Cation Exchange Capacity (CEC) of montmorillonite (the calculation)

[yijing84]

I am going to modified the pristine montmorillonite (MMT) by using cationic surfactant.
However I am confusing on the way to calculate the weight of the surfactant.
I have been searching hundred of journals but couldn't get any information on how to calculate it.
For example:

MaterialsThe commercial sodium montmorillonite (Cloisite®Na) used in the present study was supplied by Southern Clay Products, Gonzales, Texas (USA). The cation exchange capacity (CEC) of montmorillonite (MMT) is 92.6 mequiv/100 g as reported by suppliers. The basal spacing of MMT is 12.1 Å. This MMT was used as such without any further purification. Various amines used as cationic surfactant.

Organoclay preparation and characterizationThe required amount of amine (taken as twice the amount required based on CEC of MMT) based on 2.5 g of Cloisite®Na was protonated in 100 ml of 1 N HCl for 1 h at room temperature with vigorous stirring to obtain the ammonium chloride salt.

However, they do not state that how to calculate the required amount of amine based on CEC??
Anyone can help me out in this?
Thank you so much in advance.

 

[chemisttree]

Cation exchange capacity is calculated using an ammonium salt. If your surfactant can occupy the anionic sites as easily as ammonium ion, then calculate the amount of surfactant using its formula wt. This example of montmorillonite's CEC is 92.6 milliequivalents per 100g of dry clay. Your amine surfactant is very likely to be less efficient at exchange than the much smaller, more mobile ammonium ion. It is left to you to determine your clay's "surfactant" exchange capacity. The CEC will be the upper bound to what is possible. Also, it takes time for larger species to intercalate into the clay so that factor is also left for you to consider. Google "surfactant pillared clays" to see what others have reported.

 

[yijing84]

I had gone through many literature but I still can't figure out how to calculate the amount of surfactant needed.Can anyone show me the calculation please?
My head is going to blow-up because of this...
Thank you so much.

 

[chemisttree]

... based on 2.5 g of Cloisite®Na was protonated in 100 ml of 1 N HCl for 1 h at room temperature...

See here? Your sample size is 2.5 grams. How much amine for such a small sample?

Well, if you chose to use a 100 gram sample, and the CEC of the MMC is 92.6 meq/100 grams, and the instructions tell you to use twice that amount of amine...


Can you take it from here?

 

[LudusRex]

Dear researcher,

Thank you for your question. I understand your confusion regarding the calculation of the weight of the surfactant for the modification of montmorillonite. To determine the required amount of amine based on the cation exchange capacity (CEC) of montmorillonite, you can use the following equation:

Required amount of amine (g) = CEC of montmorillonite (mequiv/100 g) x Weight of montmorillonite (g) x 2

In this equation, the CEC of montmorillonite (mequiv/100 g) is the value provided by the supplier, which in this case is 92.6 mequiv/100 g. The weight of montmorillonite (g) is the amount of Cloisite®Na used, which in this study is 2.5 g.

For example, if we use the equation with the given values:

Required amount of amine (g) = 92.6 mequiv/100 g x 2.5 g x 2 = 463 mequiv

This means that for 2.5 g of Cloisite®Na, you would need 463 mequiv of amine to fully modify the montmorillonite.

I hope this helps clarify the calculation for you. It is important to note that the amount of amine required may vary depending on the type of amine used and the desired level of modification. It is always recommended to conduct a preliminary study to determine the optimal amount of amine needed for your specific experiment.

Best of luck with your research.

Sincerely,