Experimental data on the relationship between dyes sensitizers and wavelength during the photocatalytic degradation of diclofenac

Sensitizers are being used to improve the photocatalytic activity of semiconductors in the visible light region of the solar spectrum. Different types of dyes are reported as sensitizer agents, such as ruthenium complex molecules, porphyrins and Pt complexes, which are critically assessed because they are hazardous substance. Therefore, it is necessary to replace these compounds with safer sensitizer like organic dyes. This work evaluated the photocatalytic degradation of diclofenac using two different types of organic dyes (Perinaphtenone and Eosin-Y) as sensitizer agents. The catalyst concentration [0.15; 0.35 g/l], source of light (UVA – Vis) and type of dye were evaluated. The data obtained can be useful to classify organic dyes that could be employees as sensitizers and which is the wavelength more adequate to use as an energy source. The Kapp for the reaction has values between 1*10−3 to 5*10−3 min−1 for UVA, 3*10−4 to 3*10−3 min−1 for Vis and 2*10−3 to 6*10−3 min−1 for UV–Vis.

Sensitizers are being used to improve the photocatalytic activity of semiconductors in the visible light region of the solar spectrum. Different types of dyes are reported as sensitizer agents, such as ruthenium complex molecules, porphyrins and Pt complexes, which are critically assessed because they are hazardous substance. Therefore, it is necessary to replace these compounds with safer sensitizer like organic dyes. This work evaluated the photocatalytic degradation of diclofenac using two different types of organic dyes (Perinaphtenone and Eosin-Y) as sensitizer agents. The catalyst concentration [0.15; 0.35 g/l], source of light (UVA e Vis) and type of dye were evaluated. The data obtained can be useful to classify organic dyes that could be employees as sensitizers and which is the wavelength more adequate to use as an energy source. The Kapp for the reaction has values between 1*10 À3 to 5*10 À3 min À1 for UVA, 3*10 À4 to 3*10 À3 min À1 for Vis and 2*10 À3 to 6*10 À3 min À1 for UVeVis.

Data
Data present in this work describes the diclofenac degradation by photocatalysis, photosensitized oxidation, and dye-sensitized of TiO 2 using organic dyes that are a promising technique because of great result has been obtained for the degradation of several contaminants [1e4]. Table 1 shows the properties of all compounds. Fig. 1 presents the UV/vis spectra of the Perinaphtenone (Ph) and Eosin-Y (Ey) dyes used as a sensitizer agent and diclofenac (DFC), this allows knowing the maximum wavelength which absorbs energy each dye and the compound. Fig. 2 and Fig. 3 illustrate the variation of diclofenac (DFC) degradation according to the energy source Visible and UVA light, respectively. Tests of photolysis, photocatalysis and photosensitized oxidation were performed in order to identify synergies. Finally, Fig. 4 and Fig. 5 show the influence of each source of energy for dye-sensitized of TiO 2 for 0.35 gL À1 of catalyst concentration. In the supplementary material the raw data of Figs. 2e4 can be seen. Table 2 shows the experimental conditions and the diclofenac degradation by photolysis, photocalysis and dye sensitization process using Perinaphtenone (Ph) and Eosin-Y (Ey) as sensitizers. Table 3 shows the Kapp for the degradation of DFC by TiO 2 using Perinaphtenone (Ph) and Eosin-Y (Ey) as sensitizers.
Additionally, acetonitrile (Sigma Aldrich, 99.99% analytical grade) and formic acid (Sigma Aldrich, Specifications reagent grade !95%) were used for the mobile phase. For experimental tests water purified by a Millipore Milli-Q device was used.

Reactive system
Photocatalytic reactions were performance is a batch reactor (Pyrex glass bottle) illuminated from the top in a device equipped with six fluorescent tubes interchangeable. UVA light was emitted by tubes TLAD 30W05 Philips with wavelengths between 300 and 450 nm and a maximum at 365 nm [5,6]. Visible lamps Sylvania F30W, emitting above of 400 nm were used. The temperature was kept constant to 27 ± 2 C and air was supplied to each system with a flow rate of 2 L/min to maintain the concentration of dissolved oxygen constant. Fig. 6 shows a scheme of the device.

Experimental
DCF solution was prepared at 30 mg/L. The reaction volume was 0.25 L. TiO 2 concentrations and the dye sensitizer (Eosin Y or Perinaphthenone) were added simultaneously [1,7]. Subsequently, the reactive system was stirred magnetically in darkness for 30 minutes in order to promote the adsorption of DCF and the sensitizer onto the catalyst surface [8,9]. After the adsorption period, the slurry was irradiated for a period of 150 minutes. Aliquots (2 ml) were taken at different intervals to perform analyzes. All tests were repeated three times to ensure the data reproducibility.

Analytical techniques
High-resolution liquid chromatography (HPLC) Thermo scientific ultimate 3000 with a diode array detector (DAD) was used to determine the concentration of DCF using a LiChrosphere® 100 RP-18 column (5mm). A mixture of 35% water (10mM formic acid) and 65% acetonitrile operated in isocratic mode was used as mobile phase at a flow rate of 0.85 mlmin À1 . To obtain the dye spectra UVeVis 1800 spectrophotometer was used.

Acknowledgments
The authors of the paper thank COLCIENCIAS -Colombia for doctoral study funding (Convocatoria 647), to the program and Universidad del Valle -Cali, Colombia for the financial support of this work which was framed within the projects entitled "Evaluaci on de la degradaci on de contaminantes emergentes farmac euticos utilizando TiO2 sensibilizado para el aprovechamiento de la regi on de luz visible".

Conflict of interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.  Table 3 Kapp for diclofenac degradation by photolysis, photocatalysis and dye sensitizartion process os TiO 2.