Remediation of Mine Tailings, Ashes, Sediments, and Sludge

Recently, copper mine tailings have been treated by the EKR and electrodialytic remediation (EDR) methods in laboratory scale by different investigators (Kim and Kim, 2001 Hansen, Rojo, and Ottosen, 2005). 

Hansen et al (2007) found that recently produced tailings were much more difficult to remediate than tailings deposited more than 30 years ago. The important difference between the two tailing samples is the pH the fresh tailings are approximately neutral, while the old deposited tailings are acidic. This is due to the oxida- 

In the old tailings, copper was removed easily from the tailings due to the dissolution of the copper sulfides. This corresponds well with the findings from the sequential analysis of these tailings (Hansen, Yianatos, and Ottosen, 2005), where the mobility of copper in old tailings was found to be highest. 

Sediments and soils have many characteristics in common. However, commonly, sediments are fine grained, rich in organic matter, and more homogeneous than surface soils. Furthermore, sediments of saline waters are rich in salts (chloride), while freshwater sediments of eutrophic waters are rich in phosphate. 

Recently, the potential of using electrochemical methods for treatment of freshwater sediments was documented in an electrochemical cell, where the metals were transported from the acidified sediment in which carbon rod anodes were placed directly, and into the catholyte separated from the sediment by a cellulose filter (Matsumoto, Uemoto, and Saiki, 2007). Removal percentages of 18, 21, 53, 81,86, and 98 for Pb, Cu, Ni, Cr, and Zn, respectively, were obtained after 10 days of treatment at 2.9 mA/cml Another work proved that Cu can be removed (up to 85% after 14 days with 0.15mA/cm ) from artificially contaminated lake sediments, and that the use of nylon membranes and cation exchange membranes as barriers between sediment and cathode improves the treatment (Virkutyte and Sillanpaa, 2007). By means of the electrodialytic method also used for treatment of harbor sediments, it was shown that removal of Pb, Zn, Cu, Cr, and Ni could be obtained from industrially contaminated millpond sediment, with removals of approximately 95%, 85%, 75%, 65%, and 55%, respectively, after 14 days of treatment at 0.8mA/ cm (Jensen, Ottosen, and Villumsen, 2007). 

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