Removal of Humic Substances and Their Metal Complexes by Adsorption

The adsorption of organic polyelectrolytes (humic and fulvic acids) by bone char was characterized. The bone char was found to be a useful adsorbent for humic substances compared with an activated carbon. The present method was also successfully applied to the removal of metal-humic material complexes. The molecular weight distributions of the humic substances remaining in solution after adsorption with the bone char were measured with size-exclusion chromatography. A comparison of molecular weight distributions demonstrated conclusively that large molecular-weight components were adsorbed preferentially. Furthermore, the surface conditions of the adsorbent were observed before and after adsorption by a scanning electron microscope. From the observation, it was found that the adsorption ability of the adsorbent was closely related to its pore size. The calculated heats of adsorption were over 50 kJ mol^-1, which was evaluated from the Clapeyron-Clausius equation. Therefore, the adsorption type appeared to be chemical adsorption.