sample analysis, three replicates were measured. A Bruker AXS D8 diffractometer working with Cu Kα radiation (α = 1.5406 Å) operating in 2θ transmission mode was used to characterize the structural properties of the Fedoped TiO2 materials. X-ray data were collected from 10−60 (2θ) with step size of 0.02. The patterns were evaluated using a standard X-ray powder diffraction data file, JCPDS 12-1272 (space group I41/amd, a0 = 3.785 [Å], c0 = 9.513 [Å]). Using the Powder Cell software, the structural parameters were calculated using the Pseudo-Voigt refinement and the average of crystallite size and strain was calculated by the Williamson− Hall method.14 Total surface areas (St) of the samples were obtained from N2 adsorption−desorption isotherms measured at −196 °C. St was calculated from adsorption branch of the isotherms using the BET model. The isotherms were recorded using a Sorptomatic 1990 apparatus (Thermo Electron Corporation). Prior determination the samples were degassed at 200 °C for 3 h at a pressure of ∼2 Pa, to remove the physisorbed impurities from the surface. Raman spectra of the specimens were obtained using a WiTec Alpha 300 R (LOT Oriel, UK) operating at 0.3 W single frequency 785 nm diode laser (Toptica Photonics, Germany) and an Acton SP2300 triple grating monochromator/spectrograph (Princeton Instruments, USA) over the wavenumber range of 50−3000 cm−1. A confocal Raman microscope was used to determine the characteristic Raman vibrations of the Fe-doped TiO2 powders. Scanning electron microscopy was utilized to characterize the Fe-doped TiO2 powders morphology. The samples were examined using a field emission scanning electron microscope (FE-SEM), Raith e_Line with in-lens electron detection capabilities.

αhν = A(hν − Eg )m

(1)

where α is absorption coefficient, hν is photon energy, Eg is the energy band gap, A is an energy dependent constant and m is an integer depending on the nature of electronic transitions. For the direct allowed transitions, m has a value of 1/2 whereas for indirect allowed transitions, m = 2. The absorption coefficient α was calculated with the following formula:16 α = 2.303·

103A ·ρ c·l

(2)

where A is the absorbance, ρ is the TiO2 bulk density, ρ = 3.84 [g/cm3], c is the concentration of the Fe-doped TiO2 suspensions, c = 1.2 × 10−3 [g/cm3] and l is the path length, l = 1 [cm]. Also, the Urbach energy was determined based on the absorption tail, which can be correlated with the structural disorder and strain caused by the doping impurities:17

⎛ hν ⎞ ln α = α0exp⎜ ⎟ ⎝ EU ⎠

(3)

where α0 is a constant and the EU is the Urbach energy. EU was determined from the slope of ln α versus (hν). 2.3. Photocatalytic Activity of Iron-Doped Titanium Dioxide Powders. For the photodegradation experiments, two lamps were used simultaneously, one with UV emission 6W (300−400 nm) and one with radiation emitted in the visible range 9W (400−700 nm). The intensity of the radiation at the samples surface was 0.183 mW/cm2 measured with Digitales Luxmeter Mavolux 5032C. To study the photocatalytic activity of the Fe-doped TiO2 powders, Methylene Blue dye was degraded. A volume of 50 mL suspensions Fedoped TiO2 that contain 0.01 g catalysts were mixed with 50 mL Methylene Blue solution (46 mg/L). A sample was prepared without the catalyst as a control blank. Prior to exposure to the UV and visible radiation, all the samples were kept in the dark in order to established the adsorption/ desorption equilibrium. The initial concentration of Methylene Blue (MB) and the variation of the concentration with irradiation time in the presence of TiO2 and Fe-doped TiO2 suspensions were measured with a Lambda 35 spectrophotometer using the calibration curve of the dye. The efficiency of the degradation process of the MB in the presence of Fe-doped TiO2 suspensions was calculated with the following formula:18 η% =

0 CMB − CMB 0 CMB

·100 (4)

C0MB

where is the initial concentration of Methylene Blue and CMB is the concentration of MB at a certain irradiation time.

