Submitted to: Water Environment Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2006
Publication Date: 11/14/2006
Citation: Fitzmorris, K.B., Lima, I.M., Marshall, W.E., Reimers, R.S. 2006. Anion and cation leaching or desorption from activated carbons from municipal sludge and poultry manure as effected by ph. Water Environment Research. 78(12):2324-2329. Interpretive Summary: In investigating the use of poultry waste and municipal sludge as sources for activated carbon, it was discovered that the carbons produce a significant amount of ash that contains metals. The metals are concentrated in the carbons and could potentially pose a problem during the use of the carbons for future adsorption and/or desorption of metals. The purpose of this study was to determine if the carbons would release these metals during application and cause contamination. We observed the adsorption/desorption of six metals (cadmium, copper, nickel, zinc, chromium, and lead) and two non-metals (arsenic and selenium) based on their importance as environmental pollutants. Our results show that the carbons under conditions normally found in water and wastewater do not release these metals. However, under highly acidic conditions, some metals are released such as copper and zinc, which indicates the carbons have the potential to be reused.
Technical Abstract: The conversion of municipal sludge and poultry manure to activated carbon results in a significant ash fraction that contains several different anions and cations. This is a cause for concern because the ash fraction could desorb from the carbon during application of the carbon and contaminate the medium to be remediated. The objectives of this study were 1) to determine whether select ions are released or leached from virgin carbon into the sorption medium at different pH values and 2) to quantify the desorption of select ions at different pH values after adsorption occurs in the virgin carbons. Activated carbon was placed in solutions of pH 1, 5 or 7 and the leaching of six cations (cadmium, chromium, copper, nickel, lead and zinc) and two anions (arsenate and selenate) was recorded. Considerable quantities of zinc and copper ion were removed at pH 1 from all carbon sources. However, amounts of zinc, copper and other ions leached at pH 5 and 7 were small or could not be detected. After ion adsorption at pH 5, desorption with 0.1 M HCl (pH 1) removed significant amounts of ions, but desorption in water at pH 7 showed little if any ion in solution. Our results indicate that leaching or desorption from carbons made from municipal sludge or poultry manure is pH dependent and occurs readily under highly acidic conditions but minimally under pH conditions usually seen in contaminated water or wastewater