Treatment and Recycling of Used Lubricating Oil in Nigeria: Solvent Extraction Approach

Abstract

This study investigates the treatment of used lubricating oils sourced from an automobile mechanic's shop. Used lubricating oil, a by-product of machinery lubrication, poses environmental threats when improperly disposed of. Dumping such oil in landfills contributes to land and air pollution and can co taminate groundwater through percolation. Re-refining the used oil is proposed as a solution to mitigate these environmental concerns and offers economic advantages over producing lubricating oil from crude oil refining. The study focuses on re-refining using the solvent extraction method. This research employed two solvent mixtures: the first composed of Toluene, 1- butanol, and Methanol (TBM), and the second comprised Toluene, 1-butanol, and Ethanol (TBE). The initial treatment involved pretreating the used oil using a vacuum filter to eliminate solid impurities such as dust, soot, and metal fragments that may have contaminated the lubricating oil during use. The solvent extraction process commenced by introducing the TBM solvent mixture into the used engine oil at a 3:1 ratio, followed by stirring for 1 hour using a magnetic stirrer. The mixture was allowed to stand for 24 hours. The same procedure was repeated with a different sample using the TBE solvent mixture. The surface mixture containing the solvent and oil was decanted and transferred to a rotary evaporator to separate the oil from the solvent. The efficacy of both treatment methods was experimentally examined, considering various operating parameters such as different adsorbents, acids, and solvents used for treating the used oil. These parameters underwent thorough study and analysis. Quality assessment involved measuring and eval ating key characteristics, including viscosity, specific gravity, pour point, cloud point, metal content, and sulfur content. Upon comparing the results with the standards of fresh lubricating oil, both treatment methods demonstrated significant proficiency. The characteristics of the re-refined engine oil closely resembled those of fresh engine oil, in contrast to the untreated engine oil.