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EFFECTS OF pH, ORP, AND CONDUCTIVITY ON LEACHING OF TRACE METALS FROM FLY ASH

By George Kazonich

Abstract

Leaching of metals from coal utilization by-products (CUB) is being studied to assess the potential for environmental damage. Samples contained in fixed-bed columns were leached with five lixiviants. The lixiviants simulated environmental liquids and varied from acidic to alkaline (pH 1 to pH 11). The leachates were analyzed for major and trace metals. Trace metals that formed cations were leached by acidic lixiviants although, in most cases, the total amount leached was small. The concentrations of metals were low initially, increased rapidly after the alkalinity of the CUB was depleted, then dropped rapidly after a maximum was reached. For normal Class F fly ash samples, the maximum concentrations of acid soluble trace metals in the leachate were typically less than 10 mg/L. A Class F fly ash produced during an SCR test produced leachates with much higher concentrations of metals. ORP appeared to be as good an indicator of leaching progress as pH while conductivity was a less indicative but possibly adequate monitor

Year: 2010
OAI identifier: oai:CiteSeerX.psu:10.1.1.162.3056
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