A method of producing a copper-chitosan polymer material for adsorption of urea from a dialysis solution. A solid chitosan polymer material is immersed in a copper salt solution of a weak acid, such as copper acetate, for allowing the copper ions to complex with the chitosan polymer. The macroporous chitosan polymer membrane has a thickness of no more than about 200 &mu；&pgr；&iota； and has a pore size of between about 1 to 100 &mu；&pgr；&iota；, for example 20 to 50 &mu；&pgr；&iota；. Alternatively, solid chitosan fibers, solid chitosan particles or a chitosan gel bead can be complexed with copper acetate. The concentration of the copper acetate solution is above 50 mM whereby gel formation of the solid chitosan material is avoided during the complexation step.
