Intrinsic metal binding capacity of kraft lignins

The metal removal properties of kraft lignins were examined for a series of SW kraft pulps. The addition of purified kraft lignins to pulp fibers was shown to result in the removal of 20 to 40% of nonprocess elements, such as Mn, Mg, and Ca, in pulp. The effects of concentration and type and amount of kraft lignin applied were explored. These studies illustrate that structural differences in the kraft lignin affect the metal removal from pulp. Factors such as extent of delignification and cooking technology influence metal removal properties. In addition, we have demonstrated that a correlation exists between metal removal and the content of carboxylic acids and condensed phenolics in the kraft lignin applied.