The reaction of lignin with ammonium persulphate solution in NH4OH, in which polymeric N-containing derivatives are formed via oxidative coupling, has been discovered and investigated. A method for isolation of lignin from kraft black liquors with persulphate is proposed. Various aminolignins were synthesised by the reactions of lignins with aliphatic amines and their epoxyderivatives. Diethylaminooxypropxylignin has shown a high and specific bile acid absorptivity, and a novel medical preparation “Deapolin” has been developed. Aminolignins show a high absorptivity also toward heavy metal ions.