Bleaching of commercial pulps with H20 2 catalyzed by heteropolyacids

Several studies have taken placc in order to find an alternative bleaching process which replaces the chlorinated compounds with environmentally friendly agents as well as recycles the effluents, instead of discharging them. In this study we employed hydrogen peroxide and Keggin-type heteropolyacids for the selective removal of lignin from the pulp. We used heteropolyacids containing W, Mo and MolY, in aqueous solution, to bleach different commercial pulps with hydrogen peroxide. Kraft pulp, water, heteropolyacid (5 mmoll I) and H,O, (I % w/w) were combined to obtain a final pulp consistency of 3%. The mixture was heated in a glass reactor to 60, SO or JOO°C for 2 or 4 h. The best experiment furnished a pulp with a Kappa number of 3.2 and a viscosity of 17.1 cP, using H,PMo1,O.J1I and 1% H20, (w/w) at 60°C for 4 h.