3. RESULTS AND DISCUSSIONS 3.1. Characterization of the Fe-Doped TiO2 Powders. On the basis of ICP-MS quantitative analysis, the concentration 7347

DOI: 10.1021/acs.iecr.5b00246 Ind. Eng. Chem. Res. 2015, 54, 7346−7351

Article


The strain increase while cell parameters on a and c axes decrease with the increase of the iron content due to the substitution of the Ti4+ with Fe3+. The substitution process can be easily realized because the ionic radii of titanium and iron are very close (Ti4+ = 0.68 Å and Fe3+ = 0.64 Å).10 The substitution process can also be justified by the decrease of cell parameters, which implies a decrease of the elemental cell volume and d-spacing on the (101) crystalline plane compared with the standard anatase TiO2. Jaimy et al.19 highlighted the decrease of the cell parameters with the increase of the iron content from the material. The interactions of iron and titanium ions can be also observed from shifting of the Raman fundamental vibration of anatase TiO2 phase. In Figure 2 are presented the Raman


of iron from the samples was 0.63%, 1.48% and 3.11%, respectively. The Fe-doped TiO2 samples were named using the concentration of iron determined by ICP-MS analysis. In Figure 1, the XRD patterns of titanium dioxide and iron doped titanium dioxide powders, after treatment at 500 °C for

Figure 1. XRD patterns of TiO2 and Fe-doped TiO2 powders.

1 h, are presented. According with standard diffraction data file no JCPDS 12−1272 only an anatase phase of TiO2 has been detected, without any diffraction maximum characteristic for iron or iron sulfate used as a precursor to formulation. This can be explained by (i) iron ions are well embedded into a TiO2 matrix, (ii) the iron content cannot be detected because it is under diffractometer detection limits, or (iii) the formed iron compounds can have an amorphous state.7,10 Our data are in good agreement with literature data; thus, Wang et al.9 observed that Fe-doped TiO2 films, with iron content between 5% and 20%, after heat treatment at 500 °C for 1 h, the anatase crystalline phase is obtained and by increasing of the iron content over 20%, the TiO2 films become amorphous, so the iron can inhibit the crystallization process.9 The structural parameters and the average of crystallite size and strain are presented in Table 1. The structural parameters of the samples were compared with a standard anatase titanium dioxide material (JCPDS 12-1272). The average crystallite size tends to increase with the increase of the iron content from 0.63% to 1.48%, but decrease for the sample which contains 3.11% iron. According with BET analysis (Table 1), the lowest surface area correspond to sample which contains 1.48% Fe, namely 85 m2/g; the results are in good correlation with XRD data, namely with the increase of the average crystallite size, the surface area decrease.

Figure 2. Raman spectra of TiO2 and Fe−TiO2 powders, after heat treatment at 500 °C, 1 h.

spectra of the iron doped titanium dioxide powders. The asymmetric tetragonal model of anatase crystalline phase was identified at ∼144 cm−1 (e.g.), 197 cm−1 (e.g), 399 cm−1 (B1g), 519 cm−1 (B1g) and 639 cm−1 (e.g.) Raman mode.20 The Raman modes for iron bonds were not observed. With the increase of the iron content, the Raman peak position shifted from 144 cm−1 to higher wavelength, i.e., 149 cm−1, due to the increasing of the strain induced by the substitution of titanium with iron. Also, the change in Raman peak position and the broadening of the peak can be attributed to the quantum size effect.21 In our case, the sample that contains 3.5% iron exhibits a broadening of the Raman peak compared with the other two samples that can be associated with photon confinement in the nanocrystals.21 SEM microscopy revealed the morphology of the samples (Figure 3). One can observe that after heat treatment, the

Table 1. Structural Parameters Calculated by Pseudo-Voigt Refinement and the Average of Crystallite Size and Strain Calculated by Williamson−Hall of Fe-Doped TiO2 Powders cell parameters sample name

average crystallite size [nm]

strain [%]

a

c

Fe−TiO2 0.63% Fe−TiO2 1.48% Fe−TiO2 3.11% TiO2 JCPDS 12-1272

22 34 25

0.047 0.088 0.194

3.787 3.783 3.780 3.785

9.492 9.488 9.469 9.513 7348

cell volume [Å3] d-spacing on (101) plane [Å] 136.12 135.78 135.29 136.28

3.51(7) 3.51(4) 3.51(0) 3.52(0)

