Electrokinetic remediation of mine tailings by applying a pulsed variable electric field

Abstract

Following the flotation step of copper sulphide mineral processing, a considerable amount of ground ore in the form of a pulp containing heavy metals and other polluting compounds is discarded as waste, known as “mine tailings”. This waste is deposited behind dams, and unless it is treated, it represents a danger to the environment because the natural oxidation of heavy metals makes the waste chemically unstable.Electrokinetic remediation (EKR) is a technology used to remove contaminants from soils. In recent years, the technology has been of research interest for stabilising mine tailings from the copper industry.Nine EKR experiments with pulses of sinusoidal electric fields (by applying simultaneously DC and AC voltages) and an AC voltage frequency of the order of kHz were performed to improve conventional EKR and stabilise synthetic tailings samples. The synthetic tailings were prepared based on representative data for tailings from a combined Cu–Mo concentrator plant.It was found that, in general, the use of a pulsed sinusoidal electric field favoured overall copper removal in the EKR cell, and particularly good results were observed when this type of electric field produced periodical polarity reversal in the electrodes.The best results in terms of overall cell removal and specific energy consumption were obtained under the following conditions: (i) effective voltage of 14.6V (VDC=10V and VAC=15V), (ii) AC voltage frequency 1000Hz, (iii) electrical field applied in pulses with a time ratio of 25.