The photocatalytic degradation of dyes(Acid Chrome Blue K(ACBK) and Alizarin Red(AR)) with strong complexation ability was investigated in the presence of metal ions under visible light irradiation.It was found that,at low dye-metal ratio,the photodegradation of ACBK was markedly inhibited by the addition of high oxidative potential Cu2+.However,at high dye-metal ratio,the presence of Cu2+ enhanced the photodegradation of ACBK.The negtive effect of Cu2+ on the photodegradation of AR was observed for all dye-metal ratios.The relative chemical inert Zn2+ tended to enhance the photodegradation of both anionic dyes.The mechanism underlying the different effect of Cu2+ was discussed from the different roles of surface-adsorbed and dye-coordinated Cu2+ in the photodegradation of dyes.
