Abstract
The search for inexpensive and environmentally friendly alternatives for used motor oil (UMO) purification has become a topic of research. In this study, the use of bentonite clay modified by acid activation is proposed. Sulfuric acid, acetic acid (v-acid/w-clay ratio=20, 40 and 60%) and sulfuric/acetic mixtures (1:1 ratio) were used in the bentonite clay activation. The activated clays were used in the UMO treatment in a ratio of 1:4 w/v, using batch adsorption processes (contact time=12 min). To determine the structural and morphological modifications produced by the acid activation process, the clays were characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The oil clarification efficiency was quantified by UV-Vis spectroscopy, acidity, alkalinity and viscosity index. It was determined that sulfuric acid and the sulfuric/acetic activations presented a similar bentonite structure transformation, which appears in the cations leaching of intermediate layer. The treated oil with the highest clarifications (with respect to UMO) were the ones treated using bentonite activated with sulfuric acid 40 v/w% and sulfuric/acetic acid (1:1 ratio) with clarifications of 70 and 68%, respectively. The oil treated with clay activated with sulfuric acid (40%) reduced its viscosity, acidity and alkalinity by 23%, 80% and 29%, respectively.
Highlights
Motor oils play an important role in the operation and performance of a vehicle, being one of the products in greatest demand
The increasing motor oil demand combined with the decreasing petroleum availability (67 L of petroleum are required to produce 1 L of motor oil) require that used motor oil (UMO) be reused (1.6 L of UMO is necessary to obtain 1 L of motor oil)
Clay and used motor oil Bentonite clay was obtained in the city of Santa Elena and used motor oil was obtained from an oil recycling company located in the city of Quito
Summary
Motor oils play an important role in the operation and performance of a vehicle, being one of the products in greatest demand. From 1991 to recent years, the annual global demand for lubricants has remained around 35 million tons [1]. Until 2015, the growing demand from emerging markets such as Brazil, Russia, India and China have led to a 2.6% increasing in demand for lubricating oils [2]. Because of the development of new technologies and the eminent industrial and automotive market growth, it is projected that the motor oil demand increases in time. The increasing motor oil demand combined with the decreasing petroleum availability (67 L of petroleum are required to produce 1 L of motor oil) require that UMO be reused (1.6 L of UMO is necessary to obtain 1 L of motor oil). UMO needs to be purified because is considered a dangerous waste (1 gal of UMO could contaminate 1 million gallons of drinking water) due to the presence of dust, heavy metals, polycyclic aromatic compounds (PAHs), polychlorinated biphenyls (PCBs), among others [1, 3,4,5]
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