A low-temperature ionic liquid demulsifier derived from recycled PET waste plastics

The petroleum industry produces a large volume of water-in-oil (W/O) emulsion annually, which has detrimental consequences for both the industry and the environment. Therefore, effective demulsification of these emulsions is crucial. In current work, a low-temperature demulsifier (EBTA) for W/O emulsions was synthesized using PET waste plastic as starting materials through a simple method. Chemical structure of EBTA was characterized by FT-IR and 1H NMR. The demulsification performance was assessed using bottle-test method, and a comprehensive examination was conducted on the influence of EBTA concentration, settling time, temperature, pH value, and salinity on the demulsifying efficiency (DE). At a low temperature of 40 ℃ and a concentration of 250 mg/L, EBTA achieved a DE of 95.36% in an Emul30 emulsion, while a DE of 100% could be obtained in an Emul70 emulsion. Furthermore, EBTA demonstrated excellent tolerance for salts, acids and alkalis. In addition, the demulsification mechanism of EBTA was investigated using various techniques, such as interfacial tension (IFT), zeta potential, three-phase contact angle and coalescence time of droplets. The results revealed that EBTA had a lower IFT and was easily adsorbed on the oil–water interface. This led to the damage of the interface film and facilitated the oil–water separation. Due to the simple and safe synthesis process and remarkable demulsification performance, EBTA is a promising demulsifier for separating W/O emulsions.