Efficient Reclamation of Base Oils from Spent Lubricants Using Novel Ternary Solvent Combinations

To address the environmental hazards of improper disposal of used engine oils and reduce reliance on fossil resources, this study investigates a novel approach for recovering base oils from spent lubricants using two innovative ternary solvent systems. System (a) comprised acetonitrile (35 vol.%), xylene (40 vol.%), and n-heptane (25 vol.%), while system (b) included dimethyl sulfoxide (35 vol.%), toluene (40 vol.%), and n-hexane (25 vol.%). A series of laboratory-scale extractions was performed under varying solvent-to-oil ratios (1:1 to 6:1 wt./wt.), temperatures (60–90°C), and mixing durations (15–60 min), with constant stirring at 500 rpm. The extracted oils were bleached using hydrogen peroxide (5–15% v/v) and activated bentonite (1–5 g.100 mL-1). System (a) exhibited superior performance, achieving a maximum base oil recovery of 86.6% at 70°C, 6:1 ratio, and 60 minutes, compared to 74.4% for system (b) at 80°C under the same conditions. The use of tailored ternary solvent systems combining polar and non-polar components highlights a novel and efficient approach to oil regeneration. Beyond high recovery yields, this method offers clear environmental advantages and industrial scalability, supporting sustainable waste oil management.