Testing pulsed electric fields in electroremediation of copper mine tailings

• Published in: Electrochimica acta Vol. 52; no. 10; pp. 3399 - 3405
• Main Authors: Hansen, Henrik K., Rojo, Adrian
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 25-02-2007; Elsevier
• Subjects: Aged tailings; Applied sciences; Copper removal; Cyclic process; Electrodialysis; Electrokinetics; Exact sciences and technology; Fresh tailings; Other industrial wastes. Sewage sludge; Pollution; Wastes; Cyclic process; Fresh tailings; Copper removal; Electrokinetics; Aged tailings; Electrodialysis; Pulsed current; Waste treatment; Transition metal; Electroremediation; Tailings; Operating conditions; Industrial waste; Copper; Electric field effect; Mining industry; Mining waste
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2006.07.064

Mining processes, prior to pyrometallurgical copper production, generate large amounts of solid waste, which are and have been deposited in mine tailings impoundments. This work is based on three electrodialytic (EDR) and four electrokinetic (EKR) remediation experiments on fresh and aged copper mine tailings using pulsed electric fields. The EDR results are compared to conventional remediation with direct current (dc) electric field. Applying pulsed electric fields in EDR, it was found that the remediation time decreased compared to dc EDR. In the anode side of the cell, 72
h of remediation at 20
V with a frequency ≥28
cycles/day at a fixed time ratio (
t
ON/
t
OFF) of 20, in terms of copper removal would correspond to around 270
h of dc remediation time. With both EDR and EKR of 120
h, at 14
cycles/day, the copper removal is practically uniform in the whole cell. Increasing the frequency to ≥28
cycles/day, the copper removal in the anode side is improved, and in the cathode side an accumulation is observed. With an EKR of 240
h, a larger copper accumulation in the cathode side was observed due to precipitation of copper hydroxide. In EDR with a pulsed electric field, the transport across the cation exchange membrane becomes the rate determining step. This can be seen from: (a) accumulation in the cathode side when increasing the frequency and (b) similar total copper removal for the three frequencies studied. In EKR, free alkali diffusion into the cell occurred. This generated copper precipitation in the cathode side, and the effect of the pulsed electric field on total copper removal was reduced.