Water quality implications of the neutralization of acid mine drainage with coal fly ash from India and the United States
Abstract
Subsurface coal mining often induces the formation of acid mine drainage (AMD) in
active and abandoned coal mines while coal combustion generates coal combustion residuals
(CCR), including fly ash (FA), with elevated levels of toxic metals. Decades of AMD
and CCR production have caused major environmental and human health impacts. Given
the typically elevated level of oxides in FA, previous studies have examined its potential
to neutralize AMD and remove the associated metals. While the neutralization of AMD
through reaction with FA has been demonstrated to successfully remove cationic metals,
the fate of oxyanion forming elements are less well studied and is the focus of this
study. Here we conducted 49 different experiments in which simulated AMD solutions
were interacted with representative U.S. (n = 7) and Indian (n = 6) FA samples through
controlled liquid to solid ratios in short-term (24 h) and long-term (up to 5 weeks)
lab-scale experiments. We show that Class-F FA, originating from Gondwana and Northeastern
Tertiary coals in India, has limited neutralization capacity, while Class-C FA, with
high CaO and MgO contents from Powder River coals in the U.S. has the greatest AMD
neutralization capacity among the studied fly ashes. The neutralization experiments
show that AMD-FA reactions cause the removal of cationic elements (i.e., Fe, Mn, and
Al) from solution, while at the same time, leaching oxyanion forming elements (i.e.,
As, Se, Mo, Cr, B, Tl, and Sb) from the FA, increasing the potential environmental
risks from the treated leachates. The magnitude of mobilization of these elements
depends on their concentrations in the FA and the pH conditions. We show that using
FA from the Appalachian and Illinois coals efficiently neutralizes AMD, but also results
in secondary contamination of the treated effluents with oxyanion forming elements
to levels exceeding drinking water and ecological standards, which could contaminate
the ambient environment, whereas neuralization with Powder River Basin Class-C FA
induces only limited contamination.
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https://hdl.handle.net/10161/26629Published Version (Please cite this version)
10.1016/j.fuel.2022.125675Publication Info
Weinberg, R; Coyte, R; Wang, Z; Das, D; & Vengosh, A (2022). Water quality implications of the neutralization of acid mine drainage with coal fly
ash from India and the United States. Fuel, 330. pp. 125675-125675. 10.1016/j.fuel.2022.125675. Retrieved from https://hdl.handle.net/10161/26629.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Avner Vengosh
Nicholas Distinguished Professor of Environmental Quality
Avner Vengosh is a Duke University Distinguished Professor of Environmental Quality
at the Nicholas School of the Environment. Professor Vengosh and his team have studied
the energy-water nexus, conducting pioneer research on the impact of hydraulic fracturing
and coal ash disposal on the quantity and quality of water resources in the U.S. and
China. He has also investigated the sources and mechanisms of water contamination
in numerous countries across the globe, including salinity and
Zhen Wang
Student
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