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Surfactants are chemical compounds that decrease the surface tension or interfacial tension between two liquids, a liquid and a gas, or a liquid and a solid. The word "surfactant" is a blend of surf ace- act ive a ge nt , [ 1 ] coined in 1950. [ 2 ]
Upon introducing surfactants (or any surface active materials) into a system, they will initially partition into the interface, reducing the system free energy by: [citation needed] lowering the energy of the interface (calculated as area times surface tension), and; removing the hydrophobic parts of the surfactant from contact with water.
γ is surface tension of the mixture; γ 0 is surface tension of pure water; R is ideal gas constant 8.31 J/(mol*K) T is temperature in K; ω is cross-sectional area of the surfactant molecules at the surface; The surface tension of pure water is dependent on temperature. At room temperature (298 K), it is equal to 71.97 mN/m [4]
Surface tension is an important factor in the phenomenon of capillarity. Surface tension has the dimension of force per unit length, or of energy per unit area. [4] The two are equivalent, but when referring to energy per unit of area, it is common to use the term surface energy, which is a more general term in the sense that it applies also to ...
This means that the surfactant adsorbs at low surfactant concentrations with its head-group contacting the surface. Depending on the type of head-group and surface, the attraction will have a short-range contribution for both non-ionic and ionic surfactants. Ionic surfactants will also experience a generic electrostatic interaction.
During this process, surface tension decrease as function of time and finally approach the equilibrium surface tension (σ equilibrium). [3] Such a process is illustrated in figure 1. (Image was reproduced from reference) [2] Figure 1: Migration of surfactant molecules and change of surface tension (σ t1 > σ t2 > σ equilibrium).
Surfactin, like other surfactants, affects the surface tension of liquids in which it is dissolved. It can lower the water's surface tension from 72 mN/m to 27 mN/m at concentrations as low as 20 μM. [9]
Toggle the table of contents. ... Surface tension: CMC. 8.04×10 −5 M at 21 ... and Kotilen-20) is a polysorbate-type nonionic surfactant formed by the ethoxylation ...