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| Freundlich Adsorption Isotherm |
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| This type of isotherm is described by the equation |
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| where K and n are the parameters of the equation which depend on the nature of the gas, and P is the pressure. |
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| At equilibrium, pressure Ps, x/m reaches its maximum value, that is, no further adsorption takes place even if the pressure is increased. A saturation state has been achieved. The adsorption isotherm which conforms to Freundlich equation is shown in below figure. |
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| fig 7.3 - Freundlich adsorption isotherm |
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| Since n is greater than one, qualitatively, it can be said that the extent of adsorption x/m does not increase rapidly with increase in pressure as shown in the above figure. Freundlich equation can be transformed into a linear form by taking the logarithms on both sides of the equation 1. |
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| Hence, if the plot of log(x/m) versus log P yields a straight line, it implies that the adsorption process conforms with Freundlich isotherm. From the intercept, the parameter K is obtained, while the slope is equal to (1/n). |
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