Some strategies to prepare visible-light responsive TiO2 and their photocatalytic activities towards oxidation and inactivation of waterborne organics and bacteria

JULIÁN ANDRÉS RENGIFO

Belo Horizonte

Congreso; VIII Encontro sobre Aplicaçoes Ambientais de Processsos Oxidativos Avançados e II Congreso Iberoamericano de Processos Oxidativos Avançados; 2015

Universidad Federal de Minas Gerais

During two decades has risen an enormous interestabout the potential of heterogeneous photocatalysis over TiO2 todestroy a wide range of waterborne pollutants and microorganisms. These studieshave positioned this technology as a promising process to wastewaterdetoxification and disinfection [1]. However, nowadays the application of heterogeneousphotocatalysis over TiO2 to water detoxification under solar lightconditions has found several drawbacks to overcome. Among them, the absorptionof visible light represents an enormous limitation in solar-drivenphotocatalytic processes since it is well known that TiO2, in any ofits crystalline structures anatase or rutile, absorbs only UV light, which isnot abundant on the planet´s surface (4-7% of total sunlight hitting the earthsurface) [2].TiO2catalysts with visible light response have been already reported by anchoringof organic or inorganic dyes on the surface of TiO2, doping by metalions and by introducing oxygen vacancies that generate color centers reducingthe band-gap of TiO2 (3.1-3.2 eV) [2, 3]. More recently, anotherapproach has been developed to dope TiO2 with non-metallic speciessuch as N, S and C leading to a spectral shift towards the visible region [2, 4].On the other hand, adding of polyoxometallates(POMs), which are clusters of transition metals and oxygen, on TiO2has also risen as a successfully alternative to synthesize visible lightabsorbing materials with high photocatalytic activity; this latter linked tothe fact that electronic features of POMs could decrease the electron-holerecombination [5, 6].This lecture shows three different strategies (N, Sco-doping of commercial TiO2 powders , sol-gel synthesis of TiO2modified by  POMs and induction of oxygenvacancies on P-25 TiO2 powders by high frequency ultrasound) toprepare TiO2 materials with visible light absorption with highphotocatalytic activity towards organics oxidation and bacteria inactivation inwater.  In addition, it will be also pointed-outthat characterization of these materials by multi-techniques is a capital issuesince it allows a better understanding about limitations and potentials of thesematerials.