Leaching of toxic metallic elements (Cu, Zn, As, Cd, and Pb) from two solid mine wastes was characterized under different drying treatments. During 14 batch decant-refill leaching steps, samples were intermittently dried four times in 40 °C oven or −20 °C freezer. For all leachates, the pH, pE, Fe2+/Fe3+, and SO42− were analyzed. The parameters of the two-site model (kfast, kslow, and ffast) and labile fractions (F1 + F2) were determined. High levels of toxic metallic elements were determined in waste samples; however, their leaching was limited, as evidenced by the magnitudes of F1 + F2, ffast, and kslow. Leachate solutions were acidic, at pH 3–4, and oxic, at 150 mV < Eh 300 < mV, thus having negligible Fe2+. Leachate concentrations of toxic metallic elements increased (4–58%) after drying at 40 °C and were strongly correlated (r2 = 0.780) with those of sulfate in liquid phase. The mass of element elution was in the order of 40 °C drying > −20 °C drying ≥ continuous wetting. Results indicate that the element leachability is increased through drying events and the leachate concentration is associated with the dissolution reaction of sulfur-bearing minerals. Frequent occurrence of prolonged droughts along with high temperatures over the mine waste disposal site, can enhance the leaching potential of toxic metallic elements.
Bibliographical noteFunding Information:
This study was supported in part by National Research Foundation of Korea (NRF) grant ( NRF-2017R1D1A1B04029194 ) and also in part supported by a Korea University Grant.
- Abandoned mine
- Labile fraction
- Metallic elements
- Mine leachate
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry
- Health, Toxicology and Mutagenesis