Study On Kintics Of Photocatalysis Oxidation Of Small Molecule Organic Pollutants With Nano-TiO₂ In Water

The photocatalytic degradation kinetics of formaldehyde in UV/TiO₂ suspension system with in-situ monitoring was successfully described by the Langmuir-Freundlich-Hinshelwood (L-F-H) kinetic model. The photocatalytic degradation kinetics of a series of small molecules under different initial concentrations were studied by L-F-H and L-H kinetic model. The influences on the photocatalytic degradation rate constants k such as pH value and co-catalyst were also investigated. The primary contents were listted as follows:(1) This dissertation reviewes the origin and progress of TiO₂ photocatalyticoxidation technology, the reaction mechanism and kinetic model, as well as the influencing factors of photocatalytic degradation rate, and introduces the significance and content of this technology.(2) The photocatalytic degradation kinetics of formaldehyde under different reaction conditions in UV/TiO₂ suspension system was successfully studied by L-F-H kinetic model. The k increases with the increase of initial concentrations,catalyst dosage and light intensity. The k decreases with the increase of solution pH value.(3) To further verify the applicability of the L-F-H model, the photocatalytic degradation kinetics of a series of small molecules under different initial concentrations were studied. The L-F-H model has been proved to be more feasible in describing the kinetic characteristic of the photocatalytic degradation than L-H model.(4) The influences of pH values and co-catalyste concentrations on k were studied by L-F-H model for above substances. The results showed that the k of aldehydes,alcohols,ketones decreases with the increase of pH value. The k of esters decreases firstly and then increases with the increase of pH values. The k of carboxylic acids increases firstly and then decreases with the increase of pH values. The appropriate amount of co-catalyst would speed up the reaction rate.