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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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Cyanide is a highly toxic and hazardous pollutant commonly found in the wastewater generated by mining, electroplating, and petrochemical industries. The current research aims to evaluate the efficiency of advanced oxidation techniques such as UV, O₃, and UV/O₃ combination, to eliminate cyanide from synthetic wastewater. All experiments were conducted in a semi-continuous reactor to investigate the impact of various operating conditions, such as initial cyanide concentration, reaction time, reaction kinetics, and pH. In this study, degradation tests were conducted on cyanide at four different concentrations (50, 100, 200, and 250 mg/L) and two pH levels (10 and 11). The reaction duration ranged from 0 to 90 minutes, with varying lengths. All experiments maintained constant operational parameters for the process, except for the variable being tested. The UV process alone is not very effective in removing cyanide from wastewater. This is because the low absorption coefficient of cyanide in the ultraviolet region limits the performance of UV in cyanide degradation. Additionally, cyanide is a relatively stable compound that requires a high amount of energy to break bonds and destroy them. Therefore, the use of the UV process alone is insufficient for the complete and safe destruction of cyanide from wastewater. It is necessary to combine it with other advanced oxidation processes to effectively remove cyanide from wastewater. According to the results, it was found that the effectiveness of removing cyanide through a single ozonation process was higher at pH 11 as compared to pH 10. The optimal conditions for achieving the highest level of cyanide removal, which is 68%, were found to be a single ozonation process with an initial concentration of 50 mg/L and a reaction time of 80 minutes. The higher efficiency of cyanide degradation at higher pH can be attributed to the greater production of hydroxyl radicals, resulting in an increase in the oxidizing power of the process. The efficiency of cyanide degradation in synthetic wastewater can be greatly improved by using the combined UV/O₃ process. In this method, the rate of cyanide degradation is higher when the pH value is lower. This is because the integrated UV/O₃ method is strongly dependent on the concentration of hydroxide ions and hydroxyl radicals, which are affected by the pH value. Therefore, the effect of pH value on the efficiency of cyanide degradation by the combined UV/O₃ method is significant. When UV and O₃ were combined, over 50% degradation occurred in 40 minutes due to increased degradation rate. The highest efficiency for cyanide degradation was achieved at pH 10 and an initial concentration of 50 mg/L using the combined UV/O₃ method. The reaction time was 50 minutes and the efficiency was 100%. First and second-order kinetic analyses were conducted for UV, ozone, and combined processes to study their effectiveness in cyanide degradation. The results showed that the combination of UV and ozone was the most effective method for total cyanide degradation from wastewater compared to the other processes studied. Therefore, UV/O₃ can be considered as the optimal analytical method for cyanide degradation from wastewater.