The technology of obtaining active carbon enriched in nitrogen from brown coal is described. The effect of ammoxidation by a mixture of ammonia and air at the ratio 1:3 at 300 and 350 degrees C, at each stage of the active carbon production has been tested. The amount of nitrogen introduced into the active carbon has been proved to depend on the stage at which ammoxidation was performed. Carbonisation and activation with steam of the samples enriched in nitrogen have been found to lead to a significant decrease in its content and to cause an increase in the stability of the nitrogen groups. The ammoxidation of the active carbon has decreased their surface area, while the ammoxidation and high temperature of activation favour the formation of surface oxide groups of basic character. (C) 2006 Elsevier B.V. All rights reserved.