Measurements of Association and Partition Equilibria of n-Alkylbenzenes with Fulvic Acid, Humic Acid, Sodium Dodecylbenzenesulfonate, n-Dodecane, and 1-Octanol in Aqueous Media by Headspace Gas Chromatography
Date
2013-08
Authors
Eljack, Mahmoud
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Abstract
Natural organic matter (NOM) such as humic acids (HA), fulvic acids (FA), and humin in soils and sediments plays an important role in partitioning, binding, and transport of organics and metal ions in nature. We have developed an equilibrium headspace gas chromatographic (HSGC) technique and the theory to study the association and partitioning of n-alkylbenzenes (benzene, toluene, ethylbenzene, n-propylbenzene, and n-butylbenzene) with aqueous FA, HA, and sodium dodecylbenzenesulfonate (SDBS). The alkylbenzenes were chosen because they are the major constituents of gasoline and also toxic to human health and the environment. The precise measurement of n-alkylbenzenes in the vapor phase in equilibrium with the liquid phase allowed determination of solute - monomer surfactant (S), association constants (K<sub>11</sub>), solute- aggregate, S<sub>n</sub>, association constant (K<sub>n1</sub>), critical aggregation constants for FA, HA, and SDBS. It also allowed measurements of the mole fraction based partition coefficients (K<sub>x</sub>), infinite dilution activity coefficients of solute inside the aggregate pseudo-phase (γm), and the transfer free energies of alkyl chain -CH<sub>2</sub>- and benzene from aqueous to aggregate pseudo-phase. Theory shows that the parameters can be calculated without the concentration of the solute. All measurements were made at infinite dilution (<10</super>-6</super> mole fraction) where solute-solute interactions are nonexistent. Almost no such studies could be found in the literature and, therefore, constitute a fundamental contribution in this field.
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Analytical chemistry, Physical chemistry, Association and Partition Equilibria of n-Alkylbenzenes with Fulvic Acid, Humic Acid, Sodium Dodecylbenzenesulfonate, Fulvic acid, Headspace Gas Chromatography, Humic acid, Liquid Liquid Extraction, Measurements of Association and Partition Equilibria of n-Alkylbenzenes with Fulvic Acid, Humic Acid, Sodium Dodecylbenzenesulfonate, N-Dodecane, And 1-Octanol in Aqueous Media by Headspace Gas Chromatography