Effects of Acid Types on the Recycling of used Lubricating Oil

Abstract

This study focuses on the effects of acid types on the recycling of used lubricating oil. Three different acids, H2SO4, HCl, and HNO3 were used for the treatment of used lubricating oil and subsequent neutralization of the oil with NaOH. The properties of fresh and used oil tested for were kinematic viscosity at 40 C and 100 oC, viscosity index, flash point, pour point, specific gravity at 40 oC, water content, Sulphur content, total base number (TBN), and metals present (Pb, Zn and Cu). The result obtained revealed that the quality of lubricating oil was affected after usage as a result of its property degradation and presence of heavy metals such as Pb, Zn and Cu. The result obtained shows that treatment of used oil with acids greatly improved the quality of the used oil. The extent of the recycled oil quality improvement and its yield varied with acid type. The result showed that flash point increased from 220 oC for used oil to 232 oC, 225 oC and 227 oC for oil sample recycled with H2SO4, HCl and HNO3 respectively. This is compared with 245 oC for fresh oil. Also, viscosity index increased from 91.2 for spent oil to 125,116 and 119 for oil sample recycled with H2SO4, HCl and HNO3 respectively. It was also compared with 127 for fresh oil. Sulfur content was reduced to 0.046, 0.2 and 0.35 wt% using H2SO4, HCl and HNO3 for used oil treatment. In general, based on the various analyses conducted in this study, acid treatment efficiency of used lubricant with H2SO4 is the best followed by HNO3 and HCl respectively. The use of H2SO4 also gives the highest yield of 70% recycled oil.