Eliezer

Can you add some examplea of your data here, so everybody can inspect how it looks?

Provise also more details about your separation system.

Regards

G

And so it will be, if you approximate a single kinetic curve, one of these two equations. If you want to know why, take a look at some of the books on chemical reaction/reactor engineering. There you will find other forms of equations too. I would also advise comparing based on the average relative error. Regards,

Thank you very much! Soon I'll send some good data for our discussion.

The data should help. For me, at the beginning, information about the number of experimental points is enough. The important may be, for example, the insufficient number of such points or their dominace for values close to the equilibrium value. Regards,

Dear Prof. Miroslaw and Prof. Grzegorz. All my experiments are made in triplicate or quintuplicate (5 times). The adsorption data of acetylsalycilic acid are in my paper (Genesis AAS), Figure 10 and Table 5. Look at the R2 values: 0,99818 (1st order), 0,99988 (2nd order). Other work (undergraduated students-TCC Final), still not published, with adsorption of paracetamol and ASA in zeolites: look the Figure 19 a,b, pg 47 and corresponding adjustments Table 8, pg 49. Again the difference is minimal, exception for HBEA (R2=0,785). This is why I`m asking about specific models for adsorption / desorption data for drugs. Thank you for your attemption and help. I would like to hear from you soon. Prof. Eliezer

I do not think there are any equations specifically adapted to the description of sorption kinetic data for drugs. Obviously, there are other equations besides the equations used by you One can try to use the Elovich equation or combination of so called "FOM and SOM". Will you get a better fit with them than obtained in your works - I doubt it.

Now, a few words about the use of two types of functions: the exponential function and the hyperbolic function for the approximation of individual kinetic curves. Why in both cases you can get a similar, large R2 values. Both the exponential function and the hyperbolic function are functions that increase asymptotically to the limit value. The difference is that for a given value k the first one increases faster than the second one. This is confirmed by the result obtained by you and your students, where k1 is smaller than k2. The second reason is that the qt vs t shown in Figure 10 only in the range from 10 to 60 min is non-linear. In the range from 0 to 10 min, we are dealing with a linear increase, and in the range of 60 to 240 min with a constant function. In turn, the smaller R2 value for AAS-HBEA is related to the inflection point on kinetic curve. This situation is not predicted by the exponential function and hyperbolic function you use. Regards,

Thank you Prof. Mirosław Grzesik. Soon I`m going to answer. Hugs.