The main component of wood is lignin. Lignin is a polymer compound in which a hydroxyl group or a methoxy group is bonded to the benzene ring, and its structure is very complicated. However, lignin has many parts that form * complexes with metal ions, such as phenol and carboxyl groups.
* Complex = A combination of other ions, atoms, molecules, and atomic groups with atoms and ions of metal elements and metal-like elements as the center.
However, the amount of heavy metal ions such as copper and silver adsorbed in the state as it is is insignificant. So we mixed wood chips and cement. When lignin contained in wood chips is placed in an alkaline environment, hydrogen ions dissociate from phenolic hydroxyl groups and adsorb a large amount of heavy metal ions.
Copper ions and silver ions are adsorbed on this. This bond is stable and will not flow.
In this way, cement, wood chips, and copper ions and silver ions work comprehensively to exert various functions.