A process for making defibered pulp material comprising the steps of treating fibrous ligno-cellulosic material with aqueous nitric acid having an HNO3 concentration of about 0.15 to 9.0 wt.% and containing at least one aluminum compound in an amount of at least 0.01 parts by weight of aluminum ions per each 10 parts by weight of HNO3 (10,17), so as to nitrate ligneous component of said material; and thereafter defibering (15,21) directly, or treating the nitrated ligno-cellulosic material with alkali (13, 19) to seperate the ligneous component from the cellulosic pulp, and, optionally, recombining a part or all of the ligneous component with the cellulosic pulp.
