Interaction of trace elements in acid mine drainage solution with humic acid

Area of Science:

• Environmental Science
• Geochemistry
• Analytical Chemistry

Background:

• Coal mining tailings can release significant metal ions.
• Acid mine drainage (AMD) is characterized by low pH and high sulfate concentrations.
• Natural organic matter, like humic acid (HA), plays a role in metal ion transport.

Purpose of the Study:

• To investigate metal ion release and interaction with humic acid from coal mining tailings.
• To understand the effect of dilution on metal-HA complex formation and colloid size.
• To characterize the composition of leachates and their interaction with natural organic matter.

Main Methods:

• Leaching tests using simulated rainwater and humic acid solutions.
• Asymmetric flow field-flow fractionation (AsFlFFF) coupled with UV/Vis and ICP-MS detection.
• Filtration and size analysis to observe colloid aggregate formation.

Main Results:

• Leachates showed low pH and high sulfate, characteristic of AMD.
• Metal-HA complexes were larger than native HA, indicating metal-induced agglomeration.
• Increasing metal-to-HA ratios led to larger HA entities and precipitation of Fe and Al at high ratios.
• In diluted solutions, HA acted as a carrier for metal ion mobilization.

Conclusions:

• Coal mining tailings are a source of metal pollution, contributing to AMD.
• Humic acid significantly influences metal ion behavior, promoting aggregation and mobilization.
• Understanding these interactions is crucial for managing environmental contamination from mining sites.