Dechlorinators do NOT need oxygen to work

AvalancheDave

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This is a new myth I see popping up on the Internet. Dechlorinating agents can react with oxygen but don't have to in order to reduce chlorine to chloride. All the reactions are Google-able and clearly don't involve oxygen yet some people think dechlorinators won't even work in the absence of oxygen.
 

Cody

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The irony I see in this is that if your water in theory was “lacking” enough oxygen for the dechlorinating agent to work wouldn’t you have more issues to worry about than dechlorinating the water....
 
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AvalancheDave

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SS = sodium sulfite
SBS = sodium bisulfite
AA = ascorbic acid
HP = hydrogen peroxide
CTS = calcium thiosulfate

Comparison of Reaction Rates and Relative Efficiencies for Various Dechlorination Chemicals by Benoit M. Hermant1 and Onita D. Basu, Ph.D., P.Eng

dechlorination reactions 1.png

dechlorination reactions 2.png


Kinetics of Tap Water Dechlorination and Aquatic Health Impacts of Selected Dechlorination Chemicals by Bhagya N. Weerasinghe

dechlorination reactions 3.png
 
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AvalancheDave

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Cody said:
The irony I see in this is that if your water in theory was “lacking” enough oxygen for the dechlorinating agent to work wouldn’t you have more issues to worry about than dechlorinating the water....
Check out this reaction between sodium thiosulfate and oxygen:



"This reaction takes place at a temperature of 60-120°C."
 

Cody

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So I have not seen anything like this personally. But I see enough stuff floating around the internet that I can imagine people taking and running with this.

But is the thought that people believe their "insert dechlorinator brand" is not going to work unless the properly oxygenate their water during a water change? And that is what is going around?
 
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AvalancheDave

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Cody said:
So I have not seen anything like this personally. But I see enough stuff floating around the internet that I can imagine people taking and running with this.

But is the thought that people believe their "insert dechlorinator brand" is not going to work unless the properly oxygenate their water during a water change? And that is what is going around?
It went from dechlorinators can reduce oxygen to dangerous levels to dechlorinators need oxygen to work.

Mostly in part due to an Aquarium Co-op video where he talks about the "facts" and "truth" about dechlorinators without evidence or experimentation. I just listened to it again at 2X speed and didn't catch him saying that dechlorinators need oxygen to work though I thought I vaguely remember him saying it the first time I watched.

I anticipate that's what some people will say when I post my video where a 40X overdose of Prime only caused a minor and momentary depression in dissolved oxygen levels.
 

-Mak-

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AvalancheDave said:
Mostly in part due to an Aquarium Co-op video where he talks about the "facts" and "truth" about dechlorinators without evidence or experimentation. I just listened to it again at 2X speed and didn't catch him saying that dechlorinators need oxygen to work though I thought I vaguely remember him saying it the first time I watched.
That would be around 3:20 in the video

This might be on the limits of my chem knowledge, but what do you make of sodium thiosulfate being called an oxygen scavenger and reducing agent?
 
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AvalancheDave

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-Mak- said:
That would be around 3:20 in the video
I don't see him talk about dechlorinators requiring oxygen to function. The idea must have sprung up from somewhere though...

-Mak- said:
This might be on the limits of my chem knowledge, but what do you make of sodium thiosulfate being called an oxygen scavenger and reducing agent?
All the sulfur-based dechlorinators are oxygen scavengers and reducing agents but some are more effective than others. The same article mentions it just a few lines down:

dechlorination reactions 4.png
 

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AvalancheDave said:
I don't see him talk about dechlorinators requiring oxygen to function. The idea must have sprung up from somewhere though...



All the sulfur-based dechlorinators are oxygen scavengers and reducing agents but some are more effective than others. The same article mentions it just a few lines down:

dechlorination reactions 4.png
Right, which is perhaps where the whole idea comes from
 

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