The presented work introduces a simple modification of coal fl y ash (FA) with 30% solution of H ₂0 ₂, used as a new efficient sorbent for the removal of organic dye crystal violet (CV) in the presence of Cu(II) ions in single- and bi-component systems Cu(II)-CV. FT-IR, TG, SEM-EDS, and XRD suggested that the mechanism of Cu(II) and CV sorption onto FA-H ₂O ₂ includes ion-exchange and surface adsorption process. Comparing the values of the reduced chi-square test (χ ²/DoF) and the determination coefficient R ² obtained for CV of the considered isotherms, the fitting degree follows the sequence: Jovanović > Langmuir > Elovich > Freundlich > Redlich-Peterson (R-P) > Tóth > Halsey > BET. Sorption of Cu(II) ions in a single system by means of FA-H ₂O ₂ was well fi tted by the Langmuir and R-P model. The studies of equilibrium in a bi-component system by means of extended Langmuir (EL), extended Langmuir-Freundlich (ELF), and Jain-Snoeyink (JS) models were analysed. The estimation of parameters of sorption isotherms in a bi-component system Cu(II)-CV has shown that the best of fi t calculated values of experimental data for both sorbates have been the EL model and the JS model, but only in the case of a CV dye. The sorption kinetic of Cu(II) and CV onto FA-H ₂O ₂ was discussed by means of the PFO, PSO, and intra-particle diff usion models.