The used motor oil recycling is a well-known alternative of world-wide power resources conservation, with a growing importance in the context of the limited resources of fossil fuels. At the same time, it represents a viable way of protecting the natural environment. The research investigates the effect of different alcohols used in acid treatment of used motor oil and the influence of the bleaching treatment on the properties of the regenerated oil. The used motor oils are contaminated by contaminants and impurities resulted from undesirable oxidation processes: sediment, water, metallic particles and degraded additives. The regeneration of used oil implies the removal of the contaminants. There are several recycling methods; the present research follows the basic steps: acid treatment to remove gums, greases etc., sedimentation/decantation, bleaching, neutralization, sedimentation/decantation and filtration. The used oil samples subjected to the experiment are drawn from the automotive service stations. Various acids (sulfuric acid, acetic acid, nitric acid, phosphoric acid, formic acid) are used in acid treatment. The bleaching is achieved by industrial bleaching earth (bentonite). Hydrated lime is employed in neutralization. For each different procedure of treatment, at the end of sedimentation/decantation and filtration, regenerated oil is obtained. The following determinations have been made for its properties: kinematic viscosity, flash point, specific gravity, TAN and color. The values of these characteristic parameters of the regenerated oil are presented compared to those of used and fresh oil. The results show variations of the measured properties which depend both on the type of acid used and the source of waste oil.
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