BET surface area [m2/g] 101 85 102


Article



Figure 3. SEM images of Fe−TiO2 powders.

nanoparticles tend to agglomerate, but present a uniform distribution in means of size. For the samples that contain 0.63% and 3.11% iron, it was observed that the particle sizes are near 10−12 nm, whereas for the sample that contains 1.48% iron, the particle sizes are higher, namely, between 15 and 20 nm. The particles sizes of the Fe-doped samples are in good correlation with the BET surface area determination. The sample that contains 1.48% iron has the highest particle size, thus the lowest specific surface area. The UV−vis absorption spectra of the Fe-doped TiO2 powders and determination of the optical energy band gap of the materials are presented in Figure 4. All the samples exhibit absorption maximums in the ultraviolet range, but also present, an absorption broadband in the visible range. In previous work, undoped anatase TiO2 powder has been synthesized using the same procedure described without adding the doping material.22 Comparing the absorption spectra of undoped TiO2 with Fe-doped TiO2 it can be observed a red-shifting of the absorption band from 250 to 300 nm for undoped TiO222 to 350−400 nm for Fe-doped TiO2 samples. Furthermore, the color of Fe-doped TiO2 powders changed from pale reddish to intense reddish (inset in Figure 4, the change of color with increase of iron content of Fe-doped TiO2 powders). A redshifting of the absorbance implies a decrease of the optical energy band gap of the materials from 3.26 eV for undoped TiO2 sample22 to 2.79 eV for Fe-doped TiO2 that contain 1.48% iron. However, a blue-shifting of the absorbance and an increase of the optical energy band gap to 2.97 eV can be

Figure 4. UV−vis absorbance spectra of TiO2 and Fe-doped TiO2 powders. Inset: determination of the optical energy band gap and the color change with the increase of iron content.

observed for the sample that contains 3.11% iron (compared with the sample that contains 1.48% iron). This fact can be attributed to the presence of the amorphous state of iron and/ or to quantum size effect. It is well-known that a decrease of the average crystallite size can induced a blue-shifting of bands in UV−vis absorption spectra.21,23 The quantum size effect for the 7349


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sample that contains 3.11% Fe3+ is illustrated also from Raman peak broadening. The Urbach energy was also determined (Figure 5) and it was observed that with the increase of the iron content, the

Figure 6. Adsorption of Methylene Blue dye on TiO2 and Fe−TiO2 catalysts surface.

Figure 5. Determination of the Urbach energy of TiO2 and Fe-doped TiO2 powders.

Urbach energy increased from 638 meV for the undoped sample to 1372 meV (for the sample that contains 0.63% Fe) and 2454 meV (for the sample that contains 3.11% Fe), due to the increasing of the strain from 0.047% to 0.194%, caused by the substitution process. After characterization of the Fe-doped TiO2 powders, we can conclude that the optimal dopant content in these studies was 1.48% because it has the lowest optical energy band gap and, theoretically, the material can absorb radiation from the visible range. 3.2. Degradation Process. Photocatalysis process occurs on the surface of titanium dioxide-based catalysts. The decreased of pollutants concentrations in aqueous solutions is due to the both effects, namely adsorption processes and photocatalysis, respectively. To demonstrate the photocatalytic properties, a clear distinction between adsorption and photocatalysis the processes is necessary. Therefore, in the first stage of the study, the adsorption process of the dye on catalysts surface under dark conditions, was investigated. On the basis of the adsorption data (Figure 6), it was established that a very small amount of the dye is adsorbed on catalysts surface. Also, on the basis of the adsorption data, it was observed that the equilibrium is established after 1 h in dark conditions. The photocatalytic performance of Fe-doped TiO2 materials was studied by degradation of MB dye with exposure to both UV and visible radiation. From the degradation experiments (Figure 7), it was observed that the highest photocatalytic performance is presented by the sample that contains 1.48% iron with an efficiency of MB degradation of 39%. The samples that contain 3.11% and 0.63% iron have an efficiency of 30% and 28%, respectively. Comparing the data with the photocatalytic performance of the undoped TiO2, which presents an efficiency in the degradation of MB of 28%,22 at low content of iron (i.e., Fe-doped TiO2 0.63%), no improvement of the photocatalytic performance of the material has been observed and at high concentration of iron content (3.11%) the performance decreased even if the mentioned samples exhibits

