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Phosphatidylcholine - Mg2+ equilibria in a monolayer at the air/water interface

100%
Petelska A., Figaszewski Z.
Open Chemistry
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2013
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vol. 11
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issue 3
424-429
EN
Abstract The interaction between Mg2+ and a phosphatidylcholine (lecithin, L) monolayer at the air/water interface was investigated. Surface tension measurements (Langmuir method) of phosphatidylcholine monolayers as a function of Mg2+ concentration were carried out at 22°C using a Teflon trough and a Nima 9000 tensiometer. Interactions between phosphatidylcholine and Mg2+ result in significant deviations from additivity. An equilibrium theory was developed to obtain the stability constants and areas occupied by one molecule of LMg+ and L2Mg. The stability constants were K 1 = 9.95×102 m2 mol−1 and K 2 = 3.87×104 m2 mol−1. The area occupied by LMg+ is 77 Å2 molecule−1, while that occupied by L2Mg is 109 Å2 molecule−1. The Gibbs free energies of complexation for LMg+ and L2Mg are −16.91 ± 0.51 and −25.88 ± 0.76 kJ mol−1. Graphical abstract [...]
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Synthesis and monolayer film of a series of new twin-tailed gemini cationic surfactants at the air/water interface

100%
Chen Z., Feng Y., Zhou D., Zhu P., Wu D.
Open Chemistry
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2008
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vol. 6
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issue 3
477-481
EN
A series of new dimeric surfactants, twin-tailed gemini surfactants, 2(12)-s-2(12), were successfully prepared and characterized, and their monolayer films investigated by the measurement of surface pressure-area (π-A) and surface pressure-time (π-t) isotherms at the air/water interface by a Langmuir film balance. Compared to their monomeric counterparts, their collapse pressure (γcollapse) is smaller, whilst all the molecular area parameters are larger. The limited area (Alimited) and the initial area (Ainitial) of these twin-tailed gemini surfactants change with increasing spacer length s, and the surface pressure decreases with increasing time. It was also found that the higher the initial surface pressure, the larger the attenuation. [...]
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Equilibrium isotherm analysis of the sorption of congo red by palm kernel coat

86%
Oladoja N., Ololade I., Idiaghe J., Egbon E.
Open Chemistry
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2009
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vol. 7
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issue 4
760-768
EN
The ability of Palm Kernel Coat (PKC), a waste agricultural product, in the abstraction of Congo Red (CR), an anionic dye, from aqueous solution was studied. The effects of sorbent dose and temperature were studied using batch sorption system. Isotherm experiments were conducted and the data obtained were fitted with different equilibrium isotherm equations namely, Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Harkins-Jura and Halsey isotherm equations. The Langmuir isotherm equation gave the best description of the sorption process and the maximum saturated monolayer sorption capacity of the PKC for CR was 79.37 mg g−1. Harkins-Jura isotherm equation gave the poorest description of the sorption process. The linear form of the Langmuir equation was used to analyze the data obtained when the sorbent dosage was optimized by method of continuous variation. The results obtained showed that the equilibrium monolayer sorption capacity, qm, of the PKC for CR decreased (79.37–17.07 mg g−1) with an increase in sorbent dosage. The relationship between the dimensionless parameter, KR, and initial concentration, Co, showed that the sorption of CR was favored at higher initial dye concentration and PKC dosages than the lower ones. The thermodynamic parameters, such as change in the free energy, the enthalpy and the entropy, were also evaluated. The thermodynamic analysis showed that the sorption is spontaneous and exothermic. [...]
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