[az8104 (OP)]

Hi all.  I am in need of help to figure out the stability of Silver Bromide.  I am carrying out a precipitation reaction using liquid bromine to remove as much soluble silver from water as possible.  What I can't figure out is how stable this compound is in regular light and sun light.  From what I have read, silver halide compounds (like silver bromide) breakdown in sunlight to potentially produce bromine gas but I don't know to what extent.  Bromine gas is a health hazard and therefore I would like to avoid it if thats whats produced.

Any help is much appreciated.

[paul cotter]

But you are planning to use elemental bromine initially so I don't think the small amount released by photolysis would  present a problem. Bromine is however a particularly nasty substance and I would recommend looking for an alternative process. Silver pseudohalides  also undergo photolysis, eg silver azide turns black on light exposure.

[Bored chemist]

I am carrying out a precipitation reaction using liquid bromine to remove as much soluble silver from water as possible.

What are the circumstances where "my water has too much silver in it" is a problem?
If the solution is present as silver ions ten it makes more sense to precipitate it using potassium bromide, (which is easy to handle) rather than bromine (which is not, and which will not work as well).

[az8104 (OP)]

Here is a bit more information.  The concentration of soluble silver is upwards of 20,000 ppm in soluble free or bound form (tied to EDTA or EDA).  I am using a 40% sodium bromide solution for precipitation.  I am able to precipitate silver to ppb levels with this reaction.  I am trying to figure out how much bromine gas would be generated if the precipitate goes through photolysis due to sunlight. 

The concern is related to safety and bromine gas generation.  I am trying to figure out a way to calculate this but have very limited information on how to do so.  Or any other chemical recommendations to react out soluble silver to ppb levels and avoid bromine gas emission altogether.

[William Hardy]

Yes, silver bromide is affected by light. It is generally used to precipitate into silver like here the authors have used AgBr for Ag Nps preparation by UV light(https://pubs.rsc.org/en/content/articlelanding/2016/tc/c5tc02616d) anyway it is still unstable with visible light. You can try using a aluminum foil to cover the beaker and then proceed. I've personally used aluminum foils while dealing with silver salts!

[Bored chemist]

I am trying to figure out how much bromine gas would be generated if the precipitate goes through photolysis due to sunlight. 

Enough to make a dark smudge of silver on the surface of the AgBr.
Hardly enough to detect- certainly not enough to worry about.

[amadjan]

The solubilities of AgBr(s) in NaBr solutions and AgI(s) in NaI solutions were measured at elevated temperature. Referring to the following general reactions (where X = Cl, Br, or I): AgX(s) ⇋ Ag+ + X− (1) AgX(s) ⇋ AgX(aq) (2) AgX(s) + X− ⇋ AgX2− (3) AgX(s) + 2X− ⇋ AgX32− (4) the following equilibrium constants were obtained: log K2,Br = −4.01 ± 0.20 (200°C) and −3.12 ± 0.20 (300°C); log K3,Br = −1.81 ± 0.10 (200°C) and −1.01 ± 0.10 (300°C); log K3,I = −2.46 ± 0.20 (150°C), −1.92 ± 0.20 (200°C) and −1.47 ± 0.10 (250°C); and log K4,I = −1.9 ± 0.4 (150°C) and −2.2 ± 0.4 (200°C)
dont know if this helps copied it from my friends account.