Highly Efficient Degradation of Tartrazine with a Benzoic Acid/TiO₂ System

The roles of benzoic acid and its derivatives in the photocatalytic degradation of tartrazine (TZ) by titanium dioxide have been studied. A series of comparative experiments were carried out, such as the experimental comparisons of concentrations, pH values, effects on the para-position of benzoic acid, gas atmospheres, and different target pollutants. It should be noted that the degradation rate of TZ solution without benzoic acid and benzoic acid after degradation for 90 min was 28.69 and 99.08%, respectively. The reason for the above results is that benzoic acid acts as an electron donor to react with photogenerated holes, suppressing the recombination of photogenerated holes and electrons, and thus causing a significant increase in the degradation rate. Moreover, the degradation process is mainly induced by O₂ ^•- and photogenerated holes (h⁺). It is the first time that the benzoic acid/TiO₂ system has been used to degrade the TZ dye. In addition, the benzoic acid/TiO₂ system is also suitable for the degradation of other organic dyes such as methyl orange, rhodamine B, methylene blue, and methyl violet.