Why is the photocatalytic degradation rate of phenol in acidic pH more than its rate in basic pH?
Thanks for the contribution in advance.
According to the PZC the catalyst can be on the stable state or a ionic one, the pH up to PZC the TiO2 catalyst is on a dissociated form.
Article Photo-degradation of butyl parahydroxybenzoate by using TiO2...
A simplistic answer would be the following: under acid conditions, below the PZC of the catalyst, its surface is plenty of OH groups. UV irradiation promotes an electron from them to the semiconductor valence band, producing OH radicals quite easily... Under normal basic conditions phenol remains protonated, so that it would not have any effect on oxidation.
It depends on the zero point charge of the catalyst. And also in acidic condition the aromatic structure of phenol is easily cleaved by photocatalysis.
I agree which K. Vignesh and also the pKa of phenol about 10 and if the pH solution of degradation process is lower than this value , the phenol will resale as negative and more than will be positive and then the zero pint charge the second effect on degradation process. If the surface of catalyst postie and the phenol is negative at the pH is lower than pKa , it will be adsorb of phenol on to catalyst surface which enhance of degradation process.
regards
- Badges
- Science method