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phosphoric acid purification

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bulentce:
i would like to know how can we remove iron and heavy metals from phosphoric acid ?

thanks

eugenedakin:
Hello bulentce,

After a quick search, there were two methods of industrial production of phosphoric acid, Thermal Phosphoric Acid Method, and Wet Phosphoric Acid Method.

Here are some details on the two methods:


--- Quote ---Thermal phosphoric acid: This very pure phosphoric acid is obtained by burning elemental phosphorus to produce phosphorus pentoxide and dissolving the product in dilute phosphoric acid. This is the cleanest way of producing phosphoric acid, since most impurities present in the rock have been removed when extracting Phosphorus from the rock in a furnace. The end result is food grade, thermal phosphoric acid; however, for critical applications additional processing to remove arsenic compounds may be needed.

Wet phosphoric acid: Green phosphoric acid is prepared by adding sulphuric acid to calcium phosphate rock, or slurry. The reaction for calcium phosphate slurry is:
3H2SO4(aq) + Ca3(PO4)2(aq) + 6H2O(l) ↔ 2H3PO4(aq) + 3CaSO4(aq)+ 6H2O(l)

Through modern filtering techniques the wet process acid can be cleaned up significantly but still isn't as pure as thermal phosphoric acid; as it may contain other acidic species such as hydrofluoric acid.
--- End quote ---

If the phosphoric acid is originally created by the Thermal Method (for food grade quality), you may want to try a cation exchanger.  I am not sure if this would work given large volumes of phosphoric acid, or high levels of iron contamination, but it may be worth a try to determine the economics from a laboratory simulation-size sample.

I wish you the best.

Sincerely,

Eugene

bulentce:
Eugene thank for information.

we have 20% phosphoric acid has 200 ppm iron.

i am trying to find a company n internet  who is specialized acid purification but i cant find.

do you know any company that can install IX plant for this application.

our customer kas 200 tons/day p205.

thanks again

bulent

eugenedakin:
Hi bulentce,

I am not familiar with companies that specialize in phosphoric acid purification.  A quick google search revealed this company:

http://www.encyclopedia.com/doc/1G1-54181967.html

Since they claim to have phosphoric acid for computer chip making, my guess is that they should be able to remove trace amounts of impurities from phosphoric acid.

I wish you the best,

Eugene

RSX:
I believe the high concentration of Phosphoric acid coupled with the large volume would make an IX plant huge and expensive. Consider Liquid-liquid Reactive Solvent Extraction. Contact Cognis ion transfer Technology

G

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