The presented work introduces the chemical modification of coal fly ash (FA) treated with NaOH and hexadecyltrimethylammonium bromide (HDTMABr) used as adsorbent for the removal of cadmium(II) ions and rhodamine B (RB) from aqueous solution. The FTIR spectrum shows the presence of organic and inorganic entities that are also seen on the XRD chart. The SEM analysis shows clearly the surface morphology and roughness of FA-HDTMABr. The effect of pH on adsorption equilibrium was studied. Maximum adsorption was found for pH values of 9. The Cd(II) ions and RB dye sorption is attributed to different mechanisms of the ion-exchange processes as well as to the adsorption. On the basis of reduced chi-square test (χ²/DoF) values obtained for both sorbates of the considered isotherms, the fitting degree follows the immediate sequence: Langmuir>Jovanović>Redlich-Peterson>Tóth>Freundl ich>generalized Langmiur-Freundlich>extended Jovanović>Halsey>Temkin>Dubinin-Radushkevich> Fumkin-Fowler-Guggenheim>Fowler-Guggenheim-Jovanović-Freundlich>Brunauer Emmett and Teller. The maximum monolayer adsorption capacity of the FA-HDTMABr was found to be 744 mg·g^-1 and 666 mg·g^-1 for Cd(II) and RB, respectively. The PFO, PSO, Elovich mass transfer, liquid film diffusion and intra-particle diffusion models were analysed. The PSO model (R² = 0.996) was slightly lower for Cd than those of the PFO model (R²<0.7), which is an indication that the PSO model was better than the PFO model. Purification water containing direct Cd and RB was made with 94% efficiency after 1 hour. We found that the chemical enhancement of FA from coal combustion by HDTMABr treatment yields an effective and economically feasible material for the treatment of basic dye and Cd(II) ions containing effluents.