Abstract
Background: Leachate contains toxic and non-biodegradable substances that are not easily treated by conventional treatment methods. This study investigated the effect of pH, current density, and reaction time parameters on the removal of cyanide (CN- ), nitrate (NO3- ), turbidity, and chemical oxygen demand (COD) from leachate by electrocoagulation process. Methods: This study was an experimental one with direct current using four parallel bipolar aluminum electrodes with 90% purity. The length, width, and thickness of the electrodes were 5 cm, 10 cm, and 2 mm, respectively. There were 6 holes with a diameter of 0.7 cm on each of the electrodes. The samples were prepared from the old leachate of solid waste landfill in Ghaemshahr, Iran. Results: In this study, at a current density of 33 mA/cm2 and a time of 60 minutes, the optimum removal efficiency of cyanide (100 %) was obtained at pH 5.5 and pH 10. Moreover, the maximum removal of nitrate (99.65 %) and turbidity (86.41 %) were at pH 5.5 and pH 8.3, respectively and the highest removal efficiency of COD (83.14 %) was obtained at pH 10. Conclusion: The results showed that the removal of cyanide, nitrate, turbidity, and COD increases with increasing current density and reaction time. Due to the proper removal of nitrate and cyanide from leachate by electrocoagulation, nitrate and cyanide amounts were less than the allowable contamination level. Based on the results, electrocoagulation is considered an efficient and effective method for removing nitrate and cyanide from old leachate of municipal solid wastes.
Highlights
Sanitary landfilling is the most common method of solid waste disposal due to its simplicity and low investment and operation costs [1]
The results showed that the removal of cyanide, nitrate, turbidity, and chemical oxygen demand (COD) increases with increasing current density and reaction time
This study aimed to evaluate the effectiveness of electrocoagulation process in removing cyanide, nitrate, turbidity, and COD from the old leachate produced from municipal solid waste to reduce the risks of these pollutants on human and environmental health
Summary
Sanitary landfilling is the most common method of solid waste disposal due to its simplicity and low investment and operation costs [1]. Sanitary landfilling is a complex and heterogeneous physical, chemical, and biological system in which waste materials are decomposed under the influence of compaction, humidity, temperature, and other environmental parameters [1,2]. In this biological decomposition system, a malodorous dark liquid with distinctive quantitative and qualitative properties is produced which is called leachate. This study investigated the effect of pH, current density, and reaction time parameters on the removal of cyanide (CN-), nitrate (NO3-), turbidity, and chemical oxygen demand (COD) from leachate by electrocoagulation process. Electrocoagulation is considered an efficient and effective method for removing nitrate and cyanide from old leachate of municipal solid wastes.
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