Chemometric investigation of the efficiency of different TiO2-based catalysts as principal components of TOC photochemical sensors under development

• Autores: Luigi Campanella, Giovanni De Angelis, Giovanni Visco
• Localización: Analytical and bioanalytical chemistry, ISSN 1618-2642, Vol. 376, Nº 4, 2003, págs. 467-475
• Idioma: alemán
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• Resumen

  • There is an increasing demand for measurement of organic carbon in solutions both in industry and in environmental research for the purpose of continuous water-quality monitoring. Practically all the methods used are based on a catalytic system in which metal oxides play a major role. The development of a new TOC/DOC measurement system, in our work, uses a mixed anatase–rutile form of TiO2 as catalyst of the mineralisation process, and direct measurement of the CO2 produced, by a gaseous diffusion electrode. The entire research is based on heterogeneous catalysis using an immobilised catalyst, which can offer considerable advantages over other methods of catalysis. Four different catalytic systems were analysed. Three involved thermal immobilisation of TiO2 on glass supports (glass spheres and glassy particulates) or on an Al metal grid. One further system consisted of direct oxidation of a Ti grid at high temperatures. The system was illuminated using a 350 nm UV source (350 mW cm−2) contained in a home-made measurement cell. Five molecules—malic acid, pentachlorophenol, sodium dodecylsulfate, hydroquinone, and citric acid—which were deemed to be representative and had been investigated in several previous studies, were used as photodegradation targets. However, it was not possible to obtain a direct expression of "catalytic efficiency" simply by reading the data obtained, nor any indirect molecular "recalcitrancy" scale. Chemometric analysis, by principal components analysis, allows the five used catalytic systems to be easily compared each other and a single PC component is able to perform classification.