The effect of chemical modification on the sorption properties of cellulose with respect to Cu(II) ions has been studied. Modification was carried out through the oxidation of cellulose with sodium metaperiodate with the formation of dialdehyde cellulose, its subsequent interaction with 4-aminobenzoic acid and conversion into a derivative capable of chelating heavy metal ions. Analysis of the obtained sample with grafted carboxyl groups is carried out, and a conclusion is drawn about the influence of the structure of sorption centers on the efficiency of sorption of heavy metal ions. The kinetics and equilibrium of sorption of Cu(II) ions by the modified sorbent in comparison with the native sample have been investigated. Sorption kinetic curves were processed within the framework of the pseudofirst and -second order kinetic models. The results of the kinetic experiment are described most correctly within the framework of the pseudosecond order model. The experimental isotherms of sorption of Cu(II) ions from aqueous solutions by native and modified cellulose are well described by the Langmuir equation. The processing of isotherms in the linear form of the equation made it possible to determine the values of the limiting sorption of Cu(II) ions by the studied cellulose samples. The modified sorbent surpasses native cellulose in sorption capacity by about 2.7 times, which is due to the presence of new sorption centers in its structure. Studies performed by scanning electron microscopy indicate a change in the surface structure of the modified sorption material in comparison with the original one. IR spectra indicate the appearance in cellulose in the process of modification carboxyl groups.