HR: 1340h
AN: H53A-1226    [Abstracts]
TI: Comparative adsorption of arsenic, boron, chromium, molybdenum and selenium on fresh and weathered fly ash.
AU: * Bhattacharyya, S
EM: bhatt001@bama.ua.edu
AF: Dept. of Geological Sciences, University of Alabama, Tuscaloosa, Al 35487-0338, 202 Bevill Building, Tuscaloosa, Al 35487 United States
AU: Donahoe, R J
EM: rdonahoe@wgs.geo.ua.edu
AF: Dept. of Geological Sciences, University of Alabama, Tuscaloosa, Al 35487-0338, 202 Bevill Building, Tuscaloosa, Al 35487 United States
AU: Graham, E Y
EM: bgraham@wgs.geo.ua.edu
AF: Dept. of Geological Sciences, University of Alabama, Tuscaloosa, Al 35487-0338, 202 Bevill Building, Tuscaloosa, Al 35487 United States
AU: Patel, D V
EM: dvpatel@southernco.com
AF: Southern Company Services Inc., Southern Company Services Inc. Inverness Center Parkway, Birmingham, Al 35242 United States
AB: Coal-fired electric power plants in the US generated over 130 million tons of fly ash and other combustion waste materials last year. While approximately 35% of the produced coal combustion by-products (CCBs) are recycled for beneficial use, the majority of the waste is impounded in lagoons and landfills located throughout the country. The EPA is currently re-evaluating these disposal facilities for regulation under Subtitle D. The objective of this study is to determine and compare the adsorption capacities of fresh and weathered fly ash for the toxic metals arsenic, boron, chromium, molybdenum, and selenium in order to evaluate the long-term mobility of these metals in the ash disposal environment. Two power plant sites were selected for study, one producing acidic ash and the other alkaline ash. Weathered ash samples were collected at each site from cores drilled from the surface through the bottom of ponds that have been closed for more than 35 years. Fresh fly ash was obtained directly from the power plants. Batch experiments were performed to study the competitive adsorption of As, B, Cr, Mo and Se on fresh and weathered ash materials. Experiments performed at pH values of 3, 4, 6, 8 and 10, using initial metal concentrations of 5 mg/L, show similar adsorption behavior for both ash compositions. The metal selectivity sequence for fresh fly ash is As >> Mo > Cr ~ Se ~ B. Maximum arsenic adsorption on fresh fly ash occurs at pH = 6 with almost 100% removal, while maximum arsenic adsorption on weathered ash takes place at pH = 3. Maximum adsorption of B, Cr, Mo and Se occurs at pH = 3 for both fresh and weathered ash. The experiments indicate that the adsorption capacity of fly ash for the metals of interest is reduced by weathering. Experiments are currently underway to compare the adsorption capacity of fresh and weathered fly ash for varying initial metal concentrations, ionic strength and solid/liquid ratio.
DE: 1899 General or miscellaneous
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting