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There are known techniques for cyanide remediation from contaminated soil such as soil washing, soil oxidation and biological degradation. However, there is very little research for electrokinetic remediation of cyanide from soil. This study investigates the application of electrokinetic remediation to contaminated soil with high clay content and low coefficient of permeability. The experiments were conducted with two electrodes as cathode and anode poles, which were placed inside the soil using the direct electrical current. Thus cyanide ions were transported to the anode pole and caused the remediation of the soil. The contaminated soil from tailing dam of Takab gold processing plant was used. Contaminated soil with the concentration of 420 mg/kg, distilled water and NaOH were employed in the electrokinetic cell. The experiments were conducted on the optimum moisture content of clayed soil at two voltage gradients (1.0 and 1.5 VDC/cm for the duration of 7 and 14 days) in order to assess the effect of voltage gradient when employing 1M NaOH solutions and distilled water at the anode pole. For each test, cyanide removal efficiency, the pH of the soil, moisture content, electrical conductivity and the electrical current and flow were determined. The measurements were conducted for the entire duration of electrokinetic experiments and at the end of the test. The results indicated that the cyanide removal obtained in 7 and 14 days was approximately 65% and 80%, respectively. The results also showed the pH of the soil was changed from 8.83 to 1-2 for the anode and to 12-13 for the cathode pole. The cyanide transported to the cathode and the pH were the most important dominant factors for cyanide remediation.

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Microorganisms play an important role in formation of mines. In this research, the bacteria inhabiting in Aq-Darreh Takab gold mine were isolated and compared with agricultural soils. The isolates were characterized using 16S rDNA sequencing and the homology searches were performed using BlastN, EzTaxon, and RDP Classifier web tools. Resistance of the isolates was also investigated against arsenic and silver in the presence and absence of 3.5 ppm gold. Although the control soil showed a wide variety of bacterial diversity (43 isolates belonging to 13 genera), only 17 isolates belonging to 11 genera were isolated from mine soils including Acinetobacter, Agrobacterium, Comamonas, Deinococcus, Listeria, Microbacterium, Micrococcus, Pseudomonas, Rhizobium, Roseomonas and Staphylococcus. Among the isolates, A. radiobacter, D. ficus, M. antarcticus, M. luteus, R. radiobacter and R. selenitidurans were able to tolerate different amounts of arsenic and silver in the presence of gold, among which A. radiobacter and D. ficus showed the highest resistance in such a way that they grew in the presence of 50 ppm arsenic, 50 ppm silver, and 3.5 ppm gold. Our results showed that bacterial diversity in soils containing gold, silver and arsenic metals is less than agricultural soils. It was also found that the bacterial diversity in gold mines depends on the amount of gold and the amount and type of associated elements. Due to high resistance of two endogenous bacterial species to arsenic and silver, A. radiobacter and D. ficus, have also the potential for industrial purposes in environments contaminated with these metals.