Abstract
Precipitates induced by the pore-scale mixing of iron sulfate solutions with simulated groundwater were investigated using a microfluidic pore model to assess the environmental impacts of the infiltration of acid mine drainage into a shallow aquifer. This model was employed to visualize the formation of precipitates in a porous network and to evaluate their physicochemical influences on pore flow. Four types of groundwater (Na–HCO3, Na–SO4, Na–Cl, and Ca–Cl) were evaluated, and precipitation rates were calculated by processing images of precipitates in the pores captured via microscopy. The results showed that all groundwater types formed a yellow-brownish precipitate at the interface of the iron solution and simulated groundwater flow. Microscopic X-ray analyses demonstrated that precipitate morphology varied with groundwater type. Faster precipitation was observed in the following order by groundwater type: Na–HCO3 > Na–Cl > Na–SO4 > Ca–Cl, which was attributed to the different stability constants of the major anions in each simulated groundwater with Fe ions. Chemical equilibrium models suggested that precipitates were Fe minerals, with FeOOH as the predominant form consistent with the results of X-ray photoelectron spectrometry. The presence of FeOOH implies that precipitates may serve as an effective sorption barrier against some nutrients and heavy metals for the underlying groundwater. However, dye-flow experiments suggested that the precipitates may clog aquifer pores, thereby altering hydrogeological properties in the aquifer.
Original language | English (US) |
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Article number | 129857 |
Journal | Chemosphere |
Volume | 271 |
DOIs | |
State | Published - May 2021 |
Externally published | Yes |
Bibliographical note
Funding Information:We thank Sohee Kim and Heekyung Kang at KIST for the SEM and XPS analysis, respectively. This work was supported by the Korea Environment Industry & Technology Institute (KEITI) through the Subsurface Environment Management (SEM) Project ( 2018002440006 ) funded by the Korea Ministry of Environment (MOE), and by the National Research Foundation of Korea (NRF) through the ‘Climate Change Impact Minimizing Technology’ Program funded by the Korean Ministry of Science and ICT (MSIT) ( 2020M3H5A1080712 ). The authors also acknowledge the support from the Future Research Program ( 2E30510 ) funded by the Korea Institute of Science and Technology (KIST).
Publisher Copyright:
© 2021 Elsevier Ltd
Keywords
- Acid mine drainage
- Groundwater contamination
- Iron precipitate
- Microfluidic pore model
- Pore clogging
PubMed: MeSH publication types
- Journal Article