In the kinetics study, the value of R2 for pseudo second order is obtained as 0.992 but the calculated qe value did not obtain close to experimental value. While for pseudo first order, R2 is obtained as 0.975 and calculated qe fits well with experimental value. How can I justify these data for which kinetic model is the best fir for such case?
There are other regression methods besides R2. Maybe in one of those methods, the PFO model will come out better than the PSO model. so that both the experimental data and the model fit degree overlap
You may have to use a different Error model (least squares, reduced chi squared...) for the justification of the model as R2 is only suitable for linear regressions (which you may not used for the adsorption kinetics?) Have a look in to the literature: John R. Taylor, "An Introduction to Error Analysis" (2nd ed., 1997)
Christoph Hahn I used both cases namely linear and non linear model for PFO and PSO. In both cases, R2 is higher for PSO but calculated Qe is more closer to PFO. Here, I am giving my closer data for non linear as an example. Initial concentration, Co = 50 mg/L, time, t= 10-100 min, adsorbent dose = 20 mg, volume = 100 ml. equilibrium time was 90 min, where Qexp =190 mg/g.
In PSO, R2=0.993, Qe= 235 mg/g
In PFO, R2 = 0.97, Qe = 190.2
How to justify this data? Linear case also similar.
Adsorbent dosage, 20 mg, is too low. While weighing, the % error is high and almost all of the solution remains in the environment. Since the solution concentration changes little, the qt value changes a lot in case of possible fluctuations when measuring
Mehmet Can Dal Here I have attached the plot for Cu adsorption. Please find the attached.
Dear Dharma; the dots on the plotcontinue to rise, indicating that you finished the experiment early without reaching equilibrium. If it were me, I would determine the moment of equilibrium with a preliminary experiment. In conclusion, I can say that; the graph shows that if you continued the study of adsorption kinetics, you would most likely reach your point of qt=qe=210 mgg-1