Heavy metals are highly toxic and non-biodegradable pollutants that have a negative impact on living organisms due to ingress into water and soil. Therefore, the development of industry and the ever-increasing anthropogenic load determine the urgency of finding novel materials and technologies effective for solving this problem. Synthetic and natural adsorbents are widely used for heavy metal ions removal from aqueous media and for soils remediation. Metal phosphates are characterized by an increased affinity for polyvalent metal ions, while the attention of researchers is directed to the development of methods for the synthesis of these materials using available natural raw materials. This work is devoted to the study of the adsorption properties of mixed Zr-Ca-Mg phosphates to Co2+ ions. The choice of the research object was due to the simplicity of the obtaining method and the use of natural dolomite as a common and widespread raw material. In addition, these materials have shown high efficiency in 137Cs, 90Sr and 60Co radionuclides removal from aqueous solutions of complex radionuclide composition, which makes it possible to significantly expand the adsorbent application. Zr-Ca-Mg phosphates were obtained by heterogeneous interaction of phosphatized dolomite Ca0.7Mg0.3HPO4∙2H2O with 2.0 wt.% aqueous solution of zirconyl nitrate ZrO(NO3)2 with a molar ratio (Ca + Mg) / Zr of 1/0.36 (Zr-1) and 1/1.1 (Zr-2). Adsorption of Co2+ ions was performed in batch experiment from Co(NO3)2 aqueous solutions (Cinitial 50-3500 mg/L, V/m 250 mL/g, contact time 24 h). The initial and equilibrium Co2+ ions concentrations were determined by atomic emission spectrometry. To determine the adsorption mechanism, experimental data were calculated using Langmuir, Freundlich, Sips and Redlich-Peterson adsorption models. The correspondence of the experimental data to the specified models was determined by the approximation coefficient and the value of the experimental error. The adsorption isotherms of Co2+ ions by Zr-Ca-Mg complex phosphates had a pronounced vertical section at the initial stage, which indicated a high affinity of the adsorbent to the adsorbate and allows them to be classified as H-type according to the Giles classification. The maximum Zr-1 and Zr-2 adsorption capacity from 0.05 M Co(NO3)2 solution was 253 and 156 mg/g, respectively. The adsorption isotherms of Co2+ ions by Zr-1 and Zr-2 samples were correctly described by the Sips equation, which indicates the adsorption centers heterogeneity of the composite adsorbents. Thus, the obtained results indicated the high efficiency of the studied Zr-Ca-Mg phosphates as Co2+ ions adsorbents, which together with the previously obtained data on 60Co radionuclides adsorption, allows them to be used for effective treatment of wastewater and liquid radioactive waste. Acknowledgements: This work was financially supported by Belarusian Republican Found for Fundamental Research (Grant No. X20MC-022).