Hello,
I'm using the Freundlich isotherm for fitting data of an activated carbon adsorption. When fitting the data, the Kf is different when starting from a concentration unity of µg/L and mg/L. The difference is not just the factor 1000.
Can anyone help to declare this difference? Or are there any 'rule' which say you can only use the Freunlich isotherm whit data in mg/l?
Thank in advance!
Dear Jolien,
It mybe due to application of logarithmic function in your calculations.
Are you fitting by linear or non-linear regression? In the former case, are you seeing a difference that could be due to linearization using log(...) versus ln(...) (or vice-versa)?
Linearization of the isotherm equation eliminates (0, 0) as a robust point in the data set. So, in case you are linearizing to fit, are you seeing a difference because the weighting skews to the higher concentration range as you rescale the data?
Finally, the Freundlich isotherm has concentration to a factor 1/n. Have you worked through the theoretical implications of this as far as how rescaling your concentration by x1000 will rescale K by 1000^(1/n)?
Please take the concentration unit in mg/L or µg/L, and no rule is bound to use only the mg/L unit. If you take the concentration unit in µg/L, then the value of Kf will be in [(μg / g) / (μg / L) ^ 1 / n].
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