Abstract
Mine tailings have been analyzed by a sequential extraction procedure after their pre-treatment with a leaching solution for 24 h and electrodialytic remediation during 15 days with a constant electric field of 2.7 V cm−1. Four leaching solutions were tested: H2SO4 + HNO3 (2:1 vol.) pH = 1.9; H2SO4 + HNO3 (2:1 vol) pH = 4.2; NH4Cl 0.8M, pH = 5.5 and 30% H2O2 adjusted to pH 2 with HNO3 1M + HCl 1M. After the treatment, the tailings were divided in six slices from anode to cathode. The highest removal efficiency of copper was obtained with H2SO4 + HNO3 pH = 1.9, which allows one to remove 67% of the copper in the total cell and 85% of the copper in the slice closest to anode. The same solution with pH = 4.2 allows one to remove 62% of the total copper. The analysis realized by the sequential extraction method indicates the easy removal of water-soluble and exchangeable fractions in all experiments, moreover, residual and sulfide are the less mobile fractions. The general trend was the movement of copper associated to different fractions from anode to cathode and its accumulation closest to the cathode in the case of exchangeable, Fe-Mn oxides and acid soluble fractions, possibly due to some precipitation of copper compounds associated with less acidic conditions.
Highlights
Mine tailings have become a focus of attention due to their environmental impacts
Taking into account the complete cell, the highest removal efficiency was obtained with the pre-treatment solution of H2 SO4 + HNO3 with pH = 1.9; this solution makes it possible to remove 85%
A little lower copper removal efficiencies were obtained with the same solution with a pH = 4.2, in this case, 78% of the total copper was removed in the slice closest to the anode and 62% in the complete cell
Summary
In Chile, tailings are mainly associated to the copper sulfide concentration process and to a lesser extent to the concentration of gold minerals They are a mixture of fine-grained ground-up rock and process water with dissolved metals and reagents that remain after the minerals of economic importance have been extracted [1]. Some advantages of electrokinetic remediation include the possibility of using this technique in soils with low permeability, in situ remediation and low cost compared to other traditional remediation technologies, its practical application has limitaions, such as lower removal efficiencies and longer treatment times [2]. Several chemical reactions are induced by the application of electric fields, where the descomposition of water at the electrodes is the
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