Available online at www.sciencedirect.comJournal of Hazardous Materials 155 (2008) 45–50Photocatalyzed degradation of flumequine by dopedTiO2and simulated solar lightJ. Nietoa, J. Freerb, D. Contrerasc, R.J. Candald, E.E. Sileod, H.D. Mansillaa,∗aDepartamento de Qu´ ?mica Org´ anica, Facultad de Ciencias Qu´ ?micas, Universidad de Concepci´ on, Casilla 160-C, Concepci´ on, ChilebCentro de Biotecnolog´ ?a, Facultad de Ciencias Qu´ ?micas, Universidad de Concepci´ on, Casilla 160-C, Concepci´ on, ChilecDepartamento de Qu´ ?mica Anal´ ?tica e Inorg´ anica, Facultad de Ciencias Qu´ ?micas, Universidad de Concepci´ on, Casilla 160-C, Concepci´ on, ChiledINQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, ArgentinaReceived 4 July 2007; received in revised form 9 November 2007; accepted 12 November 2007Available online 17 November 2007AbstractTitanium dioxide was obtained in its pure form (TiO2) and in the presence of urea (u-TiO2) and thiourea (t-TiO2) using the sol–gel technique.The obtained powders were characterized by BET surface area analysis, Infrared Spectroscopy, Diffuse Reflectance Spectroscopy and the Rietveldrefinement of XRD measurements. All the prepared catalysts show high anatase content (>99%). The a and b-cell parameters of anatase increasein the order TiO2<u-TiO2<t-TiO2, while the c-parameter presents the opposite trend. Because of the interplay in cell dimensions, the cell growsthicker and shorter when prepared in the presence of urea and thiourea, respectively. The cell volume decreases in the order t-TiO2>u-TiO2>TiO2.The photocatalytic activities of the samples were determined on flumequine under solar-simulated irradiation. The most active catalysts wereu-TiO2and t-TiO2, reaching values over 90% of flumequine degradation after 15min irradiation, compared with values of 55% for the pure TiO2catalyst. Changing simultaneously the catalyst amount (t-TiO2) and pH, multivariate analysis using the response surface methodology was used todetermine the roughly optimal conditions for flumequine degradation. The optimized conditions found were pH below 7 and a catalyst amount of1.6gL−1.© 2007 Elsevier B.V. All rights reserved.Keywords: Antibiotic; Flumequine; Photocatalysis; Sol–gel; Doped titanium dioxide1. IntroductionAntibioticshavebeendesignedtoreducediseases,positivelyimpacting on the quality of life and saving many human livessince their introduction. However, when antibiotics are releasedinto the environment with little control, they can become atremendous problem due to their side effects on natural biotaandthedevelopmentofnewresistantbacteriathatcouldresultinsevere consequences to public health. Antibiotics cannot be nat-urally degraded and conventional secondary effluent treatmentscannotbeconsidered,limitingthepossibilitiestoeliminatethemfrom the environment.Advanced Oxidation Processes (AOPs) have been proposedas a valuable method to degrade refractory organic compoundsdue to the uniqueness of hydroxyl radicals to drive organic∗Corresponding author. Tel.: +56 41 204600; fax: +56 41 245974.E-mail address: hmansill@udec.cl (H.D. Mansilla).matter oxidation rendering high reaction rates and low selec-tivity. Among the AOPs, the photocatalytic method is currentlymentioned as one of the most studied technologies. The pro-cess presents recognized advantages, such as the low price andchemical stability of the more used catalyst (TiO2) and the pos-sibility to combine the process with biological decontaminationmethods [1]. The possibility of using solar light to produce lowmolecular weight and biodegradable compounds has been men-tioned[2].Amongthedrawbacksofphotocatalysisforindustrialapplications commonly mentioned are the design of adequatereactorsforefficientutilizationofphotons,catalystimmobiliza-tion to avoid the filtration step, and the low absorption of lightin the visible region.The large band gap of TiO2(3.2eV) is the main hindranceto a better utilization of the small UV fraction of the solar light(2–3%). To extend the catalysts’ visible light absorption, Ohnoetal.[3–6]recentlysuggestedthemodificationoftitaniabydop-ing the catalyst with non-metallic atoms, such as nitrogen andsulphur. They suggested that sulphur could be incorporated as a0304-3894/$ – see front matter © 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.jhazmat.2007.11.026
