|کد مقاله||کد نشریه||سال انتشار||مقاله انگلیسی||ترجمه فارسی||نسخه تمام متن|
|5746209||1618787||2017||9 صفحه PDF||سفارش دهید||دانلود رایگان|
- UPLC-IM-TOFMS was able to identify OyS-NAs from Ox-NAs.
- Dissociation constants were estimated for individual and total NA species from OSPW.
- The pKa decreases with increasing n andÂ âZ numbers for O2, O3, O4, and O2S species.
- The pKa values were 3.3 for O2, 4.4 for O3, 7.3 for O4, and 4.1 for O2S species.
- The pKa value was 3.9 for total NAs.
Ultra-performance liquid chromatography ion mobility time-of-flight mass spectrometry (UPLC-IM-TOFMS) was utilized for the analysis of naphthenic acids (NAs) in fractions of pH-dependent sequential liquid-liquid extractions from oil sands process-affected water. Ion-mobility separation technique allowed the differentiation of OySâNAs (2Â â¤Â yÂ â¤Â 4) from OxâNAs (2Â â¤Â xÂ â¤Â 5) via drift time versus retention time separations. The results indicated that the addition of S atom to the O2âNA molecule led to a lower increase in the dissociation constant (pKa) compared to that caused by the addition of O atom. Because additional O is present as OH while the S atom is present as the CSC structure, the latter does not involve into the deprotonation process directly. The pKa value decreased along with increasing carbon number and |Z| number for O2â, O3â, O4â, and O2SâNA species, except for O5â, O3Sâ, and O4SâNA species, each of which are comprised of chemical structures with distinct functional groups. A calculation model was developed to estimate pKa values for individual and total NA species via nonlinear regression curve fitting, utilizing the relative abundances of detected NA species. pKa values were calculated as 3.9 for total NAs, 3.3 for O2âNAs, 4.4 for O3âNAs, 7.3 for O4âNAs, and 4.1 for O2SâNAs. Knowledge of NAs pKa is crucially important for the comprehensive understanding of their potential transformation route and toxicity as well as for the development of water remediation applications. Both the ion-mobility separation technique and the new calculation model could be widely applied for the investigation of other complicated pollutants present in water and wastewater.
Journal: Chemosphere - Volume 184, October 2017, Pages 738-746