Waste lubricants are those samples of oils which have become unsuitable for their intended applications. They may be recycled through the use of refining process to achieve useful products. In this work the waste lubricants were regenerated using different methods involving bleaching earth obtained from local source and activated carbon from Enugu coal as bleaching agents. The waste oil was treated with acid and the resulting mixture decanted. Bleaching of the acidic oil was conducted with the different adsorbents. The bleached oil was neutralized with hydrated lime and then filtered. The characteristic properties of the oil were analysed and the highest values were recorded for the formulation involving acetic acid/activated carbon as follows; viscosity = 169.81cst at 400C, S.G = 0.882, flash point = 1740C, pour point = -120C, water content = 1.58wt%. While the least values for the composite formulation were obtained from sulphuric acid/clay as thus; viscosity = 141.86cst at 400C, S.G = 0.866, flash point = 1650c, pour point = -160C, water content = 2.31wt%. From the results obtained, it was observed that the deviation of the service properties of the oil from the standard specifications in all the methods employed is insignificant.
Since the roman era, many liquids, including water, have been used as lubricants to minimize the friction, heat and wear between mechanical parts in contact with each other. Today, lubricating oil, or lube oil, is the most commonly used lubricant because of its wide range of possible applications. The two basic categories of lubricant are mineral and synthetic oil. Mineral oils are refined from naturally occurring petroleum or crude oil. While synthetic oils are manufactured poly-alphaolefins, which are hydrocarbon-based polyglycols or ester oils. Although, there are many types of synthetic oils, mineral oils are commonly used because of its availability and comparative advantage in terms of cost of production. In addition, it has a large body of data on their properties suitable for wide range of applications.
Lubricants are used in operation to separate moving parts in a system. They serve to protect rubbing surfaces and promote easier motion of connected parts. In the process, they carry the necessary functions of reducing friction and surface fatigue in addition to the removal of high build-up of temperature on the contacting surfaces (Udonne, 2011). At elevated temperatures of the engine oil in service, the oil will be subjected to intense degradation and subsequent reduction in properties of the oil such as viscosity, moisture content, flash point, specific gravity etc (Bakare & Udonne, 2013). Also during machine operation, the unguarded rubbing of contacting part leads to the formation of wearing out of the metal parts and deposition of dirts into the lubricating oil. In the same way, a lot of impurities are generated in the oil due to its subsequent oxidation and thermal degradation of the lubricant (Ihsa, Yusaf, & Rafat, 2013). These impurities contain unsaturates, aldehydes, phenolic compounds, alkanols, acidic compounds, and non-stable products of hydrocarbons. Other sources of contaminants include acidic fuel combustion exhaust gases and nitrogen oxides absorbed by the oil as well as dust, fuel, water, gums and other products of additive degradation. The effect of these contaminants leads to a drop in performance efficiency of a lubricant. Therefore, this oil must be removed and changed from the automobile after a few thousand kilometers of driving due to these observed stresses from serious deterioration in service. The amount of lubricating oil that is collected annually in Nigeria and elsewhere from this source is very enormous. These large amounts of waste lubricants have a significant impact on both economical and environmental aspects. If discharged into land, water or even burnt as a low grade fuel, this may cause serious distortion to the ecosystem. On the other hand, the increasing demand for lubricants and the rapid depletion of fossil fuel reserve which provides feedstock for the production of lubricating oil in Nigeria has reinforced the need to explore or adopts ways of regenerating the waste oil (Eman & Abeer, 2012). This therefore calls for aggressive approach and articulated pattern of management to ensure safe utilization and disposal if need be.
Recent advances on this recovery reveal that there are many methods available for the regeneration of waste lubricants. One of these methods involves the use of activating agent as bleaching agent. The basic principles consist of the following processes: preliminary filtration of oil to sieve out dirts and other particulates, dewatering of the residual oil, acidification, sedimentation/decantation, bleaching, neutralization, filtration, and blending to specification. This process is tailored toward obtaining high quality yield of refined lubricants that possess high quality characteristics of viscosity, flash point, pour point, specific gravity, total acid number, etc.
In this work, the regeneration of waste lubricant was carried out using different formulation involving activated clay and carbon as bleaching agents. A comparison of the performance characteristics of the refined oil with virgin base oil was investigated. The activated clay from Uzo-Uwani and activated carbon from Enugu Coal were employed in this work based on their high adsorptive capacity, as reported by Echegi & Aneke (2015), and Ibemesi & Achife (1990). This effort is further aimed at harnessing the potentials of available local raw materials towards optimization of their industrial utilization.
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