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Leachability of elements from sub-bituminous coal fly ash from India
T Praharaj1, M A Powell, B R Hart
1Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur.
Environment International
|April 6, 2002
Summary
Ash pond leachate poses environmental risks. Serial batch leaching revealed that while some metals like Cd, Co, Cr, and Ni did not leach, As, Mn, and Mo exceeded safe drinking water limits.
Area of Science:
- Environmental Science
- Geochemistry
- Water Quality
Background:
- Ash pond leachate poses significant environmental risks due to soluble metal species.
- Understanding element behavior during leaching is crucial for assessing water contamination.
- Fly ash disposal requires careful management to prevent soil and water pollution.
Purpose of the Study:
- To investigate the leaching behavior of various elements from ash pond leachate.
- To assess the potential contamination of soil, surface, and groundwater.
- To compare leachate concentrations with established drinking water standards.
Main Methods:
- Serial batch leaching experiments were conducted simulating rainwater conditions.
- Leachates were analyzed for a comprehensive list of elements using inductively coupled plasma optical emission spectrometry (ICP-OES).
- Physical and mineralogical changes in ash samples before and after leaching were examined.
Main Results:
- Cadmium, cobalt, chromium, and nickel showed negligible leaching.
- Copper and lead concentrations were insignificant across different liquid to solid (L/S) ratios.
- Arsenic, manganese, and molybdenum concentrations exceeded World Health Organization (WHO) drinking water guidelines.
- Iron, manganese, and arsenic levels surpassed United States Environmental Protection Agency (USEPA) maximum allowable concentrations.
- Most elements leached in higher concentrations at lower L/S ratios, decreasing as L/S increased.
Conclusions:
- Leaching behavior is element-specific and influenced by the liquid to solid ratio.
- Ash pond leachate presents a risk of contaminating drinking water sources with specific heavy metals.
- While mineralogy remained unchanged, changes in specific surface area and morphology of post-leached fly ash were observed.
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