I am trying to study the lead ions adsorption using of natural and modified zeolite- Mordenite. I have used 0.1 g Mordenite in 20 ml of 5 and 10 ppm lead model solutions, mix for one hour (20°C and pH=5).
now I want to determination the rate constant and plotting the graph qt/t. how can I find qt ( Lead concentration in the absorbent particle).
This paper may be helpful
( Chitosan/montmorillonite composites for fast removal of methylene blue from aqueous solutions)
Materials Chemistry and Physics
https://doi.org/10.1016/j.matchemphys.2020.123236
I would avoid describing kinetic data by means of an empirical hyperbolic function, i.e. PSO. Such a description has no scientific value. I would also avoid the graphical method, where t/q is plotted against t. You will probably find R2 is close to 1, and on this basis you will conclude that "PSO is the best", but such resut might be falsified.
Nino Gagniashvili 1st you need to quantify the amount of lead (5 and 10 ppm) in 20 mL. The amount in 20 mL will be (5 or 10 mg/1000 mL)*20 mL = 0.1 and 0.2 mg, respectively. A 100% adsorption would yield a qt of (0.1 or 0.2 mg per 0.1 g modernite) = 1 and 2 mg per g, respectively on the y axis (which is qt), plotted against time. do check with others for the above calculation for confirmation.
In addition, using the so-called PSO, the value of the adsorption rate constant cannot be determined, only the value of the lumped parameter, k2, having no physical meaning. It is better to perform the kinetic test for additional Co values and try to describe the kinetic curves together using e.g. the mass balance equation based on Langmuir assumptions. Instead of k2, the rate constants ka and kd can then be determined, but also the value of qmax.
Nino Gagniashvili, If you really want to use the graphical method, then you illustrate the kinetic data for the selected Co in the t/q vs t coordinate system, and not as you misspelled q/t vs t. To these data you fit the linear function using the least squares method. Remember that the number of points close to equilibrium does not exceed the remaining points.
Mirosław Grzesik thanks a lot for your interesting answers. I will definitely consider it. I also use Langmuir and Freundlich isotherms.
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