College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao, 266580, China; Shandong Provincial Key Laboratory of Oil & Gas Storage and Transportation Safety, Qingdao Key Laboratory of Circle Sea Oil & Gas Storage and Transportation Technology, Qingdao, 266580, China. Electronic address: [Email]
This work aimed to quantify the contribution of electrocoagulation(EC) mechanisms on emulsified oil removal from polymer-flooding sewage (PFS), and also to quantitatively compare the performance of EC, anode-electrocoagulation(AEC) and chemical coagulation(CC) on PFS treatment. An apparatus which introduced the salt bridge was proposed to help separate the anode and cathode. To quantify the contribution of coagulation and oxidation individually, the EDTA, a chemical addictive which can inhibit the ability of Al3+ was added to shield the effect of coagulation. The experimental results show that in the PFS treatment by EC method, about 80% of emulsified oil in anode zone was removed by coagulation while only 11%-13% was oxidized; In cathode zone, about 13%-14% of the oil was removed by flotation. Besides, the results suggest that the separation of anode and cathode not only result in the low demulsification efficiency but also generated the fragile flocs. During the comparison and contrast of purification performance of EC, AEC and CC, the effects of treatment time and current densities(aluminum doses) on oil removal was investigated, the pH and absorption spectra evolution over time were also analyzed. The results showed that under all conditions studied, the EC performance outperforms AEC and far beyond CC.