Inline fluoride measurement - ISE probes might not be an option

[Annelissenc.]

Hello, me again

If you wanted to put Probe in a tank to read Fluoride Ion in a continuous circulation which kind of choices you would go for??

1 - ISE electrodes are not an option as I've been told they are more like analytical solutions and they work well in static baths, we have a changing over time solution so constant calibration would be an issue and the material in these probes would not last.
2 - The sample line runts between 51-55C in a continuous circulation
3 - The line has a mix of phosphoric acid - 4%, HF- 0-2%, increasing aluminum in solution up to 60,000ppm ad water.
4 - Conductive conductivity probes are good to reared the overall water bath concentration that has been demonstrated corelates with the H3PO4 concentration, but we still need the Fluoride concentration value which these probes don't read.

we are designing the sample loop to be continuous circulation so we hopefully avoid deposits, but struggling with solutions to read the in line HF concentrations

HELP!!

 

[pierreick]

Hi,
You may go for a specific electrode. Check with Mettler Toledo or another big name.

https://www.mt.com/int/en/home/prod...MIuLHclPmF_QIVnL9LBR31HgWrEAAYASAAEgI7I_D_BwE

Pierre

 

[Annelissenc.]

Pierreick

I've done that, no solution from them...only offline probes for that specification...

 

[pierreick]

Hi,
What about Raman?

https://pubmed.ncbi.nlm.nih.gov/29136913/

Pierre

 

[EdStainless]

We always did Fl offline. When we were busy it meant daily sample and test.
The probes are crazy delicate and have very special storage requirements.
Using them destroys them.
We could measure the other acids and metals all in line, but not Fl.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Annelissenc.]

pierreick (Chemical)8 Feb 23 12:45
Hi,

can you explain in more detail... this Roman?? I cant open the article

 

[hacksaw]

try

https://www.mt.com

there are other methods if you have serious money, but rarely justified.

 

[georgeverghese]

The first pre treatment step would be to drop the temp to say 10degC below the max operating saturation solubility temp for AlF3, I would imagine, so that AlF3 doesnt scale everything it touches in the concentration sensor unit. From Google, AlF3 solubility drops with increasing temp, (which explains why AlF3 scales the relatively warmer inner tank).

 

[pierreick]

Hi,
About Raman spectroscopy check with Mettler. Thís could be an option to follow the chemical reaction. Google should be your ultimate resource.
I do believe taking sample time to time and using a specific electrode could be the answer instead of using inline probe (if any), your current cycle time being long enough.

Good luck
Pierre