Removal of Manganese From Pulp Fibers with MgSO4 in a Displacement System, 1999 Pulping Conference Proceedings

Z. Li

Irving Paper Inc.

A.R.P. van Heiningen

Department of Chemical Engineering

University of Maine

Y. Ni

Limerick Pulp and Paper Centre

University of New Brunswick

Removal of manganese from pulp fibers is usually achieved in a chelation stage with DTPA or EDTA. It can also be carried out in a treatment with magnesium sulfate via the so-called ion exchange technique. In such a process, manganese, the bad metal ion present in pulp fibers, is replaced by magnesium, a good metal ion. If this ion exchange technique is conducted in a stirred tank reactor, a very high dosage of the good metal ions is required to decrease the manganese content to a reasonably low level. In this paper we will report that when the ion exchange technique is conducted in a displacement system, the magnesium sulfate charge can be significantly decreased to have a good chelation result. For example, with a magnesium sulfate charge of 1% , a residual manganese content of about 5 ppm can be reached from a pulp containing 150 ppm manganese. The manganese removal in such a process is similar to that during a conventional chelation stage with DTPA or EDTA. The bleaching responses in a subsequent peroxide stage of chelated pulps were compared.