In the present work, a low-cost sorbent prepared from mixed local conifer sawdust (SW) and fly ash (FA) provided by a Romanian power plant was developed. On the basis of the preliminary studies, both materials were qualified as suitable sorbents for the removal of copper ions; however, the sorption capacity and material structures of the SW is influenced by the FA. Therefore, a sorbent based on SW–FA mixture is proposed in this study for the removal of copper ions to improve the efficiency of the SW alone. The sorption capacity of the novel sorbent toward Cu(II) ion removal from aqueous solution has been investigated by employing the regression modeling techniques. In order to describe the sorption equilibrium, the obtained data were fitted using the classical isotherm models. In addition, the experimental design and response surface methodology have been applied for modeling and optimization of the Cu(II) removal process. The operational parameters used in the experimental design were as follows: the initial copper concentration, pH of initial solution and sorbent dose. The maximum removal efficiency of Cu(II) was 79.56 %, which was experimentally validated.