Enhancing interfacial regulation by S/O co-doping for oil–solid and oil–water separation at room temperature

The low recovery rate of petroleum and the inevitable formation of large quantities of oil–water emulsions limit the efficiency of petroleum production, transportation, and storage. To address these issues, four nonionic interfacial regulators (PA-1, PA-2, PAMA-1, and PAMA-2) were developed by incorporating oxygen atoms into a polyether substrate via esterification and polymerization reactions. Additionally, PAMA-1 and PAMA-2 were further modified with sulfonyl groups. Experimental results demonstrated that all regulators exhibited high-efficiency cleaning and demulsification performance at 25 °C. These regulators achieved 100 % oil removal from mineral and metal surfaces without causing damage. Furthermore, they could effectively break different kinds of water-in-oil (W/O) emulsions. It is also found that over 95.33 % dewatering rate could be achieved at 20 °C in 15 mins when PAMA-1 (600 mg/L) is added into asphaltene-stabilized emulsion and complete dehydration (100 %) within 40 mins. These interfacial regulators possess high interfacial activity and are rich in polar groups (–COOR, –OH, O = S = O, –C–O–C–). Mechanistic studies revealed that the heteroatomic groups introduced into the regulators serve as active sites for noncovalent interactions reconstruction, forming hydrogen bonds with natural interfacially active substances (e.g., asphaltenes) and water molecules. This promotes oil dispersion on solid surfaces and disrupts the oil–water interfacial film, improving cleaning and demulsification efficiency. Importantly, pre-treatment with these interfacial regulators effectively prevents emulsion formation. These regulators hold significant potential for applications in oil–water and oil–solid separation processes during petroleum exploitation.