LEVELS OF CONTAMINANTS IN USED MOTOR OIL AND THEIR POTENTIAL EFFECT ON THE ENVIRONMENT

ABSTRACT

Motor oil used by internal combustion engines requires replacement over a period due to contamination that affects its lubricating functions. The used motor oil finally ends up in the environment, whose physicochemical compositions are unknown to determine the impact. This thesis contains information concerning the environmental impact associated with used motor oil. Some of the various ways by which it enters the environment were reviewed. The physicochemical properties (heavy metals, volatile aromatic hydrocarbons, total petroleum hydrocarbons, H₂S, density, specific gravity, water content, viscosity, pour point, flash point, soot content, and colour), determined by collecting ten used motor oil samples each from private and commercial vehicles and two samples of fresh motor oil for petrol and diesel engines using the American Standard for Testing Measurement (ASTM) are as described. The results showed that the used oils recorded high levels of contaminants above the EPA maximum permissible limit for waste oils. Again the commercial vehicles recorded high levels of contaminants in the used oils than the private vehicles. It can be concluded that motor oils have significant amount of harmful substances and metals, and therefore must be treated to reduce these contaminants levels before they are reused or final disposal into the environment.

CHAPTER ONE

1.0 INTRODUCTION

1.1 Background Information

Motor oil is suitable for use in engine crankcase. It can also be used to lubricate electric motors. It is used to lubricate various parts of internal combustion engines as well as the moving parts (Klamman, 1984) to reduce friction, prevent corrosion, dissipate heat, and hold in suspension the micrometer-sized by-products of engine wear, combustion (soot) and oil degradation products (Ritter, 2013).

Motor oil is about 90% paraffinic hydrocarbon base stock distilled from crude oil, with the remainder constituting the "additives package" (Bachelder, 2006). The additives package may differ depending on the manufacturer, but they are mostly detergent inhibitor package and viscosity index improvers (Nehal, 2011). There are two major categories of base oils and these are mineral base oil and synthetic base oil (Magnante, 2002). The mineral base oils are made from crude oil (IARC, 1984) while the synthetic base oils are chemically synthesized (Magnante, 2002; Randles, et al., 2007). The mixture of these two base oils in certain proportions produces semi-synthetic motor oil (Jackson, 1987; Mobile 1, 2005). There are standards for motor oil set by the Society of Automobile Engineers (SAE) based on viscosity (SAE, 1999); which allows motor oil to be graded as single-grade (i.e. cannot use Polymeric Viscosity Index Improvers), and multi-grade (i.e. can use Polymeric Viscosity Index Improvers).

There are various brands of motor oils, and the basic differences are the base oils and the additives used by the manufacturers (Klamann, 1984) which determine the quality.

The quality of mineral base oils depends on the composition of the original crude oil and the refining processes while that of synthetic base oil is based on the ability of the formulator (synthetic chemist) to chemically synthesize selected molecular structures at targeted specifications to obtain the desired properties (Jackson, et al., 1987). Specific additives, depending on the brand and the application are also selected based on the molecular structure of the base oil and other properties such as thermal and oxidation stability, traction, volatility, viscosity, pressure, shear strength, flash point and pour point (Hentschel, 1985). Additives such as rust and corrosions inhibitors, anti-wear and extreme pressure (anti-seize or anti-scuffing), antioxidants, dispersants, detergents are meant to serve various purposes in the motor oil but their compositions may differ with respect to the brand. For instance, rust inhibitors are designed to reduce oxidation and neutralize acids (Nehal, 2011). They have high polar attraction toward metal surfaces (Rizvi, 2009; Leslie, 2003) and interact with the metal surface to form obstinate, continuous film that prevents water from reaching the metal surface. Organosulfur and organo-phosphorus compounds are usually used as anti-wear and extreme pressure (anti-seize or anti-scuffing) additives (Leslie, 2003). The type and number of chemicals used as additives also comes with cost (Jackson, et al., 1987), which could influence the quality of the brands.

However, synthetic motor oils are meant to meet needs that mineral motor oils cannot. They do not have undesirable weak links inherent in conventional mineral oils that break down in extreme heat and congeal in extreme cold (Mobil, 2005), and are therefore meant for high performance engines with extreme operating temperatures.

In the process of normal use, motor oil gets contaminated with impurities such as dirt, products of combustion, wear metals from engine parts, fuel, and toxic chemicals (based on chemical composition of additives as well as molecular structure of base stock) (Roy, 1997).

These contaminants usually darken the motor oil (Scott, 2005). The additives breakdown and the oil become deteriorated loosing its lubricity (Livingstone, et al., 2009). However, the used oil finally ends up in soil, air and water by escape and loss of oil during engine operation, application on rural roads for dust suppression, asphalting with asphalt containing oil, and indiscriminate disposal or landfill (Rafael, 1988) and cause pollution.

1.2 Statement of the Problem

Motor oil used by internal combustion engines requires replacement over a period due to contamination (Elena and Pichtel, 2004), which affects its lubricating functions (Livingstone, et al., 2009). Some of these contaminants include products of combustion, engine wear, dirt, and fuel (Roy, 1997). The used motor oil removed from vehicles is finally released into the environment, whose physicochemical composition is unknown. Studies have shown that used motor oil is a source of oil contamination of waterways (USEPA, 2003; Sander, 2009). It has the potential to contaminate soil (Abdulsalam, et al., 2012), and also release volatile organic compounds as well as combustion products into the atmosphere and cause undesirable conditions (Hopmans, 1974; Rafael, 1988).

1.3 Main Objective

To assess the physicochemical properties of used crankcase lubricating oil from private and commercial vehicles in Tema, Ghana.

1.4 Specific Objectives

To measure the physical properties such as density, specific gravity, water content, viscosity, pour point, flash point, soot content, and colour of used motor oil.

To measure levels of heavy metals (Pb, Ba, Cr, Cd, Zn, Fe, Cu, Ni, V, As and Mn), volatile aromatic hydrocarbons (benzene, ethyl benzene, toluene and xylene - BTEX), total petroleum hydrocarbons (TPH), and hydrogen sulfide.

1.5 Justification

The rampant indiscriminate disposal and re-use of used motor oil across the country has necessitated a study on the physicochemical characters of used motor oil in other to assess its potential impact on the environment; to enable stakeholders and policymakers to make informed decisions to address the problem which could be harmful to biota.

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Item Type: Ghanaian Topic  |  Size: 94 pages  |  Chapters: 1-5

Format: MS Word  |  Delivery: Within 30Mins.

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