Quality analysis of oil recovered from used locomotive engine oil using ultrasound-assisted solvent extraction

Abstract

Herein, we present a process for recovering used locomotive engine oil using ultrasound-assisted extraction and sustainable organic solvents. We evaluated the quality of the oil recovered from used locomotive engine oil through ultrasound-assisted extraction or mechanical stirring. The extraction process involved the direct application of ultrasound (25 °C, 24 kHz, amplitude 20%) or mechanical stirring (225 rpm, 25 °C) to a mixture of used locomotive engine oil and alcoholic solvents (ethanol, propan-2-ol, 2-methlypropan-1-ol, and butan-1-ol) for 0.5, 1, and 5 min. With ultrasound (5 min), the yield of butan-1-ol was the highest (91.4 wt%), followed by that of 2-methylpropan-1-ol (79.4 wt%), propan-2-ol (12.1 wt%), and ethanol (3.6 wt%). With mechanical stirring (5 min), the yield of butan-1-ol was the highest (88.3 wt%), followed by that of 2-methylpropan-1-ol (59.8 wt%), propan-2-ol (9.54 wt%), and ethanol (2.3 wt%). The kinematic viscosities of the recovered oils extracted with 2-methylpropan-1-ol and butan-1-ol were 126.0 and 132.7 mm2 s−1, respectively, which were close to the kinematic viscosity of fresh locomotive engine oil (150.6 mm2 s−1). The recovered oil had decreased Ca, Cr, Fe, Mo, and Na concentrations. The proposed recovery is a promising approach for the support and intensification of used locomotive engine oil treatment.