Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

PP-III-3Afterward, a 30% aqueous hydrogen peroxide solution was gradually added to the soobtained white aqueous Ti(OH) 4 gel, to induce the formation of a yellow titanium peroxidesolution. PS sheet samples, previously cleaned with diluted nitric acid, ethanol and deionizerwater, were coated by dipping them into the obtained titanium hydroxide gelified solution.Both a room temperature and a mild heat treatment have been applied, to allow TiO 2formation, confirmed by XRD analysis. The photocatalytic performance of the obtainedcoatings was benchmarked vs. a coating of γ-Al 2 O 3 powders obtained by Aldrich (99,8%purity). To achieve controlled and repeatable exposure conditions, a UV test cell was used,equipped with a 300W UV-A lamp. To avoid excess of substrate heating up, forcedventilation of the samples was ensured by a fan. Organic dyes were used as chemicalcompounds to be degraded bythe photocatalythic activity oftitania coating [3-6]. Theselected dyes, used in differentconcentrations (0.4% w/wsolution, further diluted 100and 1000 folds), wereMethylene Blue, Methyl Red,Ortho-CresoleRed,Fig. 1. Colorimetric analysis of photocatalytic effects on Eosin andRhodamine-B, Eosin, Bengal Rhodamine-B; TiO 2 and γ-Al 2 O 3 coating performance comparisonRose. Samples were soiled byequal dyes solution volumes (1 cm 3 ). The results were evaluated by colorimetric analysis:RGB pixel values were averaged over sample image, and normalized using a standard sample(uncoated PS) as baseline; higher colorimetric indexes indicate color whitening, hence dyedecomposition. Clear photocatalytic effect (dye discoloring) was detected on coated samples,comparable with anatase powder ones, and significantly higher than alumina reference; sucheffect was quantified by colorimetric data as shown in Fig. 1, where titania coating comparedwith γ-Al 2 O 3 effectiveness over Eosin and Rhodamine B is shown. Slight discoloring inalumina coated samples can be related to direct UV light action on dyes.References1. S. Ogata & Y. Matsui, US patent application, 20010019776A1.2. S. Ogata & Y. Matsui, US patent, 6107241.3. E. Bizani, K. Fytianos, I. Poulios, & V. Tsiridis, Journal of Hazardous Materials, 136, 85–94 (2006).4. M. Qamar, M. Saquib, & M. Muneer, Desalination, 186, 255–271 (2005).5. S.B. Bukallah, M.A. Rauf, & S.S. Ashraf, Dyes and Pigments, 72, 353–356 (2007).6. C.G. da Silva & J.L. Faria, Journal of Photochemistry and Photobiology A: Chemistry, 155, 133–143(2003).308