Abstract
Safe disposal of tailings as high-density thickened tailings or paste tailings can reduce the environmental risks of conventional tailings deposits, reduce water use, minimize tailings storage facility footprints, reduce the potential for acid mine drainage (AMD), and minimize risks of failure, among other advantages. In the dewatering process, the addition of flocculants is key to improving the sedimentation of the tailings and the formation of a compact paste. Despite the environmental and operational advantages of using paste tailings, it is not clear how the chemical nature of coagulants and flocculants could influence the discharge of toxic elements (salts and metals) from tailings after storage. In this study, we show the results of the real-time evaluation of the release of polluting runoffs from a paste tailings deposit. To do this, we analyzed paste tailing samples for AMD potential through static and kinetic tests and monitored the electrical conductivity and real-time pH, evaluating the correlation with the sulfate in the thickener and downstream from the tailings deposit. Tailing samples have low sulfur content (<2%) and low acid-generating potential. Moreover, there is no evidence of a significant positive correlation (Pearson’s coefficient r < 0.8) between the sulfate concentrations with the pH or EC. Thus, the chemical nature of the paste tailings prior to discharge has no direct impact on the release of sulfate-rich runoffs from the tailings after its storage. This indicates that the tailings paste at the evaluated site is chemically stable in the short term.
Highlights
Our results show that paste tailing samples are not potentially acid-producing, or the presence of neutralizing minerals is sufficient to limit the generation of acid runoffs released by the oxidation of minerals from the surface samples of tailing deposits
The results show that the pH values of the leachates remained in neutral-alkaline ranges during the operation (6.86–9.54 T4; 6.55–9.21 T6) while the electrical conductivity showed high values during the first cycles, reaching a maximum of 7042 mS/cm for T4 and 5485 mS/cm to later stabilize at values between 70 and 400 mS/cm for both cells and from the third cycle onwards
The potential of acid mine drainage (AMD) generation of paste tailings was evaluated by using Net Acid Generation (NAG), Acid Base Accounting (ABA), paste pH, and Kinetic tests
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In northern and central Chile, several mining operations are widely extended [1]. These activities generate large amounts of tailings that must be disposed of properly, in order to limit the effects on surrounding environments [1,2]. Mineral waste is typically deposited in waste repositories referred to as tailing storage or tailings dams. Tailings are characterized by low pH, high salinity, and varying amounts of metals and metalloids [3]
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