213 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) ISSN (Print) 2313-4410, ISSN (Online) 2313-4402 Β© Global Society of Scientific Research and Researchers http://asrjetsjournal.org/ Determination of Trace Metals in Crude Oils by Atomic Absorption Spectrophotometry in Khurmala and Guwayar Oil Fields of Kurdistan Region, Iraq Saima Jadoona*, Abdulfattah Ahmad Aminb, Hawbash Khaleel Mahmoodc, Dalyia Akram Hamoodid, Mohammed Fatih Mohammed Sabire a,d,eDepartment of Natural Resources Engineering and Management, Universityof Kurdistan-Hewler, Erbil, 4401, Iraq. bErbil Technology Institute. Erbil Polytechnic University, Kurdistan, Iraq. cMinistry of Natural Resources, Erbil4401,Iraq. aEmail:Saima.jadoon@ukh.krd.edu bEmail:abdulfattah14ahmad@yahoo.com cEmail:hawbashkhalil@yahoo.com dEmail:d.hamoodi@ukh.krd.edu eEmail: m.fatih@ukh.edu.krd Abstract Fifteen crude oil samples were collected from different oil fields of the Kurdistan region, Northern Iraq to determine four trace metals, Fe, Ni, Cr and Pb. The analytical technique is applied mainly by flame atomic absorption spectrophotometry (ASS). Samples of these areas has not been previously examined for trace elements contents. API value of crude oils are inversely proportional to specific gravities and might be considered as a primary estimation for hydrocarbon contents. The relationship between trace metals and American Petroleum Institute (API) values of the samples are inversely proportional where the increasing API value of crude oil samples means a decrease in the metal contents of the samples. The method of dry ashing- acid dissolution (DA) was implemented. The results concluded that crude oil samples of the Kurdistan region have a low metal content. Nevertheless, they could be seen as an essential health hazard for humans and the environment. In t-Test 𝑑𝑑𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠˂ 𝑑𝑑𝑐𝑐𝑐𝑐𝑠𝑠𝑐𝑐𝑐𝑐𝑠𝑠𝑐𝑐 for iron, chromium and lead, there is no relationship between these three heavy metals. ------------------------------------------------------------------------ * Corresponding author. http://asrjetsjournal.org/ American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 20, No 1, pp 213-223 214 Keywords: crude oil; API; Specific gravity; Atomic Absorption. 1. Introduction Crude oils are basically a complex mixture of organic and inorganic matters, presenting trace elements that can be grouped under inorganic compound categories [1]. The significance of determining trace elements that exist in crude oils is helpful for further information about exploration, production and the refining process. Heterogeneous distribution of trace metals in crude oils could be applied to further explain the geochemical characterization of the basin and source rocks [2]. Hitchon and Filby stated that crude oils can be classified based on the trace metal content which exists in similar litho-stratigraphic situations into families [3]. There is a marine pollution problem in different origins where trace elements can be used to differentiate between the crude oils, according to an environmental site assessment, those locations which have been contaminated by oil products are viewed as the extension of pollution [4]. Crude oils can be classified in terms of trace metals as heavy, medium, light and residual fraction [5]. Refining heavy crude oil requires more expenditure in comparison to light crude oil because of the high level of metal content, the high cost is related to either hydrogen addition or yield loss due to carbon rejection [6]. Selecting a reliable method for this process is a vital step. There are several methods for the determination of trace elements in crude oil by such neutron activation [1,7], pulse polarography [3], proton induced X-ray emission [8], high performance liquid