I am working on the adsorption of MPs and heavy metals under hydrothermal processing. Most of the adsorption kinetics I know (Pseudo-first-order, Pseudo-second-order, Langmuir, ...) use the variables of retention time and solution concentrations. I wonder if there is other kinetics using temperatures instead?
Your help is much appreciated!
Hey, @Phat Tan Vo, it depends on whether you wish to deal with isothermal kinetics or non-isothermal one. Very commonly, kinetics is studied at a fixed temperature, being isothermal. Then, when and if you will be able to determine the rate constants, you may perform isothermal kinetics at different temperatures, and, as @Raed Tareq indicated, you may obtain activation energies and everything needed to predict the effect of temperature. However, you may choose temperature as an independent variable, and characterize immediately reactions at different temperatures, introduce explicitly its effect on rate constants and use these complicated equations for fitting. Non-isothermal kinetics is often used in calorimetric studies of chemical reactions..You will need to keep in mind that pH should be controlled at different temperatures, microplastics may undergo transitions in a temperature range.
Raed Tareq Thank you for your recommendation, I will take a look at that.
Hi Mikhail Borisover, I assume my experiment belongs to a non-isothermal one. My goal is to investigate the adsorption of MPs and heavy metal with the change of temperatures, other factors such as working volume, concentration remain constant. I will first study the Arrhenius equation to see if it is suitable for my goal. It would be great if you can recommend any relevant papers in regard to this issue. Many thanks
Hi @Phat Tan Vo@, even if so, and depending on the complexity of the processes and experimental way you do that, I would be very cautious with non-isothermal kinetics. The use of formal equations will need plenty of the data across of the temperature rise. When using thermal or calorimetric methods, there are continuous scanning curves of a heat flow or mass changes vs. temperature. If adsorption is studied when continuously scanning temperature, it could be similar. However, if the effect of temperature on adsorption is determined at selecting only several (e.g., 2-5) temperatures, it will hardly be enough to go this way when the empirical kinetics is unknown. A common way to recover rate constants from adsorption kinetics measured at each temperature and applying the Arrhenius analysis would be more confident, to predict the effect of temperature
Mikhail Borisover Thank you for your explanation. I have 5 temperature conditions as you mentioned so it would be easier for me to follow the Arrhenius analysis.