Can anyone help me to calculate the reaction rate constantc for catalytic degradation of dye? How to know whether reaction follows pseudo-first order kinetics or not?
Hi Nilofar,
When you mention "catalytic degradation of dye", are you refering to enzyme catalyzed degradation? The reason I ask the above question is because, in an enzyme catalyzed reaction, there are two distinct events that are involved. The first step is the binding of the dye to the enzyme to form the enzyme-dye complex ( see scheme below) and the second step is the catalysis whereby the dye is degraded to yield the catalytically competent enzyme and the dye-degradation product. The rate constants involved in the reaction are as shown below
k1 k2
[Enz] + [Dye] [Enz-Dye]--------------->[Enz] + [degraded dye]
k-1
The velocity or rate of the reaction is k2[Enzyme-Dye] and is a first-order rate. However, I realize that your question pertains to "rate constants" and not the "rates". Since there are 3 distinct rate constants (k-1 and k2 are first order rate constants with units of time-1 and k1 is a second order rate constant with units of time-1concentration-1), the answer to your question would depend on what event are you interested in depending on whether you are talking about an enzyme-catalyzed dye degradation. I hope the response helps!
Thank you sir for the answer. My question is concerned with catalytic degradation of dye in presence nanoparticles.
In case of nanoparticle-mediated catalysis, I may not be the best person to answer your query given my lack of exposure in that. Thanks!
The degradation of the dye may be taking place on the active surface of the nanoparticles which serve as a catalyst.. Such surface catalysed reactions show 3 orders of reaction depending on the amount of substrate in this case the dye.
1) At low concentrations of the substrate , the order is one and the first order rate constant (k)is given by the equation,
k=1/t . ln [initial concentration]/{concentration at time t]
k is obtained from the first order plot of the lnCo/Ct ie k=slope
2)At high concentrations of substrate the order is zero as the rate becomes independent of substrate concentration as the surface of the solid catalyst is fully covered with the substrate and no further adsorption of substrate can take place. The rate constant is given by the equation ,k= dc/dt where dc is the amount of substrate reacting in time dt
3) At moderate concentrations of the substrate ,the order is a fraction
It appears that your reaction takes place at low concentration hence the order will be one
Pseudo first order reactions involve the participation of two reactants but one is in excess compared to the other. The rate of reaction depends only on the concentration of the reactant present in small amount. So, though the reaction is bimolecular, it obeys first order kinetics. Hence the term pseudo first order kinetics.
Please contact me if there is some doubt
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Yurii V Geletii
Emory University
Your question does not have an answer because you did not provide any details.
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Ali Farhat
GHD Pty Ltd
If I were you, I would present my data of "C vs time", where C is the dye concentration and plot it in first order (as ln (C/Co) vs time) and also as second order "(1/C) - (1/Co) vs time" and compare their linear regression by plotting the linear trendline. Also try zero order which can also be possible.
Force it through zero (y-intercept=0) and add equation and R-squared value.
If R^2 from the linear regression exceeds 0.90, it follows the pseudo-first order kinetics
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Ahmed I. Osman
Queen's University Belfast
Hi
Can you please find the attached image that shows the equation I used during the calculation of reaction rate of conversion of butene
Have a very good day and best of luck
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Mirosław Grzesik
Insitute of Chemical Enginering Polish Academy of Sciences
Dye degradation is usually a multi-step process. One can, of course, try to describe the change in dye concentration over time by means of an exponential equation corresponding to the first order chemical reaction, but the constant k obtained on this basis will have no physical meaning. This is a so-called lumped parameter that takes into account the impact of many different factors. But to design a process in a reactor, that's enough. Regards,
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Karthigaimuthu Dharmalingam
Periyar University
https://www.khanacademy.org/science/chemistry/chem-kinetics/copy-of-kinetics/v/plotting-data-for-a-first-order-reaction
This link will be useful to find the rate constant for first order reaction. Thank you.
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Mirosław Grzesik
Insitute of Chemical Enginering Polish Academy of Sciences
In the case of single chemical reactions, the lack of dependence of the degree of conversion on the initial substrate concentration proves that the reaction is of the first order.
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D. V. Prabhu
Wilson College, Mumbai
The rate constant (k) of a first order reaction is independent of the initial concentration of the reactant.
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Mirosław Grzesik
Insitute of Chemical Enginering Polish Academy of Sciences
The rate constant of any order chemical reactions does not depend on the initial concentration of the given substrate. This is an inherent feature of the rate constant of the chemical reaction having an order. Of course, this does not apply to the various so-called pseudo-rate constants.
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