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

This research is centered on the purification of Spent Shell Helix (HX3 20W-50) lubricating oil using acidified clay treatment with three acids options: mineral sulfuric acid (H2SO4), organic acetic acid (CH3COOH), and organic citric acid (C6H8O7), (a novel washing agent). The clay mineral, spent, purified, and fresh lubrication oil samples were characterized to determine their physicochemical properties. The clay mineral was characterized using Energy-Dispersive X-Ray Fluorescence (EDXRF). The result indicated that the clay was bentonite clay and it was successfully acidified. The result also indicated that properties of the spent lubricating oil such as Kinematic viscosities at 40 oC and 100 oC increased from 118.9 cSt and 13.9 cSt for the spent oil to 169.7 cSt and 15.2 cSt, 178.2 cSt and 16.3 cSt, 183.4 cSt and 16.8 cSt for the oil samples purified with C6H8O7, CH3COOH and H2SO4 respectively Also, the flash point increased from 106 oC for the spent oil to 133 oC, 180 oC, 189 oC for the oil samples purified with C6H8O7, CH3COOH and H2SO4 respectively. The FTIR analysis of the spent oil revealed the presence of primary oxidized products, absent in spent engine oil purified with mineral sulphuric acid (H2SO4), organic acetic acid (CH3COOH), and fresh oil. Acidified clay effectively purified the spent engine oil, bringing its physicochemical properties closer to those of fresh oil. However, the effectiveness of the treatment varied depending on the specific acid used.