Enhanced oil recovery from waste oily sludge using low-ratio solvent–surfactant systems based on toluene or chloroform with Triton X-100 and Triton X-114

Oily sludge (OS) is a hazardous waste containing a complex mixture of hydrocarbons, water, and solids, yet it retains a significant oil fraction that can be recovered through extraction processes. This study evaluates oil recovery from OS using solvent–surfactant extraction systems based on toluene and chloroform, combined with the nonionic surfactants Triton X-100 and Triton X-114, selected based on their favorable solubility parameters and low critical micelle concentrations. The effects of solvent-surfactant type, concentration, extraction temperature, and contact time were systematically investigated to analyze mass-transfer behavior, determine optimal, and energy-efficient operating conditions. The highest oil recovery (97.97%) was achieved using chloroform–Triton X-100 at a 1:60 ratio, and 100°C. However, comparable recovery was also obtained at moderate temperatures (60°C) by extending the extraction time (60 min), indicating that efficient extraction can be maintained while potentially reducing energy demand and safety concerns associated with high-temperature operation. FTIR, XRD, and SEM–EDX analyses confirmed effective oil removal and exposure of mineral phases after extraction. GC–MS results showed that the recovered oil was dominated by diesel-range hydrocarbons (C 10 –C 28 ) with minor amounts of heavier lube-oil fractions, suggesting potential suitability as a fuel-range feedstock, although additional upgrading may be required to remove heavy or heteroatom compounds. Overall, the proposed solvent–surfactant systems enhance oil separation and provides an efficient and operationally feasible recovery approach.