chromatography [9], atomic absorption spectrophotometry, ASS [10] and Induced coupled plasma emission ( ICP) [11]. The ICP is not be available in many laboratories due to the requirements and cost. Furthermore, most of the methods for overcoming these problems come with organic injection by the nebulization system [12], Electro thermal vaporization [13] and Improving of sample treatments [14]. ASS is the analytical technique for this process regarding its availability, simplicity and cost of instrumentation requirements. Bettinelli and Tittarelli,[15], identified a comparison for the determination of trace elements in crude oil between flame atomic absorption and other instrumental techniques and achieved that accuracy, repeatability, reproducibility and precision of the flame direct method have progressed compared to other data given by the Institute of Petroleum (IP) 228 method. Procedures for the atomization system were clarified as the introductory for the crude oil samples [10,16,18]. Barbooti and his colleagues [20], stated that silica gel can be used for lubricating oils as a stabilizer during reference and acid digestion for determining trace metals. Udoh and his colleagues [21], recommended using the procedure of p-xylene sulphonic acid ashing for the purpose of mineralizing crude oil samples in order to analyze for Fe, Cu, Ca, Na, Ni, Mg, and Zn. The advantage of this method is the prevention of the loss of materials during ashing. Osuji & Onojake, [18], applied the method of dithionite citrate carbonate for the pre extraction of Pb, Fe, Ni, Cr, and V and analyzing all metals by ASS in order to solve the matrix problem. Kowalewska, [22] , discovered that chemical modifiers like Pd could be vital in determining Ni in crude oils by ASS while it is introduced to a muffle furnace as a sample. Dittert and his colleagues [23], said continuum source radiation has been applied for continuous determining Cr and Fe in crude oil samples continuously by American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 20, No 1, pp 213-223 215 atomic absorption and preliminary treatment for samples involve homogenization in an ultrasonic bath. Sedykh and his colleagues [24], applied that autoclave digestion that consists of nitric acid and hydrogen peroxide and the procedure was applicable for V and Ni contents. Ortega and his colleagues [25], examined microwave digestion that works based a maximum temperature and pressure system (ranging from 220oC and 40 bar to ~1400˚C and 80 bar) by making a comparison with a digestion method in the High Pressure Asher (HPA-S) autoclave. They concluded that digestion improvement, increasing sample size and detection of a limit occurs, if pressure and temperature are increased. The objective of this work is to determine Fe, Cr, Ni and Pb in some newly explored oil fields of the Kurdistan region in Northern Iraq. In addition the correlation of the results with other basic characteristics of crude oil such as API and specific gravities. Moreover, evaluating the experimental procedures that have been applied for the samples by ASS was reviewed. 2. Materials and Methods 2.1. Apparatus This experiment was implemented on a Buck 210 VGP atomic absorption spectrophotometer and set at the conditions referred to in Table 1. The specific gravity, API, value which stands for American Petroleum Institute were found out by the hydrometer method (PM-B-4) and its values are shown in Table 2. 