Cl^－ and SO₄^2－ are the most common inorganic ions in dye polluted water. The effect of these ions on the photoelectrocatalytic degradation of the reactive brilliant K-2BP using TiO₂/Ti as anode is investigated. It is found that the concentration of the electro-lyte, the acidity of the solution and the use of mixed electrolytes alter the degradation process. When NaCl is used as the electrolyte, active chlorine is formed during the process, and is found to be responsible in com-bination with photo- and electro-effects for the degradation of dye; while Na₂SO₄ is used as electrolyte, two categories of reactions will occur. SO₄^2－ may trap HO• and h⁺, thus the efficiency of degradation is reduced. Under the conditions investigated, SO₄^2－ ion may also catalyze the formation of hydrogen peroxide, which is active for the degradation, and then the degradation is favored.

Key words: photoelectrocatalysis, reactive brilliant K-2BP, TiO₂/Ti electrode, electrolyte