plante1999
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Theoretical photocatalyzed oxidation of halides
I got an idea of a silver catalyzed oxidation of halide using various oxidizer. It is known that silver halides (excluding fluoride) decompose to
there composing element in light. It is also known that silver surface is oxidized easily. I thought that if a bromide solution, a suitable oxidizer a
small amount of sulphuric acid was in solution, and a silver piece was added in presence of light, it could be possible that silver oxidize in
surface, the acid increase the solubility and the bromide do metathesis with the silver sulphate. Then light would turn the bromide to bromine and
silver metal.
2Ag + 'O' -) Ag2O
Ag2O + H2SO4 -) H2O + Ag2SO4
Ag2SO4+ 2NaBr -) 2AgBr + Na2SO4
2AgBr -) 2Ag + Br2
Br2 + H2O -) HOBr + HBr
HOBr + HBr + Na2SO4 -) NaBr + NaOBr + H2SO4
3NaOBr -) NaBrO3 + 2NaBr
Overall:
NaBr + 3'O' -) NaBrO3
One could then filter to get most of his silver back, since silver halide are mostly insoluble. Take note that it would be better to use the
corresponding 'Hydrohalic' acid.
I never asked for this.
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Adas
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I don't think that this reaction can proceed.
Rest In Pieces!
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AndersHoveland
Hazard to Other Members, due to repeated speculation and posting of untested highly dangerous procedures!
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Chlorine oxidizes bromide to bromate in the presence of sunlight. This is actually a significant problem with some water reservoirs. Los Angeles
Ivanhoe Reservoir is using a creative strategy to try to solve this problem, covering their reservoir with floating black plastic balls to try to
block sunlight, and thus prevent carcinogenic bromates from forming.
I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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plante1999
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It is equilibrum, and there is no need for sulphuric acid, the need is for an acid.
I never asked for this.
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Hexavalent
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What favours this as opposed to chlorine oxidizing bromide to bromine? Theoretically, as chlorine is a more powerful oxidizing agent, it would capture
an electron from the bromide anion, oxidzing it to a neutral bromine atom and producing a chloride anion.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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elementcollector1
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Quote: Originally posted by Hexavalent  |
What favours this as opposed to chlorine oxidizing bromide to bromine? Theoretically, as chlorine is a more powerful oxidizing agent, it would capture
an electron from the bromide anion, oxidzing it to a neutral bromine atom and producing a chloride anion. |
Entirely true. I don't think chlorine and bromide can make bromate.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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Hexavalent
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Actually, thinking about it, it may be possible....would the photolytically-induced oxidation be caused by a radical mechanism? If so, just how does
sunlight act as a "catalyst"?
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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AJKOER
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| Quote: Originally posted by AndersHoveland | | Chlorine oxidizes bromide to bromate in the presence of sunlight. This is actually a significant problem with some water reservoirs. Los Angeles
Ivanhoe Reservoir is using a creative strategy to try to solve this problem, covering their reservoir with floating black plastic balls to try to
block sunlight, and thus prevent carcinogenic bromates from forming. |
Some discussion of reaction paths may aid some clarity. First,
2 NaBr + Cl2 --> 2 NaCl + Br2
Cl2 + H2O <--> HOCl + HCl
Now, per Watts' Dictionary of Chemistry, HOCl can oxidize I2 (also S and P and I would believe Br2) all the way to Iodate. For Bromine, I would
similarly expect:
Br2 + H2O <--> HBr + HOBr
HOCl + HBr <--> BrCl + H2O ( see http://homepage.uibk.ac.at/~c724117/publications/voegele02-j... equation 2)
HOCl + BrCl --> Cl2 + HOBr (see http://infoscience.epfl.ch/record/33222/files/EPFL_TH2746.pd... equation (4.6.12) )
3 HOBr --uv-> 2 HBr + HBrO3
and the bromate is formed. The references provided will also provide some insights on process.
Note also:
HBr + BrCl --> HCl + Br2 ( see http://www.deepdyve.com/lp/american-institute-of-physics/a-q... equation R2 )
As previously noted: HOCl + HBr <--> BrCl + H2O, so
HOCl + 2 HBr --> HCl + Br2 + H2O
[Edited on 5-1-2013 by AJKOER]
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