2.2. Materials Muffle furnace12000oC 240V, hot plate stirrer and hood were provided by the KRG. AAS instrument and its standard solution, 1000 Β΅g.mL-1 were provided by the University of Kurdistan-Hewler. Fifteen samples of crude oil were collected from different oil fields of the Kurdistan region, Iraq. 2.3. Procedures 2.3.1. Dry Ashing Acid Dissolution (DA Method) Specific amount of crude oil samples 1-3g were weighed in a porcelain crucibles accurately and were heated the samples on a hot plate at ~130oC for 4-5 hours. After that sulfuric acid 1-3g was added into the crucibles then waited to perform the charring at 180oC. The samples became an ash in a muffle furnace at 550oC for 6 hours. Hydrochloric acid, 5ml was added into the ash and transferred into calibrated flask for the purpose of dilution with deionized water. 3. Results and Discussion 3.1. Results Trace metal contents were determined by the calibration curve method (CC Method) and achieved accurate and precise results. This method is applied only when there is a linear relationship between absorbance (y) and concentration (x). Finally, the unknown concentration of the element is calculated from the calibration curve by interpolation. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 20, No 1, pp 213-223 216 Table 1: Operating Parameter for Flame Atomic Absorption Spectrophotometer. Table 2: API, Specific gravity of crude oil samples in different oil fields. Figure 1: This graph shows the concentration of trace metals in each sample. 3.2. Discussion API follows the American Petroleum Institute, which refers to set standards for petroleum products. One of the significance of API standard is the method of measuring the density of petroleum. Despite of classifying oils into light, medium, heavy and extra heavy. Elements Parameter Flame Type Lamp Current, mA Wavelength, nm Background Correction Fe Air/Acetylene 7 248.3 yes Pb Air/Acetylene 2 283.3 yes Ni Air/Acetylene 4 232 yes Cr Air/Acetylene 4 357.9 yes Sample No Field Names Sp.gr at room temp. ASTM D1298 Sp.gr at 15.56oC ASTM D1298 API, ASTM 1 Taqtaq 0.781 0.7835 49.09 2 Garmiyan 0.833 0.8353 37.89 3 Guwayer 0.855 0.8625 32.55 4 Khurmala 0.851 0.8535 34.2 5 Khurmala,1 0.898 0.9008 25.58 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 20, No 1, pp 213-223 217 β€’ Light > 31 β€’ Medium is between 22 and 31 β€’ Heavy < 22 β€’ Extra heavy < 10 However, specific gravity is the comparison of the density between one substance and another that is used as a standard reference, mostly water. Light oil β€œless dense” is much more preferable than dark oil β€œmore dense” because it contains a huge amount of hydrocarbons which can be converted into gasoline. API gravity of oil is found by using this formula: API gravity = (141.5/Specific Gravity) – 131.5 at 69 Fβ—¦. The relationship between API gravity and relative density of the oils is inversely proportional, which means the higher API gravity of the oils the less density. Figure 2: This graph shows the concentration of trace metals in each sample. Figure 3: This graph shows the concentration of trace metals in each sample. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 20, No 1, pp 213-223 218 Figure 4: This graph shows the concentration of trace metals in all samples. Table 3: Mean, Standard deviation of Iron, Chromium and Lead Table 4: Correlation table between Iron, Chromium and Lead. In the above correlation table of iron, chromium and lead, it shows that there is a weak relationship between these three metals. In table 6 since 𝑑𝑑𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 <𝑑𝑑𝑐𝑐𝑐𝑐𝑠𝑠𝑐𝑐𝑐𝑐𝑠𝑠𝑐𝑐 , we are 95% confident that there is strong evidence and we are rejecting null hypothesis that there is no relationship between lead and iron. In table 6 since 𝑑𝑑𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 <𝑑𝑑𝑐𝑐𝑐𝑐𝑠𝑠𝑐𝑐𝑐𝑐𝑠𝑠𝑐𝑐 , we are 95% confident that there is strong evidence and we are rejecting hypothesis that there is no relationship between chromium and iron. In table 7 since 𝑑𝑑𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠< 𝑑𝑑𝑐𝑐𝑐𝑐𝑠𝑠𝑐𝑐𝑐𝑐𝑠𝑠𝑐𝑐 , we are 95% confident that there is strong evidence and we are