Three experimental series were carried out. In the first series, a molar ratio H₂O₂: 4-chlorophenol of 25:1, previously established as optimum for degradation, was used and 4-chlorophenol concentration was kept constant at 100 mg L^-1, while methyl green was varied between 25 and 100 mg L^-1. Results are shown in Figure 1, where it can be seen that the variation of dye concentration does not have an influence on the 4-chlorophenol degradation. Both the chlorophenol and the dye are completely removed in all cases.