Refining of used engine oil by solvent extraction and adsorption processes: A circular economy strategy

Abstract

To address the issues related to lubricating oil used in vehicles, present study is aimed to investigate the characterization of waste engine oil and its treatment using solvent extraction and adsorption methods. The motor oil sample used has been treated with different solvents and solvent ratios to analyze the effect of solvent type and oil-solvent ratio on sludge removal, density, and ash content. The results showed that methanol-based treatment at a 1:3 oil-solvent ratio gave the best-refined oil, with a maximum sludge removal of 54% and a significantly lower density (0.874 g/ml) and ash content (0.54%). Additionally, the study employed adsorption as a further purification method, and the results indicated that an adsorbent dosage of 2.5 g per 50 ml of solvent-extracted oil at a temperature of 60°C gave the best-refined oil, with a 99% removal of metals as contaminants. The waste and treated engine oil have been characterized using various parameters, including density, viscosity, flash point, ash content, water content, and metal contents. The results indicated that the treated oil had comparable quality to the virgin oil, with a density of 0.871 g/mL, flash point of 210 °C, and ash content of <0.1%. The study's findings suggest that the solvent extraction and adsorption methods can be effective in removing contaminants from used engine oil, producing a refined oil of comparable quality to virgin oil. This study significantly impacts Ethiopia's environmental pollution reduction and energy conservation.