50 Atoms for Peace An International Journal, Vol. 3, No. 1, 2010 Sulphur removal from used automotive lubricating oil by ionising radiation Marcos Antonio Scapin*, Celina Lopes Duarte and Ivone Mulako Sato Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN SP) Av. Professor Lineu Prestes 2242 05508 000 São Paulo, Brazil E-mail: mascapin@ipen.br E-mail: clduarte@ipen.br E-mail: imsato@ipen.br *Corresponding author Abstract: In this work, gamma radiation was used to remove sulphur from used automotive lubricating oil. The sample was fractioned and irradiated with 10, 20, 50, 100, 200 and 500 kgy doses in a 60 Co irradiator (Gammacell-220 12 kci). Fifty percent and 70% (v/v) of MilliQ water and 30% (v/v) of hydrogen peroxide were used to improve the radiolysis. The sulphur content, before and after the irradiation, was determined by X-ray fluorescence. The results showed 68% sulphur removal at 500 kgy absorbed dose with an addition of 70% (v/v) of MilliQ water. Keywords: gamma radiation; ionising radiation; X-ray fluorescence; sulphur removal. Reference to this paper should be made as follows: Scapin, M.A., Duarte, C.L. and Sato, I.M. (2010) Sulphur removal from used automotive lubricating oil by ionising radiation, Atoms for Peace An International Journal, Vol. 3, No. 1, pp.50 55. Biographical notes: Marcos Antonio Scapin has a BSc in Chemistry and an MSc and a PhD in Nuclear Technology from the University of São Paulo, Brazil. He works on analytical chemistry and environmental chemistry using X-ray fluorescence spectrometries at Nuclear and Energy Research Institute, São Paulo (IPEN/CNEN-SP). Celina Lopes Duarte has a BSc in Pharmacy and Biochemistry, and an MSc and a PhD in Nuclear Technology from the University of São Paulo, Brazil. She is a Scientific Researcher at the Nuclear and Energy Research Institute, São Paulo (IPEN/CNEN-SP). Her research activity is on the environmental application of nuclear technology. She is an undergraduate and graduate Lecturer and Advisor. Ivone Mulako Sato has a BSc in Chemistry from the State University of São Paulo, Brazil and an MSc and a PhD in Nuclear Technology from the University of São Paulo. She held a Fellowship at KfA, Jülich, Germany in 1982 1983. She is a Scientific Researcher at the Nuclear and Energy Research Copyright 2010 Inderscience Enterprises Ltd.
Sulphur removal from used automotive lubricating oil by ionising radiation 51 Institute, São Paulo (IPEN/CNEN-SP). Her research activities are on analytical chemistry and environmental chemistry using X-ray fluorescence. She is an undergraduate and graduate Lecturer and Advisor. 1 Introduction Lubricating mineral oils are derived from petroleum and are used in automotive and industrial engines. The automotive lubricant oils require some additives, such as diethylcarbamates and sulphonate organometallic compounds, for their applications (Sychra et al., 1981). The additives act as antioxidants, dispersants and detergents. During use, the automotive lubricant oils are partially degraded, producing oxygen compounds (organic acids and ketones), high-viscosity aromatic compounds (which are potentially carcinogenic), resins and shellacs. In addition, some metallic elements are also found in the oil, derived from worn-out mechanisms or corrosion processes. The lubricating oils are not totally consumed during their use but lose their lubricating property; therefore, they should be replaced periodically according to engine specifications. In the automotive sector, the volume of used oil is large due to the great fleet of vehicles. The residues are classified as highly toxic (CETESB, 2003), thus they cannot be disposed of or reused without adequate treatment. Usually, the technologies for oil recycling employ cyclonic distillation with dehydration, flash distillation, clarification, neutralisation and filtration processes. Each step supplies some products, which receive the proper treatment. The metal removal step is important when used oils are employed as raw material to obtain other products or used as combustion materials (AMBIENTE BRASIL, 2007). The ionising radiation process has been used for different applications, especially for industrial and domestic effluent treatment (organic and biological compounds degradation and metal removal) due to its high efficiency and clean technology application (Scapin and Sato, 2002; Slegers and Tilquin, 2005; Scapin et al., 2007). In this work, gamma radiation was used to verify the sulphur removal level in used automotive lubricating oil. The hydrolysis was favoured by hydrogen peroxide and MilliQ water addition and different absorbed doses were applied. The elemental sulphur concentration was determined by X-ray fluorescence spectrometry using the Fundamental Parameters method. 2 Materials and methods 2.1 Sampling The used automotive lubricating oil sample was separated into four groups and fractioned as described below: Group A Five millilitres of the sample were transferred to three glass vials (volume: 5 ml) and named Samples A1, A2 and A3.
