COSMO-RS Guided Sustainable Separation of Squalene from Soybean Oil Deodorizer Distillate Waste Using Biocompatible Ionic Liquids

Efficient recovery of value-added compounds from biomass waste represents a sustainable approach to chemical engineering. This study presents an innovative and environmentally benign approach for squalene purification from unsaponifiable soybean oil deodorizer distillate (SODD) waste using biocompatible ionic liquids (ILs) in a liquid–liquid extraction process. Employing a conductor-like screening model for real solvents (COSMO-RS)-guided methodology coupled with a push-and-pull strategy, we systematically screened and identified the optimal biphasic extraction systems. The optimized system utilizing 1 mol % [Ch][CnH2n+1COO] in N-methyl-2-pyrrolidinone achieved exceptional impurity-to-squalene selectivity over 15 while maintaining suitable distribution coefficients. Comprehensive mechanistic investigations through quantum-chemical calculations and nuclear magnetic resonance spectroscopy revealed a hydrogen-bond-dominated separation mechanism. Multistage extraction optimization demonstrated the capability to simultaneously achieve high purity and superior recovery rates of squalene. This research establishes a sustainable, high-performance pathway for valorizing refinery waste streams, offering significant implications for green chemistry and circular economy principles in the biorefinery industry.