Hello,
I want to describe my adsorption kinetic results by using intraparticle diffusion model “IPD” of Weber and Morris.
The plots of qt versus t1/2 at different initial phenol concentrations show multilinearity characterizations (Figure is attached), indicating that two steps occurred in the adsorption process.
According to (Li et al., 2012) who obtained similar results, the first sharp section is the external surface adsorption or instantaneous adsorption stage. The second portion is attributed to the gradual adsorption stage, where intraparticle diffusion is rate-controlled.
My first question is why (Li et al., 2012) attributed the second step to intraparticle diffusion, despite their plot shows that equilibrium is reached during this step (dqt/dt =0).
my second question is why we don't consider the step between time=0 and (time at the first qt ) this will give us a plot with three steps.
Thank you.
Li, Y., Du, Q., Liu, T., Sun, J., Jiao, Y., Xia, Y., ... & Wu, D. (2012). Equilibrium, kinetic and thermodynamic studies on the adsorption of phenol onto graphene.Materials Research Bulletin, 47(8), 1898-1904.
Dear Salim,
Maybe you'll find the answers in our earlier paper, here attached.
Not all published papers present correct things, unfortunately.
Alain
Dear Salim,
Maybe you'll find the answers in our earlier paper, here attached.
Not all published papers present correct things, unfortunately.
Alain
Dear Salim,
Like Alain said, not all published manuscript have correct information. You can also go through the attached papers, I hope you find them helpful.
Kind regards.
Paul
Dear Salim
I am not familiar with the article by Weber & Morris, but the plot only shows 2 periods. The time from t=0 to the first experimental point includes the first rapid initial coverage, the experimental points with slope up to about t=20-25 are the interpreted as due to intraparticle diffusion. The subsequent points show that the particle is full.
This type of adsorption has been used as a cheap way of roughly estimating surface area where the y intercept is (roughly) proportional to area.
Dear Salim,
In my opinion, the plot shown is wrongly plotted and hence, wrongly interpreted. It should start from t=0 as you said, then the first line would represent rapid transfer of adsorbate onto the adsorbent surface by physical/chemical forces, the second one, the rate determining step (which is shown to be first by Li et al 2012) actually represent adsorption due to IPD and third portion (which is second one in the graph by Li et al 2012) shows saturation of adsorbent surface.
You may find more details on interpretation of results derived from Weber-Morris model for adsorption in my two papers, noted below.
1. N.S. Randhawa, N.N. Das, R.K. Jana, Adsorptive remediation of Cu(II) and Cd(II) contaminated water using manganese nodule leaching residue, Vol. 52, Iss. 22-24, pages 4197-4211, 2014
2. N.S. Randhawa, D. Dwivedi, S. Prajapati, R.K. Jana, Application of manganese nodules leaching residue for adsorption of nickel(II) ions from aqueous solution, International Journal of Environmental Science and Technology, 2013-12-10, http://dx.doi.org/10.1007/s13762-013-0460-4
Contact me if don't find full papers.
Regards,
Dear all
I want to thank all the researchers who have supported my idea, this will be helpful when writing my PhD thesis.
Dear all.
I am currently correcting my thesis on adsorption work. I found that this discussion might be useful for my thesis, and my knowledge.
I would like to have the full papers from Prof Randhawa, as my institution does not subscribe the journal currently. Thank you.
Dear all,
May I know that the value of intraparticle diffusion rate constant (k1) for first region should higher than second region (k2)?
In my experimental case, the intraparticle diffusion shows this type of curve along with the graph. Please suggest me that if there are three or two type of diffusion in one graph possible, then what type of diffusion in my graph shows.
Dear Shanti maam,
in your graph 3 plot s are possible by taking two two points each . Your diffusion shows multi-particle diffusion
Thank you, Sehaspreet Kaur Toor, for the valuable answer to clear my doubt.
Dear salim,
The attachment (your study) shows twin linearity not multiple linearity. As such it may not be perfectly compared to that of Li et al (2012). Secondly, i think the attribution of the study by Li et al 2012 to intraparticle diffusion despite equilibrium reached was because their intraparticle diffusion parameter values Kid signified that intraparticle diffusion is the most dominant.. Such conclusions can be deduced from important model parameters like Kid .
lastly, we dont consider the curve from time 0 to because studies like this is better judged after breakthrough has been achieved. Therefore, it is preferable to start marking linearity after breakthrough time has been attained.
Dear all,
Regarding the multi-linearity graph plot of Intra-particle diffusion, may I know how to decide the range for each segment?
Is it solely based on observation?
Thanks.
Dear all
I have also the same question asked by Nor Adilla Rashidi. How can we decide that how many linear stages should be there? Only on observation or some fundamental concept is there?
I found an interesting paper (see below) which details the method of applying Piecewise linear regression to analyze adsorption data instead of visually determining multi-linear stages
Malash, G. F., & El-Khaiary, M. I. (2010). Piecewise linear regression: A statistical method for the analysis of experimental adsorption data by the intraparticle-diffusion models. Chemical Engineering Journal, 163(3), 256-263.
Hope this helps!
Refer to sections 2.4, 3.0,3.1 and 3,2 of our current paper for detailed explanation on this. Kindly find the paper attached.
Diffusion mechanism and Article Diffusion mechanism and effect of mass transfer limitation d...
effect of mass transfer limitation during the adsorption of CO2 by polyaspartamide in a packed-bed unit.- Badges
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