Humic substances removal by activated carbon

Humic substances are a major concern to the water treatment industry because they can cause odor and color problems and are potentially toxic and/or cancinogenic. A commercial humic acid and fulvic acid extracted from peat were used to evaluate the removal or humic substances by various activated carbons. Different analytical methods were investigated to measure the concentration of humic substances and their chloroform formation potential. Total organic carbon measurement and ultraviolet/visible absorbance correlate well with the chloroform formation potential of humic substances. Pore volumes of activated carbon in pores between 100 and 500 Å radius were correlated with adsorption capacity. A decrease of pH in solution, lower molecular weight fractions of humic substances, smaller carbon particles, and presence of soluble alum were found to increase the carbon adsorption. Chemical pretreatment with alum increased the adsorption capacity of carbon almost threefold. This increase of adsorption capacity is probably because of the removal of weakly- or non-adsorbable humic substances by alum coagulation. The presence of soluble alum in the solution also enhances the adsorbability of humic substances. The application of a developed mathematical model to predict the performance of the carbon bed for the adsorption of humic substances was successful. Model parameter estimation techniques and model verification were evaluated and the applicability of the model was verified. In general, this model is sensitive to values of adsorption capacity of activated carbon and the surface diffusion coefficient was also correlated with the adsorption capacity. The higher the adsorption capacity, the lower the diffusion coefficient. Based on the model predictions, the empty bed contact time of the carbon bed and the influent concentrations were the two most important factors in designing a carbon bed for humic substances removal.U.S. Department of the InteriorU.S. Geological SurveyOpe