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I'm using Ammonium Cerium Nitrate to neutralize phosphate-buffered saline solutions containing 0.1% Sodium Azide. I add 0.55 grams of Ammonium Cerium Nitrate into 100 mL of this 1XPBS + 0.1% NaN3 solution and am able to neutralize the NaN3.

Will the resulting solution have any negative, harmful, effects if flushed down the drain? My main concern is polluting ground water or corroding our sewerage system.

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    $\begingroup$ Googling around, most sources I can find recommend neutralization of azide with nitrite salts, followed by acidification. Is there a reason you have to use cerium to neutralize instead of the common, recommended method? $\endgroup$ – Curt F. Dec 5 '16 at 17:03
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    $\begingroup$ See e.g. unige.ch/sciences/chiorg/matile/… $\endgroup$ – Curt F. Dec 5 '16 at 17:03
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    $\begingroup$ See also unomaha.edu/business-and-finance/support-services/_documents/… $\endgroup$ – Curt F. Dec 5 '16 at 17:05
  • $\begingroup$ I was trying to find a more simple method of neutralizing NaN3 rather than having to use Sodium Nitrite and Sulfuric Acid. If I had a low concentration of NaN3 (less than 0.1%) in Phosphate Buffer Saline can I simply heat the solution as a form of neutralization? $\endgroup$ – Molly Dec 5 '16 at 20:20
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    $\begingroup$ I don't know about temperature, but simple bleach also seems to do the job, and has the advantage of being both simpler than $\ce{(NH4)2Ce(NO3)6}$ and simpler than the nitrite/acid method mentioned earlier. ncbi.nlm.nih.gov/pubmed/20667654 $\endgroup$ – Curt F. Dec 5 '16 at 20:29
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I think that you are doing fine!

The azide anion can be used for quite some amazing chemistry, but it's rather toxic and harmful for the environment.

Admittedly, I'm too lazy right now to look up the redox potentials or to write the reaction equation, but

CAN should be able to oxidize $\ce{N3-}$ all the way up to $\ce{NO3-}$, which is safe to be disposed.


Update

Judging from memory can result in bad advices!

A closer look at the SDS of both compounds shows that both have

  • H410 Very toxic to aquatic life with long lasting effects. and

  • P273 Avoid release to the environment.

Consequently, the combined solutions (with excess of CAN) should not be poured down the drain, but collected (aqueous inorganic waste).

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  • $\begingroup$ Should there be cause for concern about the excess CAN that is disposed along with the neutralized Sodium Azide? The SDS of the CAN stated that it was toxic to aquatic life. $\endgroup$ – Molly Dec 5 '16 at 15:26
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    $\begingroup$ @Molly Excellent point! Admittedly, I judged from memory and I was wrong about effects of CAN, Apologies! I will update my answer. $\endgroup$ – Klaus-Dieter Warzecha Dec 5 '16 at 16:23
  • $\begingroup$ Could I simply heat my 0.1% NaN3 solution as a way of neutralization? $\endgroup$ – Molly Dec 5 '16 at 20:21

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