Photooxidation of an objective compound acridine orange dye（AO） was investigated by using TiO2/Fenton composite system.In the system with pH 3.0

high photocatalytic efficiency was obtained under UV light irradiation.On the contrary

the photocatalytic activity was very limited under visible light irradiation.Through the introduction of surfactant sodium dodecyl sulfate（SDS）

the photocatalytic efficiency could be significantly increased and ultimately the conversion rate could be 91.8% after 30 min irradiation.Based on the dye adsorption model and visible-light sensitized mechanism

the function of SDS is presumed to be attributed to the enhancement of interaction between TiO2 nanoparticles and other molecules（such as dye molecules

intermediate products

and Fenton reagent）.In this way

Fenton reagent played a positive role as competitors in the whole photocatalytic reaction through improving the efficiency of electron transfer from the excited dye molecules to the conduction band of TiO2 as well as Fe3+ ions.In conclusion

the synergistic effect of the two types of reaction occurred in the system in the presence of SDS and made significant contribution to the degradation of dyes.