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Topic: How to purify Na2SO4 ?  (Read 664 times)

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Offline metallurgy

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How to purify Na2SO4 ?
« on: February 11, 2020, 05:55:00 AM »
If Sodium sulphate waste product contains these materials:

Code: [Select]
84 ~ % Na2SO4
--% Na2CO3
--% NaCl
--% NaF
pH=8.00 (in 5% solution)

How to purify it to obtain pure Na2SO4 (99%)?

Offline billnotgatez

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Re: How to purify Na2SO4 ?
« Reply #1 on: February 11, 2020, 11:48:46 AM »
You have to show your attempts or thoughts at solving the question to receive help.
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http://www.chemicalforums.com/index.php?topic=65859.0

Offline metallurgy

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Re: How to purify Na2SO4 ?
« Reply #2 on: February 12, 2020, 01:49:41 AM »
You have to show your attempts or thoughts at solving the question to receive help.
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Okay.
There are ways to purify Na2So4 like adding ferric sulphate into solution or fractional cristallization (very old default method), evaporation etc. etc.
https://patentimages.storage.googleapis.com/3a/cf/c9/8b7700c0c8da9a/US1673471.pdf
Removing impurities is important, but i dont know how to purify the industrial waste of sodium sulphate which has NaCL and NaF as these are high rate impurities...

Offline AWK

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Re: How to purify Na2SO4 ?
« Reply #3 on: February 12, 2020, 06:24:00 AM »
Your problem looks technological, I mean a large scale process. Besides, I can guess that you have solid impure sodium sulfate. In this case, the patent you cite may be useful if you adapt it to the composition of the impurities (the patent was intended for purifying the thenardite mineral without dissolving it). Therefore, you need to know the composition of the impurities quite accurately. According to this patent, anhydrous sodium sulfate is obtained. Decahydrate can be obtained by recrystallization. Carbonates and fluorides are relatively easy to remove, but you need to think about what to do with waste sodium chloride containing about half the sodium sulfate by mass.
AWK

Offline metallurgy

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Re: How to purify Na2SO4 ?
« Reply #4 on: February 13, 2020, 03:13:53 AM »
Your problem looks technological, I mean a large scale process. Besides, I can guess that you have solid impure sodium sulfate. In this case, the patent you cite may be useful if you adapt it to the composition of the impurities (the patent was intended for purifying the thenardite mineral without dissolving it). Therefore, you need to know the composition of the impurities quite accurately. According to this patent, anhydrous sodium sulfate is obtained. Decahydrate can be obtained by recrystallization. Carbonates and fluorides are relatively easy to remove, but you need to think about what to do with waste sodium chloride containing about half the sodium sulfate by mass.

Na2CO3 is 1-2% , NaCl 7-8%, NaF around 1%, the waste is solid yes, but the mentioned patent is from 1928, i've found another new patent:
https://patentimages.storage.googleapis.com/b7/72/43/3ff64f01856048/US20060163164A1.pdf

This says adding ferric sulphate into a solution to form suspension, plus they are adding peroxide to remove heavy metals which can be useful to clear impurities? I have no idea what kind of plant can do this as an industrial scale. For doing this may be this patent: https://patents.google.com/patent/US4246241A/en give an idea to separate NaCl from sodium sulphate...

Offline AWK

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Re: How to purify Na2SO4 ?
« Reply #5 on: February 13, 2020, 04:23:44 AM »
The method contained in US20060163164 is used to purify a practically saturated sodium sulfate solution from heavy metal impurities. It is not known if this is needed in your case.
The next patent pertains to the treatment of mixtures with high NaCl content and low Na2SO4, so it probably does not concern your problem.
All technology patents propose technology schemes, generally enough for a chemical engineer to imagine the process. Although sometimes patents have to be read between the lines. Patents are written to claim the process and not to be easily reproduced.
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Offline metallurgy

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Re: How to purify Na2SO4 ?
« Reply #6 on: February 13, 2020, 07:15:45 AM »
Patents are written to claim the process and not to be easily reproduced.
Thanks for this sentence/info. I didn't know this until this time.

I think, firstly i need to focus on how to remove the specific impurities, each by each (NaCl, NaF etc.) from Na2SO4 solution. It can be done by laboratory scale but when we think it thousands of tonnes per day in an industrial scale, i can't find any method/process to reproduce and apply for it..

Offline AWK

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Re: How to purify Na2SO4 ?
« Reply #7 on: February 13, 2020, 08:35:10 AM »
As I wrote in the first post, the removal of carbonates and fluorides is simple (removal, not isolation unchanged).
But all this should be checked in the laboratory.
Depending on the intended use of sodium sulfate, it may be necessary to work out the removal of other impurities present in smaller quantities.
Only after developing technology on a laboratory scale in details you can go to scale up.
AWK

Offline metallurgy

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Re: How to purify Na2SO4 ?
« Reply #8 on: February 16, 2020, 08:34:04 AM »
As I wrote in the first post, the removal of carbonates and fluorides is simple (removal, not isolation unchanged).
But all this should be checked in the laboratory.
Depending on the intended use of sodium sulfate, it may be necessary to work out the removal of other impurities present in smaller quantities.
Only after developing technology on a laboratory scale in details you can go to scale up.
Yes it should be checked in the laboratory but what kind of removal methods should work for this (in the lab scale)?

Offline AWK

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Re: How to purify Na2SO4 ?
« Reply #9 on: February 16, 2020, 09:07:09 AM »
Check phase diagram NaF-Na2SO4-NaCl-H2O and on your knowledge from patents and chemistry sketch your attempt.
AWK

Offline metallurgy

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Re: How to purify Na2SO4 ?
« Reply #10 on: February 20, 2020, 05:30:40 AM »
Check phase diagram NaF-Na2SO4-NaCl-H2O and on your knowledge from patents and chemistry sketch your attempt.
Ok. Do you know what kind of equipments (mechanicals, electricals, chemicals etc.)  used in the purification plant of sodium sulphate?

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