An investigation was conducted to determine the ability of chemical treatment to reduce the leaching of metals from fly ash. A further objective was to determine the effect of cofiring refuse-derived fuels with coal on leachate composition. Samples of fly ash were treated with portland cement, chemically pure lime, and phosphoric acid and subjected to a column leaching process. The leachates were composited weekly and analyzed using X-ray fluorescence and atomic absorption spectrometry.
Portland cement or lime reduced the quantity of leached arsenic 40 to 80% from the control samples, whereas those samples fixed with phosphoric acid yielded 50 times more arsenic. Generally, the samples treated with portland cement showed the most uniform reduction in leachate concentrations.
Leachates from fly ash produced upon cofiring refuse-derived fuel with coal showed consistently higher concentrations of all elements except for calcium, selenium, and alkalinity.
Compaction and curing of the chemically treated ash samples showed little improvement in the ability to control the amount and types of metals appearing in leachates.