1- Master of mining engineering, Mining and Environment, Tarbiat Modares University
2- 2- Faculty of Engineering, Department of Mining and Environment, Tarbiat Modares University. ,ajamshidi@modares.ac.ir
3- Department of Mining and Environmental Engineering, Faculty of Engineering, Tarbiat Modares University
2- 2- Faculty of Engineering, Department of Mining and Environment, Tarbiat Modares University. ,
3- Department of Mining and Environmental Engineering, Faculty of Engineering, Tarbiat Modares University
Abstract: (292 Views)
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.
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