EFFECTS OF ACID TYPES ON THE RECYCLING OF USED LUBRICATING OIL

Lubricant is an
oil or grease that is applied as a surface coating to moving parts to protect
and reduce friction of two surfaces in relative motion, eliminate temperature
build up and keep the engine clean (Toolingu, 2013; Udonne 2011; Ogbeide, 2010).
It also serves the purpose of transportation of foreign particles, heat
transfer, corrosion prevention, cutting of metal and protection against wear
(Udonne 2011; Ogbeide, 2010). The lubricating oils are either bio or petroleum
based and the petroleum base feedstock are mainly complex mixtures of
hydrocarbon molecules (Udonne, 2011; Hamad et
al., 2005) ranging from low viscosity oils to high viscosity lubricating
oil. T.Y chemicals (1990) analysis shows that the presence of impurities
depends on the petroleum process and production method but concluded that lube
oil contains aromatics in the range 4 to 12 % free, sulphur and other
impurities. Machineries/engines that make use of oil lubricant include all
vehicles, motor bikes, generating plants and it is also used in various
industries/factories equipments. Spent oil is any petroleum-based or synthetic
oil that has been used and as a result, is contaminated and has lost nearly all
its physical or chemical properties but do not wear out and the contaminant
present in it can be removed to the point that it can be reused as engine or
machine oil (Garthe, 2005). Contaminants or impure lubricants are drained off
from cars and disposed off as used or waste oil containing undesirable
oxidation product, sediments, metallic wear particles, water, degraded
additives and lead hazardous substances (James, 1967; Kamal and Khan, 2009;
Durrani et al., 2011; Emam and Shoaib, 2012; Abdulkareem et al., 2014).

Disposal of used
oil into the environment, used as weed killers, pouring into ditches or dumping
illegally is dangerous to life. It contaminates water as research shows that a
gallon of used oil can contaminate one million gallons of water. Used oil can
also affect plant life if poured on the ground and it sinks down into the water
table (EPA 530-F-94-008). It is therefore obvious that indiscriminate disposal
of used lubricating oil into the environment constitutes hazards to both fauna
and flora. Hence, the need to recycle used lubricating oil. There have been
several approaches in an attempt to regenerate used lubricants (Isah et al., 2013; Abdulkareem et al., 2014; Durrani et al., 2011 Jhanani and Joseph, 2011;
Ogbeide, 2010; Josiah and Ikiensikimama, 2010; Abdul-Jebbar et al., 2010; Kamal and Khan, 2009;
Rahman et al., 2008; Gorman, 2005).

Industries and
private users of lubricating oils demand necessitates the need to find ways of
regenerating  the oil after use due to
the rapid depletion of fossil fuel reserve which is the source of oil
feedstock, shortage of fresh oil, price increase and high demand (Zambiri,
1988). The increased use of lubricating oil globally for which Nigeria produces
364 166 000 litres of used oil annually disposed as a common practice into
gutters, water drains, open plots and farms which led to streams, ground water,
lakes and oceans pollution (Isah et al.,
2013; EPA 530-F-94-008). The frequent disposal of waste lubricating oils
globally is alarming and requires serious attention. Presently, many countries
in the world are presently giving serious attention to the problems of
environmental degradation and hazards caused by the disposal of waste
lubricating oils (Hamad et al., 2005;
Jilner, 1997). T.Y Chemicals (1990) referred regeneration of used lubricating
oil as the means of removal of contaminants or impurities by sulphonating
agents such as sulphuric acid, oleum or sulphur trioxide and concluded that the
process is made up of two cycles, the removal of about 80 % aromatics and other
impurities in the first cycle and other 20% impurities in the second operation
cycle. However, Isah et al. (2013)
carried out regeneration of used engine oil treated with sulphuric acid and
bleached using industrial bleaching earth and activated carbon for different
formulated grades. The results obtained by the group showed that the best grade
in comparison with fresh oil in terms of viscosity, specific gravity and total
acid number was obtained using industrial bleaching earth. Abdulkareem et al. (2014) compared the performance
efficiency of used lubricating oil treatment methods and concluded from their
findings that acid and acid/clay treatment methods were the most attractive
with consequences of environmental pollution resulting from acid sludge. Emam
and Shoaib (2012) also made comparison between acid/clay percolation and
solvent/clay methods of recycling lubricating oils and concluded that the used
of acid treatment method  was the most
attractive interms of quality while solvent method gave the highest yield.

The used of
sulphonating agents specifically sulphuric acid to treat used lubricant has
been fully established by many researchers (Abdulkareem et al., 2014; Isah et al.,
2013; Emam and Shoaib, 2012) and its performance has been very competitive but
environmental consequences are part of its major limitations. In addition to
environmental consequences, there is a dare need to quantitatively and
qualitatively analyze the effect of other acids which suggest in this study the
investigation of nitric, sulphuric and hydrochloric acids suitability and
effects in the treatment stage of used lubricating oil recycling.