Adsorption of humic substances onto β-FeOOH and its chemical regeneration

Removing humic substances is a challenge for process engineering in drinking water treatment. Various processes have been developed in the past. However, due to problems in efficiency, waste disposal or high operating costs, the search for new solutions still persists. In this investigation we tested a new sorbent, a highly active granulated iron hydroxide with the beta-FeOOH modification, regarding its adsorption capacity and regenerability. Three Fulvic acids were used differing in molecular weight distribution and calcium content. Iron hydroxide showed high adsorption capacities for each of these fulvic acids. The dependency of adsorption on pH was comparatively small, whereas calcium improved DOC removal especially at pH-values higher than 6. Larger fulvic acid molecules were preferably adsorbed. Calcium free sodium hydroxide solution allowed complete regeneration. In a pilot plant study kinetic restrictions were obvious due to pore exclusion of high molecular weight substances. However the good results concerning adsorption capacity and regenerability encourage us to enlarge the pore sizes of beta-FeOOH granules. (C) 1999 Published by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved.