Electrical Behavior of Copper Mine Tailings During EKR with Modified Electric Fields Adrian Rojo 1 • Henrik K. Hansen 1 • Omara Mona ´rdez 1 • Carlos Jorquera 1 • Paulina Santis 1 • Paula Inostroza 1 Received: 17 December 2015 / Accepted: 16 June 2016 Ó Springer Science+Business Media New York 2016 Abstract Electro-kinetic remediation (EKR) with sinu- soidal electric field obtained simultaneously with DC/AC voltage reduce the polarization of the EKR with DC volt- age. The DC voltage value defines the presence of a peri- odic polarity reversal of the cell and the electrical charge for electro-kinetic transport. In this case, the AC frequency favors the breaking of polarization conditions resulting from the EKR with DC voltage. However, with high fre- quencies a negative effect occurs where the tailings behave as a filter circuit, discriminating frequencies of an electric signal. The goal of this work is to analyse the electrical behaviour of tailings in EKR experiments. The conditions selected were: DC/AC voltages: 10/15 and 20/25 V (peak values), and AC voltage frequencies 50–2000 Hz. When the AC frequency reaches 2000 Hz, the copper removal tends to zero, indicating that the tailing behaves as a high- pass filter in which the DC voltage was filtered out. Keywords Electro-remediation Á Sinusoidal electric field Á Filter circuit Á Mine tailings EKR is an in situ treatment technology for restoring con- taminated hazardous waste sites (Acar and Alshawabkeh 1993). The conventional practice of this alternative treat- ment uses a DC electric field that generates a current through electrodes placed in a humid solid waste, thereby causing the mobilization and removal of contaminants (Probstein and Hicks 1993). Using this method, the applied electric field promotes transport of pollutants mainly by electro-migration and electro-osmosis in the solution con- tained in the pores of the contaminated waste. In the case of treating mine tailings, previous work (Rojo et al. 2006) has shown that the conventional DC system was limited with regard to metal removal efficiency and high electrical energy consumption. In this context, the chemical nature of the tailings is the main difficulty, because they are partially oxidized sulphides as a conse- quence of physical–chemical changes due to weathering and bacterial action during disposal. The dissolution and the subsequent transport of contaminants are therefore restricted to the oxidized species of the tailings. With a limited amount of the species available for the electro- kinetic transport, low removals and high energy con- sumption resulting from significant increases in polariza- tion over time can be expected. However, despite the limitations of the process for treating tailings from copper mining, due to the large amounts of the material accumu- lated in mining operations, EKR is a valuable tool for stabilizing this residue, removing pollutants from the oxi- dized species to mitigate the risks of contamination by leaching into nearby water aquifers. The use of this remediation technology will apparently imply the periodic application of an electric field to remove the soluble copper that will previously have been generated over time. The remediation action for this heterogeneous solid waste is to remove the oxidized copper in the tailings and in this way to make the final residue more stable. Under this scenario, sinusoidal EKR applying an electric field with the simultaneous application of DC ? AC volt- ages (Rojo et al. 2010, 2011, 2012, 2014) was investigated. In this case, the resulting electric field is a sinusoid with an offset corresponding to the DC voltage value (see Fig. 1), and the electro-kinetic transport is the result of the positive electrical charge obtained when DC ? AC voltages are & Adrian Rojo adrian.rojo@usm.cl 1 Universidad Te ´cnica Federico Santa Marı ´a, Casilla 110-V, Valparaiso, Chile 123 Bull Environ Contam Toxicol DOI 10.1007/s00128-016-1858-8