Novel polyether-polyquaternium copolymer as an effective reverse demulsifier for O/W emulsions: Demulsification performance and mechanism

This study reports a novel polyether-polyquaternium (PPA) demulsifier for demulsifying the O/W emulsion that originating from alkaline-surfactant-polymer (ASP) flooding produced wastewater. When processing an O/W emulsion that contained 500 mg/L oil, this PPA demulsifier exhibited a demulsification efficiency of 80.6% at 110 mg/L dosage, which is higher than that of a commercial polyamine demulsifier (65.9%) (designated S-01). This remarkable demulsification efficiency was ascribed to its abilities to reduce interfacial tension, thin interfacial films, reduce the elastic modulus and neutralize negative charges of the interfacial film. Oil droplets size distributions test results indicated that PPA could better aggregate the small oil droplets, which significantly favors the oil-water separation efficiency. By combining high-speed microphotography with the single-droplet method, the rupture kinetics data of the interfacial film were measured, which agreed with the demulsification principle of these two demulsifiers at various dosages. The microtopography difference of the original and demulsified interfacial film was also monitored using an atomic force microscope. Furthermore, the demulsification mechanism has been explored and confirmed according to all the characterization results. This novel integrated PPA reverse demulsifier with its high demulsification efficiency offers technical promise for oil removal from the ASP flooding produced wastewater.