© 2020 Elsevier B.V.Radioactive cesium ion (Cs-137) removal from wastewater was investigated by novel composite adsorbents, chitosan-bone powder (CS-KT) and chitosan-bone powder-iron oxide (CS-KT-M) at 25 and 50 °C. The characterization of adsorbents was performed by Fourier-Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Brunauer-Emmett-Teller and Barrett-Joyner-Hallenda (BET-BJH), and Atomic Force Microscopy (AFM) analyses. While BET surface areas of CS-KT and CS-KT-M adsorbents were found to be 131.5 and 144.9 m2/g, respectively, average pore size and pore volume values were 4.69 nm/0.154 cm3/g and 7.49 nm/0.271 cm3/g, respectively. Amongst Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) models, Langmuir model fits well for Cs+ ion sorption by these adsorbents. The maximum adsorption capacity obtained from Langmuir adsorption isotherm was 0.98 × 10−4 mol/g at 25 °C, and 1.16 × 10−4 mol/g at 50 °C for CS-KT; it was found to be 1.79 × 10−4 mol/g at 25 °C and 2.24 × 10−4 mol/g at 50 °C for CS-KT-M. FT-IR analyses showed that Cs+ sorption occurs by its interaction with CO32-, PO43- and -NH2 groups. The average adsorption energy “E” was calculated as ca.11 kJ/mol from D-R adsorption isotherm. The adsorption kinetics was interpreted well by pseudo-second order model.