Figure 7. Photodegradation process of the MB in the presence of TiO2 and Fe-doped TiO2, under both UV and visible radiation.

higher surface area than the sample doped with 1.48% iron. In the case of the sample doped with 3.11% iron, the metal can act as a recombination center due to the higher formation of the defects into the TiO2 matrix.8 For the blank sample (without catalyst), no change in concentration of MB as a function of irradiation time was observed. The photodegradation results were correlated with the energy band gap of the Fe-doped TiO2 materials. Thus, the sample that contains 1.48% iron presents the lowest optical energy band gap, so the material can absorb radiation from the visible range, enhanced the photodegradation process.

4. CONCLUSION This paper reports a simple method for the synthesis of Fedoped TiO2 nanocrystalline powders, without using complex apparatus or operating conditions. The structural, morphological, optical and photocatalytic performance of the materials and the correlation of the physicochemical properties with the iron content were performed. Thus, on the basis of XRD analysis, it was observed that anatase TiO2 stabilized, but with increase if iron content, the deformation of the elemental cell and strain increases due to the substitution of Ti4+ with Fe3+. 7350


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photocatalytic activity of iron-doped TiO2. J. Mol. Catal. A: Chem. 2013, 366, 222. (11) Adamek, E.; Baran, W.; Sobczakb, A. Effect of FeCl3 on the photocatalytic processes initiated by UVa and vislight in the presence of TiO2−P25. Appl. Catal., B 2015, 172, 136. (12) Oprea, O.; Ghitulica, C. D.; Voicu, C.; Vasile, B. S.; Oprea, A. Synthesis and photocatalytic properties of Fe(III) - doped TiO2 prepared by sol-gel method. Rev. Rom. Mater. 2013, 43 (4), 408. (13) Ruggieri, F.; Di Camillo, D.; Maccarone, L.; Santucci, S.; Lozzi, L. Electrospun Cu-, W- and Fe-doped TiO2 nanofibres for photocatalytic degradation of rhodamine 6G. J. Nanopart. Res. 2013, 15, 1982. (14) Kraus, W.; Nolze, G. POWDER CELL - a program for the representation and manipulation of crystal structures and calculation of the resulting X-ray powder patterns. J. Appl. Crystallogr. 1996, 29, 301. (15) Tauc, J.; Grigorovici, R.; Vancu, A. Optical Properties and Electronic Structure of Amorphous Germanium. Phys. Status Solidi B 1966, 15, 627. (16) Serpone, N.; Lawless, D.; Khairutdinovt, R. Size Effects on the Photophysical Properties of Colloidal Anatase TiO2 Particles: Size Quantization versus Direct Transitions in This Indirect Semiconductor? J. Phys. Chem. 1995, 99, 16646. (17) Kang, S. H.; Lim, J. W.; Kim, H. S.; Kim, J. Y.; Chung, Y. H.; Sung, Y. E. Photo and Electrochemical Characteristics Dependent on the Phase Ratio of Nanocolumnar Structured TiO2 Films by RF Magnetron Sputtering Technique. Chem. Mater. 2009, 21, 2777. (18) Caliman, A. F.; Cojocaru, C.; Antoniadis, A.; Poulios, I. Optimized photocatalytic degradation of Alcian Blue 8 GX in the presence of TiO2 suspensions. J. Hazard. Mater. 2007, 144, 265. (19) Jaimy, K. B.; Baiju, K. V.; Ghosh, S.; Warrier, K. G. K. A novel approach for enhanced visible light activity in doped nanosize titanium dioxide through the excitons trapping. J. Solid State Chem. 2012, 186, 149. (20) Boukrouh, S.; Bensaha, R.; Bourgeois, S.; Finot, E.; Marco de Lucas, M. C. Reactive direct current magnetron sputtered TiO2 thin films with amorphous to crystalline structures. Thin Solid Films 2008, 516, 6353. (21) Balaji, S.; Djaoued, Y.; Robichaud, J. Phonon confinement studies in nanocrystalline anatase-TiO2 thin films by micro Raman spectroscopy. J. Raman Spectrosc. 2006, 37, 1416. (22) Molea, A.; Popescu, V.; Rowson, N. A. Effects of I-doping content on the structural, optical and photocatalytic activity of TiO2 nanocrystalline powders. Powder Technol. 2012, 230, 203. (23) Strauss, M.; Pastorello, M.; Sigoli, F. A.; de Souza e Silva, J. M.; Mazali, I. O. Singular effect of crystallite size on the charge carrier generation and photocatalytic activity of nano-TiO2. Appl. Surf. Sci. 2014, 319, 151.


