I did adsorption test and the data I have is the initial concentration and final concentration after adsorption.
How to use this data in the adsorption isotherm?
Please I need steps because this is my first time.
My article can be helpful: Article Opportunities and constraints of using the innovative adsorb...
Freundlich Adsorption Isotherm
In 1909, German scientist Freundlich provided an empirical relationship between the amount of gas adsorbed by a unit mass of solid adsorbent and pressure at a particular temperature. It is expressed using the following equation –
x/m = k.P1/n (n > 1)
where ‘x’ is the mass of the gas adsorbed on mass ‘m’ of the adsorbent at pressure ‘P’. ‘k’ and ‘n’ are constants that depend on the nature of the adsorbent and the gas at a particular temperature.
The mass of the gas adsorbed per gram of the adsorbent is plotted against pressure in the form of a curve to show the relationship. Here, at a fixed pressure, physical adsorption decreases with increase in temperature. The curves reach saturation at high pressure. Now, if you take the log of the above equation –
log x/m = log k + 1/n log P
To test the validity of Freundlich isotherm, we can plot log x/m on the y-axis and log P on the x-axis. If the plot shows a straight line, then the Freundlich isotherm is valid, otherwise, it is not. The slope of the straight line gives the value of 1/n, while the intercept on the y-axis gives the value of log k.
You can use CAVS - adsorption evaluation to perform all regressions (Kinetcis, Isotherm and Fixed-bed).
The program uses non-linear regression, which is far more better than linear regression, and the equations are ready to be use.
The software is FREE to be used.
check the software here: http://bit.ly/CAVS_tutorials
The Langmuir isotherm model is solved by plotting Ce/qe on y-axis and Ce on x-axis. The slope will give the value of 1/qm and intercept will give 1/(kl *qm).
In the Freundlich model, we plot log qe on y-axis and log Ce on x-axis. The slope will give 1/n where n is adsorption intensity and intercept will give log kf, where kf is model constant.
If you have "final concentrations" that can be treated as equilibrium concentrations (it is worth checking it out), then you have enough information to describe the data using empirical functions - but only empirical ones. However, I would not advise to draw any conclusions based on such description.
First of all, one should avoid the use of graphical methods and R2 calculation for equilibrium data in nonlinearly transformed coordinate systems and straight lines fitted to such data. Unfortunately, such an approach, often falsifying the results, is proposed in the above software.