52 M.A. Scapin, C.L. Duarte and I.M. Sato Group B Group C Group D Four millilitres of the sample were transferred to three glass vials (volume: 5 ml) and for each one, 1 ml of hydrogen peroxide (H 2 O 2 (30%)) was added. They were mixed for 10 min in the mixer (SPEX-MIL, No. 76156) and named Samples B1, B2 and B3. Seven millilitres of the sample were transferred to four glass vials (volume: 14 ml) and each one was completed with Milli-Q water. They were mixed for 10 min in the mixer and named Samples C1, C2, C3 and C4. Four millilitres of the sample were transferred to four glass vials (volume: 14 ml) and each one was completed with Milli-Q water. They were also mixed for 10 min in the mixer and named Samples D1, D2, D3 and D4. 2.2 Processing The irradiation was performed in a 60 Co irradiator (Gammacell-220 12 kci). Groups A and B samples were irradiated with 100 and 200 kgy absorbed doses, except Samples A1 and B1, which was used as a blank sample. The Groups C and D samples were irradiated with 100, 200 and 500 kgy except for the C1 and D1 samples, which were kept as blank samples. After irradiation, the oil phase was separated by centrifugation. Wax micro powder of 2.00000 ± 0.00005 g was put into a 50 ml Pt/Au mould and then 1.00000 ± 0.00005 g of the oil sample was added. The mixture was melted on a hot plate at 60 ± 1 C, homogenised, cooled and taken out of the mould, obtaining a melted disc of 25 mm diameter and 10 mm thickness. The elemental concentration was determined by a wavelength dispersive X-ray fluorescence spectrometer (RIGAKU Co., model RIX 3000) using the Fundamental Parameters method (Lachance and Claisse, 1995). The methodology was evaluated using Standard Reference Material (SRM 1084a wear-metals in lubricating oil) from the National Institute of Standards and Technology (NIST). The results were evaluated by statistical tests recommended by EUROCHEM/CITAC Guide (2000). 3 Results and discussion The SRM 1084a data presented, as the relative standard deviation, a precision of less than 2%. The evaluation accuracy presented a Z-score value Z less than 1.0, therefore the sulphur determination method in the oil samples was validated. In Table 1, the sulphur Removal Level (%RL) for Groups A, B, C and D samples and sulphur concentration of the recycled oil sample (CRP) are shown. This sample was obtained by the current process used by oil recycling industries. The results showed a decrease in the sulphur content in all samples analysed, revealing sulphur removal by the gamma radiation process. The results are as follows: Group A samples: The best removal occurred in the A3 sample (%RL = 14%); nonlinear correlation between %RL and absorbed doses could be observed; however, greater doses provided higher sulphur removal.
