1. 3rd EUROPEAN CONFERENCE ON ENVIRONMENTAL APPLICATIONS
OF ADVANCED OXIDATION PROCESS, ALMERIA (SPAIN), OCTOBER 2013
Efficiency of heterogeneous photo-catalysis (TiO2) for the removal of an acidic pharmaceutical from liquid phase: case study Diclofenac sodium
S. Khalaf1,2, L. SCRANO2,F. LELARIO1, S. A. BUFO1 and R. KARAMAN3
1 Department of Science, 2Department of European cultures (DICEM), University of Basilicata, , Potenza, Italy.
3 Faculty of Pharmacy, Al-Quds University, Jerusalem, Palestine.
Photoproducts of irradiated samples were detected by LC/FTRCR-ESI-MS. Electrospray (ESI)-MS spectra were obtained for all diclofenac sodium photoproducts, which were identified as shown in figure 3. three detected metabolites were detected as listed in Table 2. .
Introduction
purchased from Macherey-Nagel (Germany). All the solutions were daily prepared in ultra-pure water from a Millipore purification system.
Instrumentations and methods : The photocatalytic experiment was performed under irradiation of 1.8 KW Xenon Arc lamp fitted with a quartz glass filter with a UV cut-off at 290 nm (Heraeus Suntest CPS Instrument) Fig.1, the reaction mixture in the reactor was maintained in suspension by magnetic stirring. Extreme care was taken to ensure uniform experimental conditions during the degradation rate determination. At specific time intervals, samples of 2 ml were withdrawn. Then filtered by Millipore filters and analyzed using high performance liquid chromatography system (HPLC) (Agilent technologies 1200 series) equipped with an Eclipse XDB-C18 (3 μm particle size, 4.6 mm × 150 mm) column (Phenomenex-USA) at λ = 254 nm. The identification of metabolites was performed using an using an LC system coupled to a hybrid linear quadrupole ion trap (LTQ) – Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer (Thermo Fisher Scientific, Germany).
Pharmaceuticals compounds (PhCs) have been identified and detected in wastewater, river water and even sewage sludge and soil at ng/L levels, which may cause a potential hazard for the aquatic environment [1]. And since PhCs are not able to eliminated by traditional wastewater treatment plants, due to their low biodegradability and high chemical stability [2], an enhanced technologies such as advanced oxidation processes (AOPs) have been employed to reduce it is presence in the aquatic environment, AOPs can be defined as an oxidation processes based on generating highly reactive species such as hydroxyl radicals (·OH) which are able to oxidize and mineralize almost all kinds of organic compounds such as pharmaceuticals [3]. Among all technologies of AOPs employed in wastewater treatment field, heterogeneous photo-catalysis with semiconductors is the most popular and effective one. In heterogeneous photo-catalysis, dispersed solid particles of semiconductor efficiently absorb large fractions of the UV spectrum, and they generate chemical oxidants from dissolved oxygen or water in situ [4], TiO2 was generally demonstrated to be the most active semi-conducting materials, since it is strong resistance to chemical- and photo-corrosion, safety and low cost and it can use natural (solar) UV because it has an appropriate energetic separation between its valence bands and conduction bands, which can be surpassed by the energy content of a solar photon (λ> 300 nm) [5].
The aim of this work is to evaluate the efficiency of heterogeneous photo-catalysis/TiO2 for the removal of acidic non-steroidal anti-inflammatory drugs (NSAIDs) called Diclofenac sodium through a batch experiment, which performed under sun light irradiation (solar simulator), the kinetic studies of the photodegradation process was accomplished, then the arising photoproducts have been detected and identified using liquid chromatography coupled with mass spectrometry (LC-MS).
Fig.1: Suntest CPS (solar simulator) device.
Results and discussion
The decline in concentration for Diclofenac sodium with increasing irradiation time in the experiment followed first order kinetics, as given in Fig.2, which are confirmed by the linear behaviour of ln CA (t) as a function of irradiation time, all kinetic parameters are listed in Table 1
Fig.3: Photocatalytic degradation pathway for diclofenac sodium
Table 2: Compounds identified as [M+H]+ by LC–ESI-FTICR MS.
Compound no.
Molecular formula
Accurate m/z [M+H+]
RT min.
Error (ppm)
(1)
C14H11NO2Cl2
25.31
(2)
C14H10O3NCl2
9.06
(3)
C14H9O3NCl
5.56
(4)
C14H9NO2Cl
15.71
References
[1] G. Oron, L. Gillerman, A. Bick, N. Buriaskovsky, M. Gargir, Y.Dolan, Y.Mnoar, L. Katz and J. Hagin. Membrane technology for advanced wastewater radiation, Desalination, 2008, 218,
[2] K. Maria, M. Dionissios, K. Despo. Removal of residual pharmaceuticals from aqueous systems by advanced oxidation processes
[3] Y. Lin, C. Ferronat, N. Deng, J.Chovelon. Study of benzylparaben photocatalytic degradation by TiO , (353–360).
[4] X. Zhu, C. Yuan, Y. Bao, J. Yang, Y. Wu. Photocatalytic degradation of pesticide pyridaben on TiO2 particles. 2005, 95–105.
[5] C.Wu. Effects of operational parameters on the decolorizationod C.I Reactive Red 198 in UV/TiO2-based system. 2008,
Fig 2: Degradation kinetics of diclofenac sodium under suntest light with TiO2
Experimental
Table 1: Kinetic parameters of photocatalytic process with TiO2.
Chemicals and materials: Diclofenac sodium pure standard (>99%) was obtained from Birzet Pharmaceutical Company (Palestine), TiO2 P-25 from Degussa, acetonitrile, formic acid and water for analysis were for HPLC grade and purchased from Sigma Aldrich, Millipore filters (0.2 µm pore size, filter-Ø: 25mm)
No.
Parameters
Results 1
Rate constant k (min-1)
0.012 2
Half-life t1/2 (min)
54.6 3
R (%)
99.4
Acknowledgements
This work was supported by the European Commission in the framework of the Project “Diffusion of nanotechnology based devices for water treatment and recycling- NANOWAT” (ENPI CBC MED
I-B/2.1/049, Grant No. 7/1997).