The substitution process and the interaction between titanium and iron ions was also emphasized by the shifting of the Raman fundamental vibrations. The optical spectra showed that with increase of the iron content the optical response of TiO2 was red-shifted from the ultraviolet range to the visible range and the optical energy band gap decrease, but at high iron content (in this case 3.11%) the optical response is blue-shifted due to the quantum size effect. The optimal iron content was found to be 1.48% in this study. The photocatalytic performance of Fe-doped TiO2 materials was correlated with the optical energy band gap. The best photocatalytic performance was obtained for the sample doped with 1.48% iron because has the lowest energy band gap (2.79 eV), so the material can absorb radiation from visible range, even if this sample presents the lowest specific surface area. The efficiency of the degradation of Methylene Blue dye, under exposure to low intensity ultraviolet and visible radiations was 39%.

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AUTHOR INFORMATION

Corresponding Author

*Violeta Popescu. E-mail: [email protected]. Tel: 0040 264401778. Fax: +40 264493333. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This paper was supported by the Post-Doctoral Programme POSDRU/159/1.5/S/137516, project cofunded from European Social Fund through the Human Resources Sectorial Operational Program 2007-2013.

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REFERENCES

(1) Liu, Y.; Hua, L.; Li, S. Photocatalytic degradation of Reactive Brilliant Blue KN-R by TiO2/UV process. Desalination 2010, 258, 48. (2) Kwon, S.; Fan, M.; Cooper, A. T.; Yang, H. Photocatalytic applications of micro-and nano-TiO2 in environmental engineering. Crit. Rev. Environ. Sci. Technol. 2008, 38, 197. (3) Molea, A.; Popescu, V.; Rowson, N. A.; Dinescu, A. M. Influence of pH on the formulation of TiO2 nano-crystalline powders with high photocatalytic activity. Powder Technol. 2014, 253, 22. (4) Khraisheh, M.; Wu, L.; Al-Muhtase, A. H.; Albadarin, A. B.; Walker, G. M. Phenol degradation by powdered metal ion modified titanium dioxide photocatalysts. Chem. Eng. J. 2012, 213, 125. (5) Liqiang, J.; Honggang, F.; Baiqi, W.; Dejun, W.; Baifu, X.; Shudan, L.; Jiazhong, S. Effects of Sn dopant on the photoinduced charge property and photocatalytic activity of TiO2 nanoparticles. Appl. Catal., B 2006, 62, 282. (6) Harikishore, M.; Sandhyarani, M.; Venkateswarlu, K.; Nellaippan, T. A.; Rameshbabu, N. Effect of Ag doping on Antibacterial and Photocatalytic Activity of Nanocrystalline TiO2. Procedia Mater. Sci. 2014, 6, 557. (7) Ambrus, Z.; Balazs, N.; Alapi, T.; Wittmann, G.; Sipos, P.; Dombi, A.; Mogyorosi, K. Synthesis, structure and photocatalytic properties of Fe(III)-doped TiO2 prepared from TiCl3. Appl. Catal., B 2008, 81, 27. (8) Qamar, M.; Merzougui, B.; Anjum, D.; Hakeem, A. S.; Yamani, Z. H.; Bahnemann, D. Synthesis and photocatalytic activity of mesoporous nanocrystalline Fe-doped titanium dioxide. Catal. Today 2014, 230, 158. (9) Wang, M. C.; Lin, H. J.; Yang, T. S. Characteristics and optical properties of iron ion (Fe3+)-doped titanium oxide thin films prepared by a sol−gel spin coating. J. Alloys Compd. 2009, 473, 394. (10) Deng, F.; Luo, X.; Li, K.; Tu, X.; Luo, S.; Yang, L.; Zhou, N.; Shu, H. The effect of vinyl-containing ionic liquid on the 7351


Correlation of Physicochemical Properties with the Catalytic

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