The Effect and Mechanism of Electrocoagulation and Ozonation Processes on Demulsification of Simulated Polymer-Flooding Produced Water

Produced water derived from polymer flooding systems contains surface-active substances and polymers, posing significant challenges to oil–water separation. In this study, the single and coupling processes of electrocoagulation (EC) and ozonation (O3) were used to treat simulated polymer-flooding produced water. And the coupling process demonstrates a notable improvement in treatability. Through systematic characterization including zeta potential, static separation behavior, and floc morphology, the demulsification mechanism was elucidated. In the coupling process, ozone breaks down the hydrolyzed polyacrylamide (HPAM) molecule, and the viscosity of the solution decreases. The polarity of the HPAM chain is also changed, causing it to desorb from the oil–water interface, weakening the interface hydration membrane. So, the zeta potential reduced to −41.4 mV after 3 min of treatment. The Al3+ released by EC compresses the electric double layer and accelerates the merging of oil droplets. With optimized conditions (ozone dosage of 30 mg/L and current density of 9 mA/cm2), the system achieved a viscosity reduction to 1 mPa·s, accompanied by an increase in the mean oil droplet size to 30 μm. Following 30 min of static separation, the maximum oil removal efficiency reached 94%. Such a process could shorten the retention time of the traditional process by over 80%.