Differences in Leaching Characteristics of Mg and Ca from Various Biomass Components of Mallee Tree in Hot-Compressed Water

Abstract

In hot-compressed water (HCW), water-insoluble Mg and Ca become leachable from mallee wood, leaf, or bark. The extent of leaching of Mg and Ca varies from component to component in order of leaf > wood > bark for Mg and wood > leaf > bark for Ca. Such differences are due to two reasons: differences in the occurrence forms of Mg and Ca and differences in hemicellulose decomposition for different biomass components. For example, most water-insoluble Mg in wood and bark is ion-exchangeable, but only part of water-insoluble Mg in leaf is ion-exchangeable, with the rest being acid-soluble but not ion-exchangeable. Most water-insoluble Ca in wood is ion-exchangeable, but those in leaf and bark are acid-soluble but not ion-exchangeable. The results show that water-insoluble Mg or Ca in the ion-exchangeable form can be rapidly leached in HCW, but the leaching of water-insoluble Mg or Ca in the acid-soluble but not ion-exchangeable form is considerably slower as a result of the poor solubility of these species in ...