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Evaluation of Photocatalytic Active Coatings on Sintered Glass Tubes by Methylene Blue

DOI: 10.1155/2013/614567

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A comparative study between ten different photocatalytic active coatings was done. The effectiveness and photocatalytic activity of the coatings were studied by degradation experiments of methylene blue (MB) dye under UV light illumination. The reactor design consisting of sintered glass packed in a borosilicate tube placed between two planar dielectric barrier discharge lamps (Osram Planon) is reported for the first time. The coatings consisted of either titania, silica, or zinc on sintered borosilicate glass. The advantage of sol-gel in catalyst preparation was exploited to combine catalyst to act as cocatalyst. TiO2-P25 widely applied in suspension systems was effectively immobilized on sintered glass support with the aid of tetraethylorthosilicate (TEOS) solution which acted as support material. Results indicated that TiO2-P25+SiO2, TiO2-P25+SiO2+Pt, and TiOSO4_30,6wt% films showed highest degradation rates close to 100% after 90?min illumination with degradation rates exceeding 50% after 30?minutes. TTIP+Pt showed lowest degradation rate. 1. Introduction The textile and chemical industry face the challenge to adequately dispose their waste water. Releasing chemicals and colored waste water in the ecosystem is a source of pollution and damage to aquatic life. In order to treat waste water physicochemical methods such as adsorption [1], chemical methods such as chlorination and ozonation [2], and biological methods [3] are the most frequently used approaches. The catalytic system can either be homogeneous or heterogeneous. In a heterogeneous system, both adsorption and photocatalysis take place and have major advantages such as reuse of catalyst; minimization of catalyst leaching or resistance to extreme physical and chemical conditions. A heterogeneous system is tested in this study with use of coatings produced through sol-gel basis on sintered glass in a borosilicate glass tube. Currently most photocatalytic reactors used for water treatment are suspension reactors with the advantage of high catalytic efficiency [4]. However, the catalyst particles have to be recovered after reaction through means such as ultrafiltration which bring along an additional process step and higher cost. Also, particulate matter may accumulate in the reactor during the concentration of a process effluent. Due to these reasons, a photocatalytically active layer on a support material is of growing interest. The setbacks of immobilized system are the less photonic efficiency values attained compared to suspension reactors because of mass transfer limitation [5]. For a good


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