Xylanase-Assisted Metal Ion Removal from Kraft Pulps, 1996 International Pulp Bleaching Conference Proceedings

Leon Magdzinski

Repap Technologies

Xylanase assisted in the removal of metals detrimental to TCF bleaching processes at pH 2.5-5. The action of xylanase was similar to that of EDTA. Kraft softwood pulp kappa 25.5 containing 21ppm Fe, and 187 ppm Mn was treated with xylanase No. 1 enzyme at pH 3.5 for 2h then washed to give a pulp containing 6 ppm Fe, and 48 ppm Mn. Treating the starting pulp with 0.05 % EDTA at pH 5 and washing gave a pulp with 22 ppm Fe, and 65 ppm Mn. Washing at pH 3.5 decreased the starting pulp metals to 17 ppm Fe, 102 ppm Mn. Xylanase No.2 enzyme treatment at pH 6.5, followed by washing at pH 3.5 gave a pulp with 14 ppm Fe and 55 ppm Mn versus 15 ppm Fe and 145 ppm Mn at pH 6.5. Bleaching of the starting pulp, the EDTA treated pulp, and the No. 1 enzyme pulp with a EopDEpD sequence (3.1% Cl02 and 2.0%H202) produced bleached pulps with the following respective characteristics: 86.2, 86.8, 88.3 % ISO; 12.5, 13.6, 16.1 cps viscosity, and breaking length X tear index of 84, 89, 102 at 400CSF.