Removal of metal ions from wood chips during acidic leaching 1: Comparison between Scandinavian softwood, birch and eucalyptus

Artikel i vetenskaplig tidskrift, 2006

Acidic leaching of Scandinavian softwood, birch and eucalyptus has been studied, for the purpose of removing metal ions from the wood. Equilibrium experiments with wood powders were conducted to study the influence of pH. An increased release of metal ions was found, as expected, when the pH was lowered. For one sample of eucalyptus, the release of calcium accelerated when the pH was lowered to below 3, which led to the conclusion that a salt of low solubility could be present. Further investigations showed a high concentration of oxalate in this sample, which is likely to be an explanation for the accelerated release. Industrial cut wood chips, from Scandinavian softwood, birch and eucalyptus, were leached at different temperatures to study their leaching behavior. Birch and softwood were shown to have the same general leaching pattern for calcium and potassium. Eucalyptus showed the same leaching trend for potassium, but it was harder to remove calcium from eucalyptus than from softwood and birch. In the case of eucalyptus chips, which had a relatively high content of chloride (480 mg/kg wood), extensive removal of chloride was noted.