Research on the treatment of Active Black KN- B wastewater by electro-coagulation method using iron and aluminum electrode with alternate pulse

In order to avoid the disadvantages of unilateral current such as anode wastage and high cost in the application of electro-coagulation method for dye wastewater treatment,alternate pulse electro -coagulation was used instead to treat the simulated Active Black KN-B dye wastewater.Decoloration capability and the removal of chemical oxygen demand(COD)of the simulated dye wastewater were evaluated for the utilization of iron and aluminum as opposite electrodes in electro-coagulation system.In this method either anode or cathode will dissolve when the alternate pulse from the electrical source was applied.The ions which possess the ability of flocculation will be produced at the same time.Hence,the anode will be protected and the consumption of electrode will be slowed down.The effect of different operational parameters such as the electrolysis time,applied voltage,alternate cycle,stirring speed,initial pH and dye concentration, electrode gap as well as the concentration of electrolyte were studied in order to achieve higher dye removal efficiency.The experiment results showed that the optimum operating conditions were as follows:electrolysis time=30 min,voltage=10 V,alternate cycle =10s,stirring speed=1000 r/min,dye concentration=100- 300 mg/L,concentration of electrolyte(Na_2SO_4)=0.01 mol/L, electrode gap=1.0 cm and initial pH=5-9.Decoloration rate can go up to 99% and the removal rate of COD_(Cr)was 50% and above. All of the parameters can affect the decoloration and the removal of chemical oxygen demand(COD)with different extent.Decoloration is mainly due to the chemic reaction of the Active Black KN-B dye, where the configuration of-N=N-was altered and phenyl ramification was formed.The removal of COD_(Cr)was resulted from the flocculation and floatation.The SEM characterization showed that the consumption of electrode can be effectively slowed down by this method.