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The analysis of Cu distribution in pre-treated mine tailings after electrodialytic remediation was carried out by using two methods of sequential extraction. The initial content of copper in the tailings was 1109 mg Cu/kg of dry tailing, where close to 40% of the sample in weight corresponded to a soluble fraction. The tailing was treated with a leaching solution for 24 h. Three different solutions were tested: H 2 SO 4 + HNO 3 with pH = 1.9; H 2 SO 4 + HNO 3 with pH = 4.2; and NH 4 Cl 0.8 mol/L with pH = 5.5. After that, electrodialytic remediation experiments were carried out using an electric field of 2.7 V/cm for 15 days. The best performance for the complete cell was obtained with H 2 SO 4 + HNO 3 solutions, with a copper removal efficiency in the range of 62% to 67% and a current efficiency between 6% and 9%. The results of the remaining copper concentration between anode and cathode, from both procedures of sequential extraction, showed similar trends. The differences were mainly attributed to the use of different extractant solutions and extraction times. Soluble and exchangeable fractions were easily removed, with efficiencies higher than 80%. The lowest copper removal efficiency was obtained with NH 4 Cl 0.8 mol/L.

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.

In Chile, the budget for managing environmental liabilities such as abandoned tailings impoundments is limited. Using native and endemic plant species to remove heavy metals from tailings represents a low-cost alternative. Ex situ phytoremediation experiments were conducted over a period of seven months. The endemic species Lycium chilense and native species Haplopappus foliosus were used to remove copper and lead from mine tailings. The results indicate that both species can concentrate levels of Cu and Pb higher than the toxicity threshold in the roots and aerial parts, and present high removal efficiency for Cu higher than 50%. In both species, the concentrations of the target elements are higher in the roots than in the aerial parts. Haplopappus foliosus presents the best performance, accumulating higher concentrations of Cu and Pb than Lycium chilense, and presenting a bioconcentration of over one for Cu. [ABSTRACT FROM AUTHOR]

Heavy metal exposure from wastewater is an important environmental issue worldwide. In the search for more efficient treatment technologies, biosorption has been presented as an alternative for contaminant removal from wastewaters. The aim of this work is to determine the operation parameters of copper adsorption followed by biosorbent regeneration. The algae Durvillaea antarctica and Lessonia trabeculata were used as biosorbents in batch experiments. These biosorbents were exposed to different conditions, such as pH, copper concentration, exposure time, mass-to-volume ratios and regeneration reagents. Batch sorption tests revealed an adequate pH of 4.5–5.0. The selected biosorbent was D. antarctica due to a considerably higher copper retention capacity. As a regenerating reagent, sulfuric acid was more efficient. For diluted copper solutions (10 to 100 mg L−1), a biosorbent particle size of between 1.70 and 3.36 mm showed better retention capacity than larger particles and a biosorbent mass-to-volume ratio of 10 g L−1 was desirable for these metal concentrations. [ABSTRACT FROM AUTHOR]

In the present study, the assessment of heavy metal contaminant migration from fresh mine tailings was conducted using the electrokinetic remediation technique (EKR). In this sense, a pilot EKR cell was designed to evaluate the recovery potential of copper, nickel, and cobalt species. In particular, the focus was on the impacts of electric field intensity and pH in initial mixture and testing their interaction in copper, nickel, and cobalt migration. Experiments were made using a 22 factorial experimental design with a central point, using DC electric fields from 1.0 to 2.0 V cm−1 and H2SO4 pretreatment solutions from 1.0 to 2.0 mol L−1, along with an ANOVA test with error reduction. The metal removal rates were approximately 7% for cobalt, neglectable for copper, and 6% for nickel. In the best cases, the highest concentrations by migration at the cathodic zone were 11%, 31%, and 30%, respectively. According to ANOVA tests, factor interaction was proven for each metal in the half cell near the cathode and the closest zone from the cathode specifically. Both factors affected metal concentrations, which indicates that when the goal aims for species accumulation in a narrower section, each factor has a significant effect, and their interaction makes a proven enhancement. Thus, using 2.0 V cm−1 and 2.0 mol L−1 showed a high improvement in metal concentration in the cathodic zone. [ABSTRACT FROM AUTHOR]

In this work, a continuous multistage electrodialytic technique is evaluated as a possible treatment of copper smelter wastewater. Six experiments with different values of feed flow rate, current density and treatment time were carried out. It was possible to concentrate copper during experiments and a maximum recovery of 10% was achieved. The experiment with a feed flow rate of 30 mL min −1 , current density of 300 A m −2 and a treatment time of 2 h was the most efficient, with a copper recovery of 5.1%. In sections where copper was concentrated, a solution with mCu/mAs ratio around 2 was obtained, this value is substantially higher than 0.1, which is the value for a mining wastewater. [ABSTRACT FROM AUTHOR]