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Author: Subject: Bleach degradation by UV light (electrolysis)
Antiswat
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[*] posted on 10-9-2021 at 06:16
Bleach degradation by UV light (electrolysis)


most know that bleach degrades with UV, i looked it up if UV had ever been combined with electrolysis and found nothing on it.
the synthesis of chlorates relies on bleach to break down into chlorate and chloride from hypochlorite
how efficient is UV really at causing this breakdown? could this massively boost efficiency? any input is appreciated

UV might also apply to iodate/bromate production




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macckone
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[*] posted on 10-9-2021 at 07:53


Chlorate is degraded by UV light into oxygen and chloride.
This is used in chlorate removal from water.

Heat causes disproportionation.
In any case degrading bleach is a horrible way to make chlorate.
If you are asking if the 'bulk reaction' could be accelerated the answer is yes.
If you are doing electrolysis the obvious answer is just not to cool the electrolyte as much.
Getting a decent rate usually heats up the solution quite sufficiently.
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[*] posted on 11-9-2021 at 04:03


but do we have any guesses to chlorate vs hypochlorite degradation rates in UV light? it has to be benefitial to make sense

im finding something on chlorate reduction into chloride using UV L, UV M and UV B but also using reducing agents, bulk producing chlorate is interesting as you can use it to form oxygen gas in situ so high efficiency is something you want, and i believe with my 40A 5V setup in 1L glass jar im doing maybe 10% efficiency with platinum and titanium electrodes- very poor.




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mysteriusbhoice
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[*] posted on 13-9-2021 at 20:43


Quote: Originally posted by Antiswat  
but do we have any guesses to chlorate vs hypochlorite degradation rates in UV light? it has to be benefitial to make sense

im finding something on chlorate reduction into chloride using UV L, UV M and UV B but also using reducing agents, bulk producing chlorate is interesting as you can use it to form oxygen gas in situ so high efficiency is something you want, and i believe with my 40A 5V setup in 1L glass jar im doing maybe 10% efficiency with platinum and titanium electrodes- very poor.


40 amps in 1 liter how is your electrolyte not boiling!!
without a large cooling bath it will get up to 95 Celsius at that current.

I ran a perchlorate cell at 36 amps one time 1 liter and even with a cooling it had a temp of 80 to 85 Celsius.
The only way to even get 40 amps is to have an electrode distance of 0.9cm from anode to cathode and having 2 cathodes on both sides of the anodes.

also if you are running at 40 amps then I assume you have a large cooling jacket to prevent your cell from reaching boiling point like it did for me once. Just use pH control with 8 grams of MgCl2 as buffer and 15% HCl addition every 2 days while keeping temp above 60 Celsius. the HCl added every 2 days will not release chlorine when added due to presence of Mg(OH)2 which immidiately reacts to regenerate the MgCl2.

[Edited on 14-9-2021 by mysteriusbhoice]
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[*] posted on 14-9-2021 at 09:12


but the chlorate production reaction doesnt consume chlorine gas, it forms Cl and OH in equillibrium, it has pH 7 already, i cant find any references on magnesium chloride addition to chlorate cell, adding MgCl2 could form insoluble Mg(OH)2 deposit on the cathode ruining the whole process, do you have a reference on magnesium chloride as a buffer?
you should end up with the magnesium hydroxide precipitating out on the cathode, turning the electrolyte more acidic of what i can see.

i might wanna test the actual amperage output, the cell is running quite warm




~25 drops = 1mL @dH2O viscocity - STP
Truth is ever growing - but without context theres barely any such.

https://en.wikipedia.org/wiki/Solubility_table
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macckone
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[*] posted on 15-9-2021 at 21:58


Antiswat,
Your supply may be capable of 40 amps but are you using 40 amps?
Yes you will get hydroxide precipitate but it won't stop the reaction.
It will fall to the bottom. You add HCl to convert it back to the chloride.
At neutral pH some chlorine is generated.
At basic pH it forms hypochlorite in situ.
But at neutral pH the overall process is more efficient.
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mysteriusbhoice
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[*] posted on 15-9-2021 at 23:02


