biostudies-literatureUnknown10(45)Li XThe reduction and harmless treatment of oily sludge are challenging tasks. As green solvents, ionic liquids (ILs) have been used to treat oily sludge effectively; however, their high price limits the applications. In this paper, an imidazolium-based IL 1-hexadecyl-3-methylimidazole chloride salt ([C₁₆mim]-Cl) was synthesized and compounded with Tween20 to obtain a composite surfactant that could be used as an emulsifier to prepare a microemulsion for the treatment of oily sludge. The composite surfactant exhibited the greatest synergistic effect at a mass ratio of 4:6. Under optimal conditions, the oil removal rate reached 94.90%, and the residual oil rate was reduced to 1.67%. Moreover, the microemulsion exhibited a high removal rate for asphaltenes (81.01%). The treatment mechACS omega54809-54817https://www.ebi.ac.uk/biostudies/studies/S-EPMC12631387biostudies-literatureSynergistic Mechanism of an Ionic Liquid-Based Composite Surfactant-Stabilized Microemulsion for Effective Separation of Oily Sludge.PMC12631387Li WLi XWang RWang SJiang HLv CLi QOuyang ZOu SZhang BfalseSynergistic Mechanism of an Ionic Liquid-Based Composite Surfactant-Stabilized Microemulsion for Effective Separation of Oily Sludge.The reduction and harmless treatment of oily sludge are challenging tasks. As green solvents, ionic liquids (ILs) have been used to treat oily sludge effectively; however, their high price limits the applications. In this paper, an imidazolium-based IL 1-hexadecyl-3-methylimidazole chloride salt ([C₁₆mim]-Cl) was synthesized and compounded with Tween20 to obtain a composite surfactant that could be used as an emulsifier to prepare a microemulsion for the treatment of oily sludge. The composite surfactant exhibited the greatest synergistic effect at a mass ratio of 4:6. Under optimal conditions, the oil removal rate reached 94.90%, and the residual oil rate was reduced to 1.67%. Moreover, the microemulsion exhibited a high removal rate for asphaltenes (81.01%). The treatment mech2025-01-01T00:00:00Z2025 Nov2026-06-05T17:05:37.544Z2026-05-19T03:11:54.952ZS-EPMC126313874128085410.1021/acsomega.5c08441