Analysis of Acid Options in the Purification of Spent Motor Engine Oil using Acidified Clay

Abstract

This study focuses on the purification of spent Shell Helix lubricating oil to promote environmental sustainability and economic viability. The purification process involves the use of acidified clay treatment, utilizing three different acid options: mineral sulfuric acid, organic acetic acid, and organic citric acid (a novel washing agent). Various physiochemical properties of the clay mineral, spent lubricating oil, purified oil, and fresh lubricating oil were examined. These properties included the kinematic viscosities at 40°C and 100°C, pour point, flash point, and metal content determined through Atomic Absorption Spectrometry (AAS). The clay mineral's surface area was notably enhanced from 53.308 m²/g to 89.513 m²/g after acidification, which facilitated the purification process. The results demonstrated that certain properties of the spent lubricating oil, such as kinematic viscosities, pour point, and flash point reduced due to the presence of contaminants from prior use, while metal content increased. However, the acidified clay treatment successfully purified the spent oil, bringing its physiochemical properties closer to those of the fresh oil sample after treatment. The extent of purification, however, varied depending on the type of acid used. This research underscores the potential for sustainable management of spent lubricating oils through acidified clay treatment.