ABSTRACT
The present work deals with the extraction and pre-concentration of nickel (II) ions using emulsified liquid membrane (ELM) in the presence of di- (2-ethylhexyl) phosphoric acid (D2EHPA) as an extractant. The emulsion stability was achieved by the biodegradable surfactants Triton X-100 addition diluted in kerosene. Influence of operating conditions that affect ELM performance were investigated. A comparative study between the optimization parameters of this process was carried out both experimentally and with the Response Surface Methodology (RSM), in accordance with the Box-Behnken matrix. The following parameters were investegated: D2EHPA / Triton X-100 ratio between 0.5 and 3.5, initial concentration of the feed phase between 200 and 500â ppm and pH of the feed phase from 2.5-10. The transport of Ni (II) ions was evaluated according to the extraction yield as an analytical response and the optimal conditions were determined. It was found that the calculated values being in good agreement with experimental data that under the optimized conditions ([Ni] = 350â¯ppm, Vagitation = 200â¯rpm, t = 20â¯min and pH = 6.6), Ni (II) ions extraction was recorded more than 94% of efficiency.
Subject(s)
Research Design , Surface-Active Agents , Ions , Polyethylene GlycolsABSTRACT
Algerian crude oil displays a marked propensity for asphaltene precipitation, leading to solid deposits during extraction, transportation, and storage. The relationship between precipitation and chemical composition is unclear; in fact, Algerian crude oil actually features a low asphaltene concentration, despite its relatively large rate of deposit formation. The rationalization of the precipitation process and its remediation should benefit from a molecular characterization of the crude oil. In this study, two unstable asphaltene fractions (A1 and A2) from two different deposits, and two resin crude oil fractions (R1 and R2) from the Hassi-Messaoud Algerian field have been characterized at the molecular level by means of high-resolution mass spectrometry with an Atmospheric Pressure Chemical Ionization (APCI) source. Positively and negatively charged compounds with molecular weights 200-1200 m/z were detected. Several thousand molecular stoichiometries were identified and classified for each sample, in terms of heteroatom content and aromaticity, searching for trends characteristic of the two asphaltenes and of the associated resins. The A2 asphaltene, from a downstream storage tank, displays a higher aromaticity and O-heteroatom content, which correlates with an enhanced aggregation propensity, in comparison to the A1 fraction, collected at the well bore. The resin fractions are found to be abundant in aliphatic hydrocarbons and heteroatomic compounds of moderate aromaticity. The more polar resin fraction, R2, is enriched in N-containing species, with respect to the less polar resin fraction R1, which correlates with the stabilizing function observed in previous works. The results stress the view of crude oil fractions as complex mixtures, rather than in terms of average prototypical compounds, when facing the understanding of asphaltene deposition conditions.
ABSTRACT
The addition of nucleophilic imines, using 2-hydroxybenzophenone as a chemical auxiliary, is presented. An intramolecular six-membered ring via hydrogen bonding that enhances the reactivity and selectivity is the key of this strategy, which is supported by DFT calculations and experimental trials.
ABSTRACT
In this communication, a new photocatalytic strategy for the addition of alkyl-radical derivatives to N-sulfinimines with complete diastereoselectivity and moderate to good yields is presented. This is the first asymmetric photocatalytic addition to N-sulfinimines under visible light irradiation with smooth conditions and functional group tolerance.