rejecting null hypothesis that there is no relationship between chromium and lead. # Fe Pb Cr 1 0.36747 10.8997 0.16787 2 0.65815 7.00574 0.69061 3 0.8907 9.54874 0.69061 4 0.8035 11.3488 0.95199 5 0.74536 7.87989 8.7932 Mean 0.69304 9.33657 2.25886 SD 0.17957 1.67882 3.27709 VAR 0.0403 3.52303 13.4241 Fe Pb Cr Fe 1 Pb -0.159 1 Cr 0.21175 -0.4397 1 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 20, No 1, pp 213-223 219 Table 5: t-Test of Iron and Lead Assuming Unequal Variances. Table 6: t-Test: of Iron and Chromium Assuming Unequal Variances. Table 7: t-Test of Lead and Chromium Assuming Unequal Variances 4. Conclusion From this work, we conclude that the crude oil which is present in the Khurmala and Guwayar oil fields are of Fe Pb Mean 0.693036 9.3365743 Variance 0.04030465 3.5230333 Observations 5 5 Hypothesized Mean Difference 0 df 4 t Stat -10.238776 P(T<=t) one-tail 0.00025645 t Critical one-tail 2.13184679 P(T<=t) two-tail 0.0005129 t Critical two-tail 2.77644511 Cr Fe Mean 2.258856 0.69304 Variance 13.42414 0.0403 Observations 5 5 Hypothesized Mean Difference 0 df 4 t Stat 0.954185 P(T<=t) one-tail 0.197012 t Critical one-tail 2.131847 P(T<=t) two-tail 0.394024 t Critical two-tail 2.776445 Pb Cr Mean 9.3365743 2.258856 Variance 3.5230333 13.424141 Observations 5 5 Hypothesized Mean Difference 0 df 4 t Stat 3.8444094 P(T<=t) one-tail 0.0042576 t Critical one-tail 1.9431803 P(T<=t) two-tail 0.0085151 t Critical two-tail 2.4469119 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 20, No 1, pp 213-223 220 good quality after measuring samples from both oil fields. The research was done by evaluating the heavy metals and proved the relationship between trace metals and API values of the samples are inversely proportional while increasing API value of crude oil samples means a decrease in the metal contents of the samples. The method of dry ashing- acid dissolution was implemented. The results concluded that crude oil samples of the Kurdistan region have low metal contents. We are 95% confident that there is strong evidence to reject null hypothesis and there is no relationship between chromium, iron and lead. 5. Recommendation In the recent years, significant development has been achieved in Kurdistan region and this leads to the region to depend only on the oil. Dealing with oil either exporting or importing to any country is the most effective way to pollute the environment. This prosperous region has owned numerous amounts of natural gas and crude oils. The Oil industry has referred to series of operation from exploring to marketing via pipeline and tankers. These oil industries are a source of toxic gas and those which carries sulfur which is the main factor of cancer and disease. Of course, the environmental issue could be considered very well. Social awareness has enabled people to protect themselves from those areas that oil companies are busy with oil operations especially those company which refined the crude oils into its products. New technology has invented modern equipment and interested much more in determining trace metals in crude oils. However, those oil companies which are currently working in Kurdistan region should import and apply that equipment which is less harmful to environment because excessive remaining of oil industries in one place has a serious influence on the civilian. Kurdistan Regional Government should provide the oil companies an outline regarding oil operation in Kurdistan region and the way that could be acceptable for people. Acknowledgement I would like deeply thank to University of Kurdistan-helwer for helping me to finish my research project. Reference [1] J. Sainbayar, D. Monkhoobor and B. Avid, "Determination of Trace Elements in the Tamsagbulag and Tagaan Els Crude Oils and Their Distillation