I'm considering using sodium polyacrylate grains to absorb spills of a relatively strong Ammonium Hydroxide solution. Will the SAP (super absorbent polymer) only absorb the water, and in effect make the remaining solution a higher concentration of NH4OH? Or would some of the dissolved gas also be held by the SAP? I am a mechanical engineer by trade, so I can research any terms you use, but my chemistry background is limited.
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$\begingroup$ Since NH3 is held very tightly by H2O (700 volumes of gaseous ammonia can dissolve in one volume of liquid water), at a guess, most of the NH3 would stay with the water. That said, does NH3 chemically adversely affect SAP? If you can't find that in the literature, perhaps a small-volume experiment would help. You might also include a mild acid, such as citric acid, mixed with SAP, to make a non-volatile salt. $\endgroup$– DrMoishe PippikCommented Jul 14, 2021 at 0:05
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The available literature is conflicting. On the one hand, a website claims that its SAP is unsatisfactory for absorbing ammonia, acetone and isopropanol (Ref 1).
On the other hand, there is a patent that claims an SAP polymer specifically for absorbing ammonia (Ref 2).
The monomers that are used to make the super absorbent polymer may be sodium or ammonium acrylate, or acrylic acid itself. It has been reported that multivalent cations inhibit the swelling of the SAP by tying separate chains together, and it could be that even monovalent cations in large quantities could inhibit swelling.
It does seem that an SAP polymerized from an acid monomer could react with NH3 or NH4OH to give the ammonium salt, which should swell the SAP just as if it were polymerized from the ammonium salt itself.
Since there are so many grades of SAPs, several are surely acid-containing, and would be useful for containing ammonia spills. Other grades, based on polymers of salts of acidic monomers would be unsuitable.
The preferred course of action, then, would be to contact manufacturers or distributors of SAPs and state your requirements.
Ref 1. https://recycphp.com/en/absorption-domestic-liquids-sodium-polyacrylate/
answered Jul 14, 2021 at 2:53