Sulphur removal from used automotive lubricating oil by ionising radiation 53 Group B samples: Only the H 2 O 2 (30%) addition promoted sulphur subtraction (Sample B1: %RL = 19%). The use of greater absorbed doses (100 and 200 kgy) showed %RL = 25% and 26%, respectively; nevertheless, doses variation did not present a significant increase in the %RL value. Group C samples: The simple 50% Milli-Q water addition promoted a sulphur removal at %RL = 32% (Sample C1), but the absorbed doses increasing (100 to 500 kgy) did not produce a significant sulphur removal, the %RL value remaining at 32% to 33%. Group D samples: For 70% MilliQ water addition, the same removal level (%RL = 36) was observed for nonirradiated and 100 kgy irradiated samples, D1 and D2, respectively. A substantial deduction of sulphur content was verified for 200 and 500 kgy, where Samples D3 and D4 presented %RL = 42% and 68%, respectively. For all procedures, the results evidenced that the better condition for sulphur removal is a 70% Milli-Q water addition with 500 kgy absorbed dose. Table 1 Sulphur concentration and %RL for the A, B, C and D groups Groups Samples (µg g 1 ) (%RL) A A1 Blank 12 961 ± 70 0 A2 100 kgy 11 420 ± 62 12 A3 200 kgy 11 166 ± 61 14 B B1 H 2 O 2 (30%) 10 562 ± 58 19 B2 H 2 O 2 (30%) + 100 kgy 9705 ± 53 25 B3 H 2 O 2 (30%) + 200 kgy 9616 ± 52 26 C C1 H 2 O (50%) 8770 ± 48 32 C2 H 2 O(50%) + 100 kgy 8772 ± 48 32 C3 H 2 O(50%) + 200 kgy 8674 ± 47 33 C4 H 2 O(50%) + 500 kgy 8620 ± 47 33 D D1 H 2 O(70%) 8303 ± 45 36 D2 H 2 O(70%) + 100 kgy 8235 ± 45 36 D3 H 2 O(70%) + 200 kgy 7549 ± 41 42 D4 H 2 O(70%) + 500 kgy 4188 ± 23 68 CRP (recycled oil sample) 5495 ± 30 The sulphur removal comparison between these procedures and the current process used by oil recycling industries (Sample CRP), is shown in Figure 1. This graph shows the gradual reduction of the sulphur content along all procedures (sulphur concentration vs. sample). Sample D4 has S content at 4188 ± 23 µg g 1 and CRP sample has 5495 ± 3023 µg g 1. This result indicates a decrease of 24% in the sulphur content with the irradiation treatment.
54 M.A. Scapin, C.L. Duarte and I.M. Sato Figure 1 Proposed and conventional treatments for sulphur removal (see online version for colours) 4 Conclusion The gamma radiation process proved to be a promising treatment for sulphur removal in used automotive lubricant oils. The procedure is clean since the use of chemical agents is not necessary and does not produce secondary effluents. This fact is very important in the worldwide trend of seeking clean technologies, mainly for the used lubricating oil recycling process or for re-using applications. References AMBIENTE BRASIL (2007) Banco de dados, http://www.ambientebrasil.com.br/ composer.php3?base=residuos/index.php3&conteudo=./residuos/oleolubrificante.html (accessed 15 June 2007). CETESB (2003) Produção mais limpa, http://www.cetesb.sp.gov.br/tecnologia/producao_limpa/ casos/caso2 5.pdf (accessed 15 June 2007). EUROCHEM/CITAC Guide (2000) Quantifying Uncertainty in Analytical Measurement, 2nd ed. Lachance, G.R. and Claisse, F. (1995) Quantitative X-Ray Fluorescence Analysis Theory and Application, London: Wiley. Scapin, M.A., Duarte, C.L., Sampa, M.H.O. and Sato, I.M. (2007) Recycling of the used automotive lubricating oil by ionizing radiation process, Journal of Radiation Physics and Chemistry, Vol. 76, Nos. 11 12, pp.1899 1902. Scapin, M.A and Sato, I.M. (2002) Determination of Na, Al, Si, P, K, Ca, Fe, Co, Ni, Cu and Zn by WD-XRF spectrometry in industrial effluents after an electron-beam treatment, Avances in Analisis por Técnicas de Rayos, Vol. 11, pp.87 91.
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