Search

The release of potentially toxic elements (PTEs) from abandoned mining waste (AMW) is generally assessed with leaching tests. The United States, Mexico, and Spain's geological surveys respectively use leaching tests USGS FLT, NOM-141-SEMARNAT-2003, and EN-12457-2 to assess the potential water pollution from AMW. However, to facilitate preliminary hazard assessment of the potential leaching, especially for daily practice at sites with a large amount of recorded AMW, a comparative assessment of these widely used leaching tests can be helpful. The present research covers this knowledge gap by evaluating the geochemical leaching behavior of As, Ba, Cu, Pb, and Zn, by using these leaching tests in different types of AMW. The results suggest that these methods show slight differences in saturation indices, pH, specific conductance, redox potential, and released PTEs that can be mainly imputed to the contact time. Despite these differences, the findings suggest that the lixiviation patterns from the analyzed methods are comparable, and allow the same conclusions to be reached regarding the potential hazard of the AMW as a function of the solubility of the PTEs. [ABSTRACT FROM AUTHOR]

This study focused on acid neutralization reactions and the effects of water composition on the release and mobility of metals from mine tailings. The aims of this study were to: investigate leaching of metals from neutral mine tailings, determine the factors responsible for metal leaching, and investigate potential metal filtering by the soil. Tailings and soil samples were collected from an iron mine and analyzed. Equilibrium thermodynamic data and metal fractionation were then used to predict precipitation/dissolution of minerals and ion adsorption/desorption. Three column experiments were designed. The first column was filled with tailings, while the second column contained tailings above a layer of soil; both were leached with distilled water as rainfall. The third column was packed with soil and percolated with synthetic groundwater. The results indicated that iron (Fe) and zinc (Zn) mobility are mainly controlled by precipitation-dissolution mechanisms, while sorption onto oxides and carbonates limit the mobility of copper (Cu) and nickel (Ni). Cadmium (Cd) and manganese (Mn) mobility are affected by both mechanisms. Water discharging from column 3 (soil washed with groundwater) contained high concentrations of dissolved metals, indicating that water composition played an important role in metal mobility. Buffering minerals like carbonates and hornblende, chlorite, and albite decreased acid generation. [ABSTRACT FROM AUTHOR]

The effects of grain size distribution, initial flow rate, and initial pH were simulated using PHREEQC to determine how these factors affect the transport of Cd, Ni, and Mn from the tailings of the Zanjan zinc (Iran) leaching plant. Not surprisingly, lower pH, higher flows, and smaller effective particle size increased metal transport. The simulation results generally agreed well with results from a previously conducted column study. [ABSTRACT FROM AUTHOR]