This granular material consists of a granular porous support bearing negative or positive charges, coated on its surface with a first layer of impregnation with a hydrophilic polymer bearing charges opposite to those of the support, the quantity of said charges present on said polymer being substantially equal to that of the charges present at the surface of the support; and another layer, bound to the first by irreversible chemical coupling, of another hydrophilic polymer which is functional, namely bearing groups endowing said functional hydrophilic polymer with a specific but reversible affinity for at least one biological substance. Among the applications of this material, there are mentioned the separation and purification of antithrombin III and coagulation factors (factors II, VII, VIII, IX, X), and separation of activated coagulation factors (activated factor II, activated factor IX, activated factor X) in solutions containing said non-activated factors.