Ultrasonic assisted surfactant/HPAM synergistic purification of highly emulsified oilfield produced water

Demulsification methods are extensively applied in oily wastewater treatment. However, traditional demulsifiers show limited efficacy on highly emulsified alkaline-surfactant-polymer (ASP) flooding-produced water, failing to meet reinjection standards. This study introduces an innovative treatment process combining ultrasonication, adsorption-demulsification, and induced flocculation to purify ASP flooding produced water efficiently. Short time ultrasound can quickly destroy the stability of droplets, promote the coalescence of oil-in-water droplets, and provide extremely favorable environmental conditions for demulsification process. Experiments demonstrate that Cetyltrimethylammonium bromide (CTAB) efficiently demulsifies by leveraging its interfacial charge adsorption with petroleum sulfonates. Furthermore, CTAB actively adsorbs partially hydrolyzed polyacrylamide (HPAM), inducing flocculation. Leveraging this advantage significantly enhances the efficiency of oil and turbidity removal in produced water. With a dosage of 360 mg·L −1 , CTAB achieves oil and turbidity removal efficiencies of 98.9 % and 98.7 %, respectively. Additionally, this study details the treatment process's mechanism from a microscopic view, highlighting the molecular similarity between CTAB and petroleum sulfonates as key to its efficient demulsification and flocculation. This research is relevant for understanding oil-water separation mechanisms and offers innovative approaches for enhancing treatment technologies for highly emulsified oily wastewater, mainly ASP flooding produced water.