The paper looks into likelihood in the membrane purification of the water contaminated by Co(II)-ions. Both the ceramic and polymeric membrane modified by the different additives have been used with this end in view. An application of the ceramic membranes under study is shown to be more preferable at the stage of water pretreatment. In case when the OPAM polymeric membrane makes use of, as the high degree of water purification as 92.8% is reached. An addition of the clay minerals into the system subjected to separation results in an essential increase of the water purification degree (up to 98.2%). The water state in the dynamic membranes has been studied by the differential-scanning calorimetry method. These membranes were formed by the different clay minerals to clear up both contribution and role of the inorganic additives in the membrane purification of sewage from the Co(Il)-ions.