METHOD OF REMOVING PRINTING INK FROM WASTE PAPER BY FLOTATION DEINKING

摘要

Continuous flotation deinking of waste paper under alkaline conditions may not satisfactorily remove hydrophilic and water-soluble printing inks. The invention solves that problem by a two-stage flotation method. An alkaline flotation step is immediately followed by a flotation step in the neutral to weakly acid pH range, the pH value being lowered at the beginning of the second flotation step to a pH value in the range of from 5 to 7.5 using carbon dioxide.