ABSTRACT The present investigation proposes a comparative analysis for refining waste lubricating oil through extractive flocculation technique using composite solvent to maximize the yield. Experimental study reveals that with process constraints such as (i) reaction time of 80 min; (ii) reaction temperature of 80°C, (solvent to waste oil proportion of 80:20); (iii) coagulant dosage of 1 g/kg of solvent, maximum % yield of 94.45% was attained. Further, experimental results also portray maximum % sludge removal of 15.63% for the case of refined oil treated with composite solvent and bio‐based flocculant. Physicochemical properties of refined oil with composite solvent shows excellent characteristics that are close to virgin lubricant. The optimum recovery of high‐quality base stock with adaptation sustainable green principles can effectively mitigate the detrimental consequences of spent lubricant into the ecology and create energy efficient process for regeneration of base oil.
Sarkar et al. (2026) studied this question.