Reef Chemistry Question of the Day #169 Reactions of Ozone

[Randy Holmes-Farley]

Reef Chemistry Question of the Day [HASHTAG]#169[/HASHTAG]

Ozone (O3) is sometime used to reduce the yellowing of reef aquarium water by reacting with dissolved organics, and it works very well for that purpose.

Ozone also reacts with a number of other chemicals in seawater to produce a variety of compounds, some of which are toxic.

Which of the following is least likely to be one of these other reactions?

A. Reaction with ammonia (NH3) to form nitrate (NO3-)
B. Reaction with nitrate (NO3-) to form nitrite (NO2-)
C. Reaction with bromide (Br-) to form hypobromite (BrO-)
D. Reaction with bromide (Br-) to form bromate (BrO3-)

Note the transformations described might take more than one reaction step.

Good luck!





































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[beaslbob]

I give up.

Which one is it?

 

[Cory]

I think its b thats least likely to be produced

 

[beaslbob]

Note the transformations described might take more than one reactions step.

Good luck!

So is the a twelve step program?

 

[Taservices]

I'm thinking B as well, but I'm not positive.

 

[ianf77]

D

Oops... LEAST... Likely

 

[Lynn52]

B

 

[Mark Lawson]

C

 

[FL_Reefer]

D, is my final answer.

 

[SaltyJD]

A

 

[Myka]

I'm going with B because O3 would oxidize NO2 to NO3, not the other way around. So maybe my answer is B. I don't know what to make of C and D though.

 

[Randy Holmes-Farley]

And the answer is...B. Reaction with nitrate (NO3-) to form nitrite (NO2-)

Ozone is a strong oxidizer, but nitrate (NO3-) is more oxidized than is nitrite (NO2-), so ozone cannot drive that reduction reaction.

Ozone does do all of the others, as i describe in this article:

Ozone and the Reef Aquarium, Part 1: Chemistry and Biochemistry by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2006-03/rhf/index.php

and some pertinent sections from it:


Ammonia

Another of ozone's potential reactions and its byproducts with inorganic compounds in seawater is with ammonia. In fact, ozone is quite effective at converting ammonia into nitrate. The reaction is fast enough that if sufficient ammonia is present in seawater, it will happen preferentially to reactions that lead to bromate.3,12,13 An intermediate species in the process is bromamine (the bromine equivalent ofchloramine), but fortunately (because it is toxic) it usually is further oxidized to bromide and nitrate.

BrOH + NH3 --> NH2Br

NH2Br + O3 + 2OH- --> NO3- + Br- + 2H2O

Presumably it is not harmful, and may be beneficial to reduce the ammonia to nitrate more rapidly. It may lead to higher nitrate concentrations in the aquarium, however, and may also lead to a different ratio of nitrogen export via different mechanisms because some methods (such as growing some species of macroalgae) prefer ammonia over nitrate.


Halogens

When ozone is applied in seawater in concentrations higher than are naturally present, a larger variety of chemical reactions take place. Chief among these is oxidation of bromide to hypobromite:

O3 + Br- --> BrO- + O2

BrO- + H2O --> BrOH + OH-

The first reaction is very fast, and the half life of unreacted ozone in water with a lot of bromide (such as seawater) is on the order of a few seconds.8 Because hypobromous acid's pKa (in freshwater) is about , it is primarily in the protonated (uncharged form) in seawater, but a significant amount of BrO- is also present. The hypobromous acid is itself a strong oxidizer and can rapidly oxidize other organic or inorganic materials.

The hypobromous acid can also react in a variety of ways (including disproportionation and additional oxidation with ozone) to form bromate:

BrOH --> --> --> BrO3-

The hypobromous acid can also be catalytically broken down by ozone to return to bromide:

BrOH+ O3 --> 2O2 + Br- + H+

About extensive ozonation of seawater, one group concluded:

"Ozonization of seawater oxidizes bromide ion to Br (hypobromous acid and hypobromite ion) and then to bromate. If seawater is ozonized for >60 min, essentially all bromide is converted to bromate."

That level of ozonation, however, is far more than would take place in a reef aquarium. The various reactions leading to bromine-containing byproducts of water's ozonation have been extensively studied (especially in the context of disinfecting fresh drinking water that contains bromide). Nevertheless, it is a complex problem. One recent review stated:

"Because bromate formation during ozonation of bromide-containing waters is a highly non-linear process, kinetic modeling has been applied to improve mechanistic understanding and to predict bromate formation. The full model consists of more than 50 coupled kinetic equations which can be solved simultaneously with a computer code…"

and then went on to say,

"the predictive capabilities of such models for the ozonation of any water should not be overestimated."

Well, we won't try to calculate what happens in reef aquaria, but we will conclude that bromate and hypobromite may be significant.

Bromate is typically the longest lived after ozonation of bromide-containing water. It is, in fact, one of the biggest concerns with ozonation as a purification method for drinking water, because bromate is a suspected carcinogen. For this reason, the US EPA limits it to only 10 ppb in drinking water. So in considering the properties of the treated seawater in aquaria, both BrOH/BrO- and BrO3- must be considered.

There is at least one study in the literature of bromate in a seawater aquarium.10 Here the ozone was used for disinfection, so the doses used may be higher than many aquarists employ. I also do not know whether or how effectively they treated the post ozone water with activated carbon. Nevertheless, the bromate levels in the Living Seas exhibit at Walt Disney World's Epcot Center were tracked. The researchers studying this display found that bromate had risen to about 0.6 ppm (with nitrate at about 600 ppm). After adding a batch denitrifying system, the bromate and nitrate concentrations began to drop, suggesting a sink for bromate that might well exist in many reef aquaria as well (that is, in systems or locations where denitrification takes place).

