Characterization and activated carbon adsorption of several humic substances

A commercially supplied humic acid, extracts of a Michigan Finch soil, and extracts of leaves from a hardwood forest were characterized by molecular size fractionation, functional group analysis, and haloform formation potential. The haloform formation potential was dependent on the source of the material; differences could not be correlated with the amounts of oxygen-containing functional groups in each substance. A bituminous-base activated carbon adsorbed each humic substance with the adsorption capacity at seven days being source-dependent. The extent of adsorption of humic material from various sources was inversely related to the number of carboxyl groups per unit weight of the substance. The lower molecular weight species of a given humic or fulvic acid was more adsorbable, presumably because more surface area was accessible to these species. Soil fulvic acid adsorption increased with decreasing solution pH and increasing phosphate buffer concentration. Due to the variability of haloform formation potential and adsorbability of humic substances from different sources, treatment performance to remove these materials should be evaluated using the specific water to be treated.