Evaluation of Extraction Induced by Emulsion Breaking for Ni and V Extraction from Off-Shore Brazilian Crude Oils

Abstract

This work reports a study on the evaluation of extraction induced by emulsion breaking (EIEB) for Ni and V extraction from crude oil. Graphite furnace atomic absorption spectrometry (GF AAS) was employed for the determination of the analytes in the extracts. The extraction procedure was based on the preparation of oil-in-water emulsions, by mixing the crude oil with the aqueous extractant solution containing HNO 3 and Triton X-114 as surfactant, which were subsequently broken by heating. After emulsion breaking, two phases were formed: a top phase containing the original crude oil sample and a bottom phase, which was the aqueous extract containing the extracted Ni and V. The aqueous phase was collected, appropriately diluted, and analyzed by GF AAS for the determination of Ni and V in the extracts and subsequent calculation of extraction efficiency. The extraction procedure was first studied using water-in-ol emulsion; the best extraction conditions were achieved with 2.5 g of sample (about 3 mL) emulsified in 1 mL of extraction solution containing 6.5 mol L −1 of nitric acid and 20% (m/v) of Triton X-114. However, the extraction efficiency was only about 10% for Ni and V. The influence of the sample/ extractant volume ratio showed that sample volume lower than 3 mL resulted in higher extraction efficiency for both analytes, highlighting the use of oil-in-water emulsion to increase Ni and V extraction efficiency. Maximum extraction of Ni and V was obtained when the crude oil (approximately 0.3 g) was diluted with 2.5 mL of mineral oil free of metals. The diluted sample was emulsified by vigorous manual agitation with 3 mL of an extractant solution containing 20% (m/v) Triton X-114 and 6.5 mol L −1 HNO 3 . The emulsion breaking was induced by heating at 90 °C for 40 min, followed by centrifugation at 5000 rpm for 15 min. The EIEB procedure was applied to five crude oil samples, and the extraction efficiency was accessed from the total concentration of Ni and V in the samples determined by direct analysis by GF AAS and ICP-MS. The optimized EIEB procedure provided extraction of 82−103% of the Ni contained in the tested samples and 50−74% of the V.

Ionic liquid assisted extraction induced by emulsion breaking for extraction of trace metals in diesel, gasoline and kerosene prior to ICP-OES analysis

“…It is important to note that the limit of detection (LOD) was chosen as one of the figures used to assess the merits of the ILA-EIEB, since it is an analytical parameter that is closely related to sensitivity. The proposed ILA-EIEB method showed 2.68, 0.03, 8.74 and 1.399 μg/L LODs for Ba, Na, Ni and V, respctively, which were quite comparable with literature reported studies [ [10] , [32] , [37] , [43] , [44] , [45] ]. Furthermore, the newly developed ILA-EIEB method was accurate (80-101) and precise (1.9-4.7) for all the invesigated metals (Ba, Na, Ni and V).…”

“…Moreover, Table S1 illustrate acceptable percentage recoveries of up to 100 ± 6 % for Ba, Na, and Ni and 85.4 % for V. The low recoveries for V are due to the inability of the proposed ILA-EIEB to extract +5-oxidation state (VO 3 − ) of V from the organic matrix. [ 10 ]. The three significant parameters (concentrations of HNO 3 , Triton X-100, and ionic liquid) were further optimised by using BBD and 0.1 g sample mass was selected to be optimum.…”

“…The recoveries for V were then compared with other literature reports. For example, a study reported by de Sousa and co-workers investigated the use of EIEB for the determination of Ni and V by GF-AAS in off-shore Brazilian crude oils and very low recoveries (50-74%) of V ranging were obtained [ 10 ]. Additionally, a t -test confirmed that V cannot be extracted quantitatively from the crude oil samples using the EIEB procedure.…”

“…It is worthy to indicate that, several studies have reported on EIEB, where high volumes of carcinogenic organic solvents (xylene and hexane) and concentrated corrosive acids (HNO 3 and HCl) were used, making the extraction environmentally unfriendly [ 35 , [43] , [46] , [47] ]. It was also noted that, the extraction of V was challenging, and these shortcomings were reported in literature, where extraction effeciencies of 50–74% were obtained [ 10 ]. However, the proposed ILA-EIEB showed an improved extraction efficiency (80%) of V in in fuel oils.…”

“…It is reported that human exposure to these metals is associated with several health challenges such as liver and kidney damage (Zn, Pb, Co and Cu), carcinogenic cells (As, Cd and Ni), female infertility (Sb) and neurotoxic dysfunctionality (Co, Hg, Cr and Pb) [ [6] , [7] , [8] , [9] ]. Metals like V and Ni degrade the quality of the oil, thereby affect the value negatively [ 10 ]. Due to the detrimental effects of the metals in fuel oils, there is a need to develop trustworthy and effective methods for the determination of concentration levels of metals in fuel oil for monitoring and awareness purposes.…”