 

[Myka]

 

[The 262 Reef]

The answer is B. My question though is how do i get rid of bromate? BRo3- is really bad for sps and lps fleshy tissue. It makes it recede very quickly and infact will kill the coral very rapidly, i know this in my own personal experience with a poseidon ozone generator being left on at level 8 for 10 hrs in a max capacity i have at 185 gallons of water. Ive been suffering from this accidental mistake leaving it on and fell asleep. Lesson learned, apex on schedule now with dedicated programmed outlet. I lost a huge soccer ball sized purple stylophora colony and baseball sized acros including pc rainbow confetti cake. Spent alot of money and lost it all. Unfortunately i dont like sps as these seem to be so picky. All other corals except for duncan corals seem to be fine from this large exposure. I do know however that activated carbon seems to convert this BRo3 back to a non toxic form in lack of better words. I know this by reading alot of your articles that are quite lengthy. And i spent 6 hrs going down your rabbit hole of very interesting information im paranoid to run ozone and have been battling this slow die off for over a month now. However, sea fans hammers frogspawns torches and soft corals seem to be completely unaffected. I have noticed also that gsp is a huge signal as to when the ozone is on because it pulls back into its chutes very quickly and look like singed hairs.. not full length and very curly looking... every time. Im so curious as to learn more and how i can begin to reverse my mistake. I have exchanged carbon multiple times now and use about 3 cups of it. I want a low nutrient system so i run gfo and carbon as well as uv and ozone. Im going to stop ab+ liquid addative and use only fresh frozen foods as i just seem to constantly struggle to keep my phosphate below .08 and want it around .01 .02 .03. Any information would be incredibly awesome. I feel im missing alot

 

[Randy Holmes-Farley]

The answer is B. My question though is how do i get rid of bromate? BRo3- is really bad for sps and lps fleshy tissue. It makes it recede very quickly and infact will kill the coral very rapidly, i know this in my own personal experience with a poseidon ozone generator being left on at level 8 for 10 hrs in a max capacity i have at 185 gallons of water. Ive been suffering from this accidental mistake leaving it on and fell asleep. Lesson learned, apex on schedule now with dedicated programmed outlet. I lost a huge soccer ball sized purple stylophora colony and baseball sized acros including pc rainbow confetti cake. Spent alot of money and lost it all. Unfortunately i dont like sps as these seem to be so picky. All other corals except for duncan corals seem to be fine from this large exposure. I do know however that activated carbon seems to convert this BRo3 back to a non toxic form in lack of better words. I know this by reading alot of your articles that are quite lengthy. And i spent 6 hrs going down your rabbit hole of very interesting information im paranoid to run ozone and have been battling this slow die off for over a month now. However, sea fans hammers frogspawns torches and soft corals seem to be completely unaffected. I have noticed also that gsp is a huge signal as to when the ozone is on because it pulls back into its chutes very quickly and look like singed hairs.. not full length and very curly looking... every time. Im so curious as to learn more and how i can begin to reverse my mistake. I have exchanged carbon multiple times now and use about 3 cups of it. I want a low nutrient system so i run gfo and carbon as well as uv and ozone. Im going to stop ab+ liquid addative and use only fresh frozen foods as i just seem to constantly struggle to keep my phosphate below .08 and want it around .01 .02 .03. Any information would be incredibly awesome. I feel im missing alot

Sorry to hear about the loses.

Using GAC on the ozone effluent should get rid of problematic levels of bromate and other highly oxidizing compounds.

 

[The 262 Reef]

Sorry to hear about the loses.

Using GAC on the ozone effluent should get rid of problematic levels of bromate and other highly oxidizing compounds.

i was very sad when i lost all these corals growing them out from little twigs.. even my GF was very sad. but i mourned for a month and its time to move one and learn.


I personally want to thank you for all of your knowledge and expertise. i look forward to reading more of your articles and information as I too desire to learn alot about chemistry, ive always found it so fascinating. i replaced the activated carbon immediately upon reading about how GAC will remove the oxidants. it was a saving moment for my tank and as i look at the corals today as i just got home from work, everything appears to be on the beginning of the up rise and i know now how to help prevent this from continuing and happening again. i Currently use a eshopps HOB 75g skimmer as a dedicated reaction chamber for ozone for 1 hr at level 5 from midnight to 1am. according to the brs website it states to start with 15mg/hr per 25 gallons of tank volume. i have carefully tracked volume since the beginning of my tank 2 - 3 years ago and im very confident with 185 gallons total tank volume. the poseidon states its a true 220mg/hr ozone generator. so based on my knowledge this means, [22mg/hr * (set level)]. 110mg/hr. 185g/25 = 7.4. so i believe level 5 would be a good starting point especially when im not always aware of if the desiccant is fully incapacitated. which could lead to a 50% loss in efficiency. this gives me a cushion and a peace of mind if something were to happen and be bad, it wont be as bad as it could be, i suppose thats an excuse to not do better but im reaching out on the subject to better inform myself.

I do have one question, in the same chamber as my main skimmer is the HOB ozone skimmer.. but my gfo and activated carbon reactor combo are in the last chamber in with the return pumps. is this effective? is there a more effective way? i thought of hanging a mesh sock with GAC on the outlet of the eshopps skimmer for now and using CAD to draw up a dedicated unit per say.. to attatch to the outlet. I am in the midst of starting my 3D printing business and have alot of products already produced and tested alot. however i am still working on building the website. what would you recommend besides purchasing the $700 unit. i forget the name of it now. ment for ozone reation with a built in carbon chamber on the outlet.

thank you again =]