Study On Treatment Of Electroplarting Wasterwater By Pulse Electrocoagulation

Electroplating wastewater is a typical heavy metals wastewater.Electrocoagulation is widely concerned due to the effective treatment technology for heavy metal wastewater.In this paper,the effect of pulse electrocoagulation on the treatment of electroplating wastewater was studied.According to the single factor test,the response surface method is used to optimize the process parameters,and finally the actual project construction and operation.By studying the removal rates of total chromium,hexavalent chromium and nickel in heavy metal wastewater with pH,current density,pulse frequency,duty cycle and aeration,the results show that the synergistic treatment of chromium and nickel by the electroflocculation technology with iron as the electrode plate can achieve better results.When the current density is 30 A/m~2,the pH is 7,the duty cycle is 45%,the frequency is 2000 Hz,and the aeration is 160 mL/min,the removal rates of hexavalent chromium,total chromium and nickel are 100%,99.7%and 99%respectively after 30 minutes of electrolysis.According to the single factor experiments,the current densities,pH values and duty cycles which have great influence on the removal rate and energy consumption are selected to optimize response surface to determine the optimum process conditions to ensure that nickel,hexavalent chromium and total chromium can meet the discharge standards.When the removal rate of nickel is the response value,the optimized process current density is 27.14 A/m~2,pH value is 7.1,duty cycle is 47.45%.After 30 minutes of electrolysis,hexavalent chromium and total chromium cannot be detected,and the concentration of nickel ion is 0.085 mg/L.When the removal rate of total chromium is the response value,the optimized process current density is 27.36A/m~2,pH value is 8.5 and duty cycle is 45%.After 30 minutes of electrolysis,hexavalent chromium and total chromium could not be detected,and nickel ion concentration was 0.14 mg/L.Based on the above studying,a pulse electrocoagulation device with a processing scale of 30 m~3/h was established.Considering the dynamic change of wastewater quantity and water quality,when the current density is 25?30 A/m~2,the duty cycle is 48%,the frequency is 2000 Hz,the influent pH value is 7,and the residence time is 20?30 min,the designed electrocoagulation device has been stable operation,the concentration of heavy metal ions in the effluent meets the discharge standard of Table 3 of the Electroplating Pollutant Emission Standard(GB21900-2008).The effluent nickel ion concentration is less than 0.1 mg/L,the total chromium effluent concentration is as low as 0.1 mg/L,hexavalent chromium is basically not detected.The comprehensive operating cost of the device is 2.16 yuan/m~3.