The present paper investigates the sorption of antimony (V) on Fe-modified biomaterials (Fe-modified peat, shingles, moss, straw, canes, and sand) using batch tests. Synthesis and modification of biological matrix sorbents have been done. The Fourier transformation infrared (FT-IR) spectra, scanning electron microscopy (SEM), specific surface area, as well as organic substance content, and Fe2O3 analyses were used to characterize the obtained sorbents. Experiments of antimony (V) sorption have been performed. The experimental adsorption data were fitted by the Langmuir isotherm model and Freundlich isotherm model. Antimony sorption was investigated as a function of temperature, and thermodynamic parameters were calculated. The highest sorption capacity was observed for Fe-modified peat; it exceeded 40 mg/g at the initial Sb (V) concentration of 730 mg/L. Fe-modified peat can sorb up to 95% of Sb (V) at the initial concentration of 370 mg/L, and it decreases to 75% at the initial concentration of 730 mg/L. Fe-modified moss and Fe-modified shingles can also be used in severely polluted waters. The impact of temperature on the antimony (V) sorption capacity of Fe-modified peat was tested at four temperatures: 275 K, 283 K, 298 K, and 313 K, and the sorption capacity increased with an increase in temperature. The calculated thermodynamic parameters suggest that the sorption process is of a spontaneous nature and endothermic. The obtained results are in agreement with other studies, suggesting that the sorption process using different sorbents based on natural materials is spontaneous and endothermic, at the same time being greatly dependent on the materials used.