Electrochemical Oxidation Pretreatment Of Sorbic Acid Wastewater And Its Mechanism

In recent years, the electrochemical oxidation technology has been paid more and more attention because of its environmental friendly characteristics in pollutant control. Electrochemical oxidation technology has many advantages than other traditional methods, such as mild reaction conditions, simple operation, easy automation control, no secondary pollution, simple subsequent processing and combining with other processes, which shows a great advantage in refractory wastewater treatment. It has already become a hotspot in water pollution control field. At present, the electrochemical oxidation technology has been applied for treating leachate, leather, printing and dyeing, paper making, petrochemical and many other industrial wastewaters.Sorbic acid wastewater is a typically high salinity, refractory wastewater, which contains6～8%hydrogen chloride and60000-80000mg/L COD. First, an electrolytic cell deigned and constructed by ourself was applied for treat the sorbic acid wastewater. The anode and cathode of the electrolytic were made of the Ti/Ru, Ir, Ta plate and graphite plate, respectively. The distance between the two electrodes was2cm. The sorbic acid wastewatdr with initial pH10.0was electrolyzed for60min (the current intensity was5A) in the electrolytic cell, the ratio of BOD5to COD of the sorbic acid wastewater was increased from0.21to0.45. This indicated that the biodegradability of the sorbic acid wastewater has been significantly improved after electrolytic oxidation pretreatment. Then, the sorbic acid wastewater pretreated by electrolytic oxidation was aeration in the sequencing batch reactior (SBR) for12h, its COD removal efficience was over80%. Final, the effleuent of SBR was post-treated by coagulation and sedimentation, the supematant COD lvele would be less than the local discharge limit.In addition, the anodic oxygen evolution potential and chlorine evolution potential were determined and the mechanism of pollutant oxidation was also investigated by using cyclic voltammetry in this research. The results shown:the pollutants in sorbic acid wastewater is mainly oxidized indirectly during the electrolytic process because the chloride ion transfered into Cl2, HClO and ClO-, with strong oxidation potential.