Fractions Using by ICP-OES," Advances in Chemical Engineering and Science, pp. 113-117, 2012. [2] J. Alrich, A. hilner and H. Stark, "Distribution of trace elements in crude oils from Southren Germany," Chemical Geology, vol. 48, 1985. [3] B. Hitchon and R. H. Filby, "use of trace elements for classification of crude oils into families, examples from Alberta, Canada," American Association of Petroleum and Geologists (AAPG), pp. 838-849, 1984. [4] M. M. Barbooti, M. A. Al-Taee and B. H. Qasim, "Electrothermal atomic absorption spectrophotometric determination of V, Ni and Pb in hydrocarbons polluted Soils," Engineer, Technol, American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 20, No 1, pp 213-223 221 vol. 28, pp. 17-28 , 2010. [5] M. M. Barbooti, S. H. Al-Madfai and D. A. Al-Sammerrai, "Thermogravimetric characterization of Quayarah heavy crude oils," Journal of Thermal Analysis, vol. 31, pp. 253-260, 1986. [6] J. G. Reynolds, "Removal of Nickel and Vanadium from Heavy Crude Oils by Echange Reaction," Americal Chemical Society, Divisions of fuel Chemistry , vol. 49, pp. 79-80, 2004. [7] C. Chifang, D. Zhuguo, F. Jiamo and S. Guoying , "Determination of Trace Elements in Crude Oils and Organic Materials Extracted from Oil-forming Source ROcks in China By INAA," Journla of Radioanalytical and Nuclear Chemistry , vol. 151, pp. 177- 184, 2005. [8] H. J. Fischbeck, M. H. Engel , A. V. Ruffel and B. L. Weaver, "Applications of an External Beam PIXE Method for Determining the Distribution of Trace Metals In Degraded and Nondegraded Crude oils," Nuclear Intruments and Methods in Physics Research, vol. 24, pp. 655-657. [9] F. Tadayon, A. Massoumi and A. Eslami, "etermination of Vanadium, Nickel, and Iron in Crude Oil by High-Performance Liquid Chromatography," Journal of Chromatographic Science, vol. 37, pp. 371- 374, 1999. [10] G. Sebor, I. Lang, P. Vavrecka, V. Sychra and O. Weisser, "The Determination of Metals in Petroleum Samples by Atomic Absorption Spectrometry, Part 1, The determination of Vanadium," Analytica Chemica Acta, vol. 78, pp. 99-106, 1975. [11] R. I. Botto, "Matrix Interferences in the Analysis of Organic Solutions by Inductively Coupled Plasma- Atomic Emission Spectrometry," Spectrochemica Acta Part B, vol. 42, pp. 181-199, 1987. [12] S. Dreyfus, C. Pecheyan, C. Magnier, A. Prinzhofer and C. P. Liennemam, "Direct Trace and Ultra- Trace Metals Determination in Crude Oil and Fractions by Inductively Coupled Plasma Mass Spectrometry.," Journal of ASTM International, vol. 2, pp. 1-8, 2005. [13] T. Saint Pierre, L. F. Dias and R. Q. Aucelio, "Determination of Cu, Mn, Ni and Sn in Gasoline by Electrothermal Vaporization Inductively Coupled Plasma Mass Spectrometry, and Emulsion Sample Introduction," Spectrochemica Acta Part B, vol. 57, pp. 1991-2001, 2002. [14] R. M. De Souza, R. M. Silveria and R. Q. Aucelio, "Determination of Refractory Elements in Used Lubricating Oil by ICP-OES Employing Emulsified Sample Introduction and Calibration with Inorganic Standards," Analytical Aciences, vol. 20, pp. 351-355, 2005. [15] M. Bettinelli and P. Tillarelli, "Evaluation and Validation of Instrumental Procedures for the Determination of Nickel and Vanadium in Fuel Oils," Journal of Analytical Atomic Spectrometry, vol. 9, pp. 805-812, 1994. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 20, No 1, pp 213-223 222 [16] M. M. Barbooti and F. Jasim, "Electrothermal Atomic Absorption Spectrometric Determination of Vanadium," Talanta, 1982. [17] J. L. Fabec and M. L. Rushak, "Determination of Nickel, Vanadium, and Sulfur in Crudes and Heavy Crude Fractions by Inductively Coupled Argon Plasma/Atomic Emission Spectrometry and Flame Photometry," Analytical Chemistry , vol. 57, pp. 1853-1863. [18] L. C. Osuji and C. M. Onojake, "Trace Heavy Metals Associated with Crude Oil: A Case Study of Ebocha-8 Oil-Spill-Polluted Site in Niger Delta, Nigeria," Chemistry & Biodevirsity , vol. 1, pp. 1708- 1715, 2004. [19] G. P. Brandao, R. C. De Campus and H. C. DE Jesus, "Determination of Copper, Iron and Vanadium in Petroleum by Direct Sampling Electrothermal Atomic Absorption Spectrpmetry," Spectrochemica Acta Parrt B,, vol. 62, pp. 962-969, 2007. [20] M. M. Barbooti, N. S. Zaki, Baha-Uddin and E. B. Hassan, "Use of Silica Gel in the Preparation of used lubricating Oils for the determination of Wear Metals by Flame Atomic Absorption Spectrophotometry," Analyst (London), vol. 115, pp. 1059-1061, 1990. [21] A. P. Udoh, A. A. Thomas and E. J. Ekanem, "Application of p-Xylenesulphonic Acid as Ashing Reagent in the Determination of Trace Metals in Crude Oil," Talanta, vol. 39, pp. 1591-1595, 1992. [22] Z. Kowalewska, "Effect of Chemical Modification on Behavior of Various Organic Vanadium Forms during Analysis by Electrothermal Atomic Absorption Spectrometry," Spectrachemica Acta Part B, vol. 62, pp. 273-283, 2007. [23] I. M. Dittert, J. S. Silva, R. G. Araujo, B. Welz and H. Becker-ros, "Direct and Simultaneous Determination of Cr and Fe in Crude Oil Using High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry," Spectrochemica Acta Part B, vol. 64, pp. 437-543, 2009. [24] E. M. Sedykh, L. N. Bannykh, G. S. Korobeinik and N. P. Starshinova, "Determination of Nickel and Vanadium in Crude Oils by Electrothermal Atomic Absorption Spectrometry and Inductively Coupled Plasma Atomic Emission Spectroscopy after Mineralization in an Autoclave," inorganic Materials, vol. 47, pp. 1539-1543, 2011. [25] G. S. Ortega, C. Pecheyran, G. Hudin, E. Marosits and O. F. Donard , "Different Approaches of Crude Oil Mineralisation for Trace Metal Analysis by ICPMS," Microchemical Journal, vol. 106, pp. 250- 254, 2013. [26] Institute of Petroleum, "Standard Methods of Analysis and Testing of Petroleum and Related Products," London, vol. 2, p. 336, 1989. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 20, No 1, pp 213-223 223 [27] Institute of Petroleum, "Standard Methods of Analysis and Testing of Petroleum and Related Products," London, vol. 1, p. 160, 1989. [28] N. S. Zaki, M. M. Barbooti, S. S. Baha-Uddin and E. B. Hassan, "Determination of Trace Metals and Their Distribution in Heavy Crude Oil Distillates (350˚C+) by Atomic Absorption Spectrophotometry," Applied Spectroscopy, vol. 43, pp. 1257-1259, 1989. [29] M. F. Ali, A. Bukhari and M. Saleem, "Trace Metals in Crude Oils from Saudi Arabia," Industrial & Engineering Chemistry Product Research and Development, vol. 22, pp. 691-694, 1983. [30] R. F. Must, R. R. Ruch and W. F. Meents, "Vanadium in Devonian, Silurian, and Ordovician Crude Oils of Illinois," Illinois State Geological Survey, p. 483, 1973. [31] R. M. Carlson, M. M. Pena , M. M. Boduszynski, C. E. Rechsteiner, A. S. Shafizadeh and P. C. Henshaw, "Geochemical-Viscosity Correlations among Heavy Crude Oils of the San Joaquin Valley," California, Paper 1998- 2003, 7th UNITAR Heavy Crude and Tar Sands International Conference Proceedings., pp. 1998-2003, 1998. [32] M. M. Barbooti, E. Z. Said, E. B. Hassan and S. M. Abdul-Ridha, "Separation and Spectrophotometric Investigations of the Distribution on Nickel and Vandium in Heavy Crude Oils," Fuel, vol. 68, pp. 84- 87, 1989. [33] G. Sebor, V. Kubelka and O. Weisser, "Separation and Characterization of Vanadylporphyrins from Romashkino Petroleum," Collection of Czechoslovak Chemical Communications, vol. 44, pp. 551-557, 1979. [34] C. P. Lienmann, S. Dreyfus, C. Pecheyran and O. F. Donard, "Trace Metal Analysis in Petroleum Products: Sample Introduction Evaluation in ICP-OES and Comparison with ICP-MS Approach," Oil & Gas Science and Technology, vol. 62, pp. 69-77, 2007.