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What is the best method to extract ammoniumsulfate from water?

The assignment is as follows:

Manure is being processed and the product left is a mixture between water and ammonium sulfate, transporting the mixture costs a lot of money. So we only want the ammonium sulfate.

What is the best method to do this on a big scale? Evaporation isn't a good option since it costs too much energy to heat the big amounts of water.

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  • $\begingroup$ Depends on if you want the sulfate or ammonium or both. $\endgroup$ – Zhe Jan 30 '17 at 23:25
  • $\begingroup$ You would probably have to add a lot of grain alcohol to precipitate the ammonium sulfate out (ammonium sulfate is insoluble in ethanol), and recovering the alcohol for re-use wouldn't be free either. Does this route look too costly? $\endgroup$ – airhuff Jan 31 '17 at 1:44
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Evaporation isn't a good option since it costs too much energy to heat the big amounts of water.

Is it? I've seen prices around USD 130-150 per ton (minimum order of 25 tons) for ammonium sulfate with a purity around 99%. You might want to calculate the costs to operate a production plant using natural gas (or other fuels) for evaporation yourself.

There is however a different energy source that you might want to take into consideration: the sun.

Evaporation of water from solutions of sodium chloride in open ponds by solar heating alone has a long tradition in the production of sodium chloride in the form of sea salt.


Update

Ammonium sulfate will not evaporate from the open ponds. At temperatures between 235-280 °C, it will start to decompose.

However, if surface temperatures reach that level under irradiation with unconcentrated sunlight, the fate of the ammonium sulfate is the least of your worries ;)

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  • $\begingroup$ Thanks for your quick answer, I have a question, as soon as the evaporation in an open pond starts, won't the ammonium sulfate start to evaporate too? $\endgroup$ – Karim Leurink Jan 31 '17 at 8:47
  • $\begingroup$ @KarimLeurink I've updated my answer. $\endgroup$ – Klaus-Dieter Warzecha Jan 31 '17 at 9:11

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