Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2002
Publication Date: 10/30/2002
Citation: Ng, C., Losso, J.N., Marshall, W.E., Rao, R.M. 2002. Freundlich adsorption isotherms of agricultural by-product-based powdered activated carbons in a geosmin-water system. Bioresource Technology. 85(2):131-135. Interpretive Summary: Geosmin is a bacterial metabolite and is one of the substances commonly cited as responsible for the musty and earthy taste and odor in drinking water worldwide. Geosmin is also responsible for off-flavor in pond raised catfish and renders the fish inedible and unmarketable. Adsorption of geosmin with activated carbon is one possible method for reducing the amount of this unwanted chemical to below the human threshold of human taste and smell. In this study, a mathematical model was used to determine whether activated carbons made from the by-products pecan shells and sugarcane bagasse could reduce the concentration of geosmin to below the taste and smell threshold. The model determined that pecan shell-based carbons were particularly effective in this regard and were even more effective than a commercial carbon used for comparison. Therefore, by-product-based carbons, especially from pecan shells, may be utilized as a cheaper alternative to carbons currently available for geosmin remediation in catfish ponds and drinking water purification.
Technical Abstract: The present study was designed to model the adsorption of geosmin from water under laboratory conditions using the Freundlich isotherm model. This model was used to compare the efficiency of sugarcane bagasse and pecan shell-based granular activated carbon (GAC) to the efficiency of a coal-based commercial activated carbon (Calgon Filtrasorb 400). When data was generated from Freundlich isotherms, Calgon Filtrasorb 400 had greater geosmin adsorption at all geosmin concentrations studied than the laboratory produced steam-activated pecan shell carbon, steam-activated bagasse carbon, and the carbon dioxide-activated pecan shell carbon. At geosmin concentrations less than 0.07 micrograms/L for the phosphoric acid-activated pecan shell carbon and below 0.08 micrograms/L for a commercially produced steam-activated pecan shell carbon obtained from Scientific Carbons, these two carbons had a higher calculated geosmin adsorption than Filtrasorb 400. While the commercial carbon was more efficient than some laboratory prepared carbons at most geosmin concentrations, the results indicate that when the amount of geosmin was below the threshold level of human taste (about 0.10 micrograms/L), the phosphoric acid-activated pecan shell carbon and the Scientific Carbons sample were more efficient than Filtrasorb 400 at geosmin removal.