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Liquid solid adsorption equilibrium and adsorption isotherm

The mechanism of liquid-phase adsorption complex than gas adsorption, adsorption properties of organic compounds on a large number of studies have shown that:

     (1) of the same family sequence the greater the molecular weight organic compounds, the higher the adsorption capacity;
     (2) the solubility of small hydrophobic high degree of adsorption is easy;
     (3) general aromatic compounds more easily than the adsorption of aliphatic compounds;
     (4) chain compounds known compounds more easily than the side-chain adsorption.

Adsorption isotherm equation

     Used to describe the adsorption isotherm type of mathematics known as the adsorption isotherm equation

Isotherm 1.Langmuir

     Monolayer Langmuir isotherm: qe = aqmpe / (1 + ape)
     Where, qm-absorption over the surface adsorbate monolayer adsorption capacity was, kg (adsorbate) / kg (adsorbent);
     pe-a balance of adsorbate pressure, Pa;
     a-absorption coefficient.

     Georgia Muir formula commonly used in liquid-phase adsorption, it is also written in the following forms:
     qe = aqmye / (1 + a'ye)
     Where, a '- absorption coefficient;
     ye-adsorbate in a liquid phase equilibrium concentration, mole fraction.
     Langmuir relationship is an ideal formula may adsorption, which represents the uniformity of the surface between the adsorbed molecules do not interact with each other under a single molecular layer adsorption, when the law of balance.

Isotherm 2.Freundlich

     For isothermal cases, the adsorption heat with coverage (ie, adsorption capacity) was increased, showing a decrease of the number of adsorption equilibrium, Freundlich the following formula:
     qe = kpe1 / n or qe = k'ye1 / n
     - Where, k, k'-Freundlich adsorption coefficient
     n-and a constant temperature is generally believed that n = 2 ~ 10 when the absorption process easy; n <0.5 when the adsorption process of embarrassment.
     Freundlich-type is stable, such as empirical formula, applicable to low concentration of gas or the concentration of the unknown components of the solution was adsorbed.