The adsorption mechanisms of copper (II), cadmium (II) and chromium (III) on the bark of Ezomatsu (Picea jezoensis CARR.) and on the inner or outer bark of Benimatsu (Pinus koraiensis SIEB. et ZUCC.) were investigated. The unextracted bark and the bark extracted with cold water, alcohol and/or 1% sodium hydroxide aqueous solution were shaken with 100ppm heavy metal aqueous solution adjusted to pH 6.0-6.5 at 30℃, for 24 hours. The relative contribution of chemical adsorption and physical adsorption on the bark-heavy metal system was synthetically discussed from the experimental data of amount of adsorbed heavy metal, heat of adsorption and amount of extractives.
As the results, it was recognized that the adsorption behavior was characterized by the combination of bark and heavy metal. It was assumed that physical adsorption contributes dominantly as compared to chemical adsorption in the adsorption of copper (II) on barks, while the adsorption of chromium (III) is mainly dominated by chemical adsorption, and the adsorption mechanism of cadmium (II) is intermediate between that of copper (II) and chromium (III).
Estimating the relative contribution of chemical and physical adsorption on each bark, it was also elucidated that the adsorption of heavy metal on Ezomatsu bark is primary dominated by physical adsorption, and that on the inner bark of Benimatsu is mainly dominated by chemical adsorption.
On the adsorption of heavy metal on barks, it was seemed that the extractives contents of barks are the main factor which dominates the adsorption behavior.