The photocatalysts of perovskite type sulfate modified titanium-bearing blast furnace slag were prepared by the high energy ball milling method.With the aid of FT-IR

the photocatalysis mechanism of sulfate modified titanium-bearing blast furnace slag was discussed.The effect of different acidities and acidic media on the photocatalytic reduction of Cr (Ⅵ) by sulfate modified titanium-bearing blast furnace slag was investigated.The results showed that acidity and acidic medium affected the photocatalytic reduction efficiency of Cr (Ⅵ) in aqueous solution.Under strong acid condition (pH=1.5)

the photocatalytic reduction efficiency of Cr (Ⅵ) reached a maximum.With increasing pH of the solution

the photocatalytic reduction efficiency of Cr (Ⅵ) decreased obviously. The order of the stimulative effect of different acidic media was PO43-＜NO3-＜Cl-＜SO42-;after photocatalytic reduction of Cr (Ⅵ) in aqueous solution after 8 h

the maximum photocatalytic reduction efficiency of Cr (Ⅵ) was 9.32％，48.73%，100％ and 100％ for PO43-

NO3-

Cl- and SO42-

respectively.Based on the research results

effectively keeping the acidity of solution and selecting a suitable acidic medium in the photocatalytic reduction of Cr (Ⅵ) process can further enhance the photocatalytic activities of sulfate modified titanium-bearing blast furnace slag photocatalysts.