Recycling and characterisation of spent lubricating oil

Abstract

Ten samples of spent lubricating oil (SLO) were obtained from different road side mechanics in Minna, Niger State, Nigeria; five samples were collected from both premium motor spirit (PMS) and automotive gas oil (AGO) engines respectively. Samples were digested to reduce organic, hydrocarbon and organo-metallic compounds. Samples were analysed using atomic absorption spectrophotometer (AAS). Metals average concentration (ppm) in PMS and AGO samples were as follows: 1.1, 1.43; Iron 4.78, 10.10; copper 0.39, 0.19; zinc 10.5, 17.43; chromium 2.4, 3.83; magnesium 0.633, 0.60 and calcium 135.39, 128.06. Results showed that copper and magnesium were the least concentrated while calcium has the highest concentration. SLO was recycled using locally sourced soap (surfactant) and tetraoxo sulphate (VI) acid, H2SO4, producing cleaner SLO suitable for combustion in industrial burner. Recycled SLO was found to have a specific gravity of 0.8972, water content of 10%wt, carbon residue of 3.89% and a flash point of 127°C which complied with standard properties given in the literature. It can be inferred from various analyses conducted that the treatment method employed is efficient and suitable for SLO treatment.