The effect of acetic acid on the photocatalytic degradation of catechol and resorcinol

The photocatalytic degradation of catechol and resorcinol with TiO 2 in presence of acetic acid has been studied. Low concentrations of the acid (30–50 ppm) can modify the adsorption and degradation of the dihydroxybenzenes. However, the acetic acid concentration threshold at which effects are observed depends on the compound. FTIR analyses have shown that due to steric factors, catechol and resorcinol molecules adsorb on different TiO 2 surface centres. Additionally, acetic acid molecules are able to displace Ti 4+ coordinated water molecules and those interacting by hydrogen bonds, to a lesser extent. Consequently, the catalyst surface becomes restructured, favouring the adsorption of the dihydroxybenzenes. The acetates reaction with holes and oxygen molecules with photogenerated electrons to give O 2 − radicals which react with OH groups with acidic character to give new radicals that enhance catechol and resorcinol degradations.