Quote: Originally posted by Antiswat  
but the chlorate production reaction doesnt consume chlorine gas, it forms Cl and OH in equillibrium, it has pH 7 already, i cant find any references on magnesium chloride addition to chlorate cell, adding MgCl2 could form insoluble Mg(OH)2 deposit on the cathode ruining the whole process, do you have a reference on magnesium chloride as a buffer?
you should end up with the magnesium hydroxide precipitating out on the cathode, turning the electrolyte more acidic of what i can see.

i might wanna test the actual amperage output, the cell is running quite warm


The magnesium deposit on the cathode can affect the resistance yes but the resulting precipitate is ionically conductive and infact prevents reduction of chlorate at the cathode.
This however does have an increase in operating voltage and if the layer is too thick then yes it will ruin the process.
High temps above 60 and high current density above 80ma/cm^2 can crack the layers as they form thus not increasing the operating potential by much.
I always operate my cells in these conditions thus I had no problems with calcium and magnesium and infact they help a lot.
Industrially though they have low operating voltages of 3 volts and have electrode spacing so close that calcium and magnesium oxides will damage the anodes if the cathode growths touch them.
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[*] posted on 17-9-2021 at 10:26


interesting thing: in industrial settings they tend to use steel cathodes even with platinum. how cheap is that, the main drawback is that there is <significant corrosion> once the electrolysis is stopped, but once its running the steel electrodes are perfectly safe
as for surface area, im sure im absolutely abusing my electrodes- but then again i dont have an exact number on how much im putting through them so if using correct operational conditions is a must then i cant use it, hard to find widenecked glass containers, and i also have to consider cell temperature so i cant just scale it up infinitely either. i do use chromate additive and it seems to do a major difference




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https://en.wikipedia.org/wiki/Solubility_table
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mysteriusbhoice
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[*] posted on 18-9-2021 at 05:28


Quote: Originally posted by Antiswat  
interesting thing: in industrial settings they tend to use steel cathodes even with platinum. how cheap is that, the main drawback is that there is <significant corrosion> once the electrolysis is stopped, but once its running the steel electrodes are perfectly safe
as for surface area, im sure im absolutely abusing my electrodes- but then again i dont have an exact number on how much im putting through them so if using correct operational conditions is a must then i cant use it, hard to find widenecked glass containers, and i also have to consider cell temperature so i cant just scale it up infinitely either. i do use chromate additive and it seems to do a major difference


exact numbers help a lot in this case you know. basically unless you know how much amps are coming through then you wont be able to calculate runtimes or know how far you are pushing your electrodes.

for example a 5*15 cm MMO anode can run up to 30 amps at a given current density of 200ma/cm^2 and last for 20 years given 24/7 operation of such an electrode at the proper conditions.

30 amps at 5 volts is like 150 watts of power and some of that goes into heat which usually heats up a cell really hot and such cells emit lots of chlorine when pH controlled which is enough to choke you out without a proper vent setup if not ran outside.
The electrode strips also have to be tightly clamped or pre copper plated or they can glow incandescent which happened to me once.

As for stopping the electrolysis while the electrodes are in is stupid whichever anode you use.
Never stop a cell with electrodes still inside it and always keep the power on even as you are removing them.

[Edited on 18-9-2021 by mysteriusbhoice]
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[*] posted on 19-9-2021 at 02:11


i believe the mmo/titanium corroding in a cell that doesnt run isnt entirely true, maybe significantly worse corrosion compared to in electrolyzing solution, but i have had them in solution for days with no power on and saw no visible difference on the electrodes
in this case i think bleach is a bit overrated

i did come across a video where a guy is using persulfate, he advises 4g/L which you replace the evaporated water with, so its an electrolyte that gets spent
i cant remember entirely about persulfate but i believe its only doable to make using ammonium sulfate, and you dont wanna add that to chlorate cell thats running
not sure what type of persulfate he added in the video

pH does play a role and he presented several graphs indicating 40-70% efficiency gap based on incorrect pH, so its not like a 300% difference really




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https://en.wikipedia.org/wiki/Solubility_table
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macckone
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[*] posted on 24-9-2021 at 07:40


You can add sulfate and it will get converted to persulfate.
Best to use the same ion as your chloride.
Either sodium or potassium depending on what your ion is.
It doesn't get spent per se, He is probably using sulfuric acid to keep the pH correct and it gets converted to persulfate.
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