Dear all,
I am currently working on the non-linear adsorption isotherm using SOLVER-add in in Microsoft Excel. May I know what is the basis to estimate/guess the initial value for the isotherm constant?
Your help is highly appreciated.
Thank you!
Actually, it depends of the model you are using.
If you are using the classic Langmuir model [q = qs * b * p / (1 + b * p)], a good initial value will be your maximum adsorbed amount for qs. For the b, divide the slope of the isotherm at the origin (= Henry coefficient) by qs.
The problem is not so complex; if you part from the Langmuir equation: Vads/Vm = KAPA /(1+ KAPA)
applying the inverse of this equation, and rearrange we can obtain the linear transform:
PA/Vads = 1/(vmKA) + PA / Vm,
from the linear form of the Langmuir equation, you can plot PA/Vads vs PA, and finally from the slope and intercept can be determined Vm and KA respectively.
Most isotherms models you can linearize.
What isotherm model are you using?
Dear all,
I'm currently working on 3-parameters isotherm model i.e. Sips, Redlich-Peterson, etc. Thus, they cannot be solved using a linear method. In order to solve with non-linear function, I need to guess the initial value. Therefore, I would like to know how to decide on initial value, since different initial value results in difficult outcomes.
Your assistance is truly appreciated. Thanks.
- Badges
- Science topic