Abstract: Effects of SO^2-₄,HCO^-₃ and Cl^- in mine water on performance of photocatalytic degradation of mine water COD_Cr with TiO₂. After the anions in mine water were fully filtered with anion resin, simulant mine water samples with eath of Na₂SO₄,NaHCO₃and NaCl and composites between the 3 salts were respectively prepared, and photocatalytically degradated COD_Cr in mine water with homemade TiO₂ under ultraviolet light irradiation. When they existed singly, all the three kinds of anions can decline the COD_Cr photocatalytic degradation rate in the order of HCO^-₃>SO^2-₄>Cl^-,4.45 mmol/L Cl^- accelerating COD_Crdegradation rate a little. When composites every two of the three kinds of anions, HCO^-₃ and SO^2-₄, HCO^-₃ and Cl^-,as HCO^-₃ concentration is low, common effects of HCO^-₃, SO^2-₄ or Cl^- lower COD_Cr degradation rate, while HCO^-₃ plays a major role; as HCO^-₃ is in high concentration, HCO^-₃ achieves absolute role. In composite experiment of SO^2-₄ and Cl^-,Cl^- concentration is 4.45 mmol/L, promoting COD_Cr degradation rate slightly in the range of concentrations of SO^2-₄；Cl^- is higher than this concentration, Cl^- and SO^2-₄ compositions have the synergy effect on lowering COD_Cr degradation rate, and are lower than that they exist individually.

Key words: coal mine water, TiO₂, degradation rate, COD_Cr  