Comparision of Removal Efficiency of Cyanide by Chemical and Electrochemical Precipitation Process from Industrial Wastewater

Cyanide is a highly toxic compound which is found normally in the wastewater of numerous industries, such as Electroplating. The release of this compound into the environment has a lot of health hazards. The Purpose of this study was to compare the electrochemical oxidation efficiency with chemical precipitation method for cyanide removal from industrial wastewater. This study was conducted experimentally in a pilot system. In this study, the optimum conditions such as pH, Fe/CN- and reaction time were investigated in the Ferrous Sulfate precipitation method for cyanide removal from wastewater of electroplating industries by the use of jar test. It also investigated the effect of pH, voltage and operation time for total cyanide removal by electrochemical oxidation method by applying a stainless steel as an anode and copper as a cathode. And finally, the efficiency of two methods was compared. In the Ferrous Sulfate Precipitation method, the optimal conditions were obtained for the removal of cyanide at (pH 6/5, and 10:1 Molar Ratio and Operation Time 60 minutes). In these conditions, the removal efficiency was 93 percent. In the electrochemical method, the optimal conditions were obtained at the voltage of 9V and pH=13 and the operation time of 90 minutes in which the average percentage removal of cyanide was about 88 with SD=2.43. The results statistically confirmed the significant relationship between cyanide removal efficiency and optimal conditions in both methods (p< 0.05). But comparison of the two methods showed that the cyanide removal efficiency in the electrochemical method was as much as the chemical precipitation method. Due to the high cyanide removal efficiency and achieving the standards for effluent disposal to the environment, it seems that ferrous Sulfate precipitation method is more useful.