Study of adsorption of phenol on titanium oxide (TiO2)

The application of photocatalysis in the treatment of organic micropollutants in wastewater is an interesting alternative and is the object of a great interest over the last years by many researchers. The stage of adsorption of the micropollutant on the photocatalyst, mainly the titanium oxide anatase form, is a determining stage in the process of photodegradation. We present an experimental study of the adsorption of phenol, chosen as the model pollutant, on a photocatalyst, titanium oxide anatase (Degussa P25). The measure of the quantity of phenol adsorbed was made by UV spectroscopy. The equilibrium of adsorption was reached after 1 h; the kinetics of adsorption were slow and obeyed the Lagergrein model. The adsorption was chimisorption in a monolayer and obeyed the Langmuir model. The survey also showed that there was an advantage to operate at great velocity of agitation and a natural pH. The agitation by ultrasonic drives to a light increase of phenol quantity adsorbed (5%) because this mode of agitation reduces the phenomenon of agglomeration of titanium oxide particles and therefore increases the interfacial area of the catalyst.

where all resistance to mass transfer is localized. The fundamental equation to apply is the one that governs the phenomena of mass transfer, in general, between two phases; the flux of adsorption is proportional to the gradient between the quantity adsorbed Q at time t and the adsorbed quantity Qe at equilibrium and a constant Ka (conductance of transfer): The phenol was weakly adsorbed on TiO2. This adsorption is a chimisorption, and it is represented well by the Langmuir model in the studied concentration domain. The aggregation effect of TiO2 in aqueous solution had an optimal concentration of the catalyst for a concentration of phenol. The adsorption was optimal for a pH between 5 and 6 in the neighborhood of the isoelectric point of TiO2.