mysteriusbhoice
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Ir-Ta vs Ir-Ru MMO
Most often you see Ir-Ta or Ir-Ru type MMO and I do know the difference but I wonder if anyone prefers one over the other.
Ir-Ta
pros:
can run chlorate cell even up to zero chloride but wont make perchlorate.
more resistant to corrosion the NaOCl electrolysis in non pH controlled cells.
Is also made for oxygen evolution.
better anode to plate with PbO2 for robustness and wont fail even if PbO2 comes off during runs.
Usually rated for higher current densities.
Can do all sorts of electrolysis processes such as sulfuric from gypsum, membrane, precious metal plating etc.
cons:
higher Cl evolution potential thus lower efficiency in pH controlled cells 80% vs 87% for Ir-Ru.
usually more expensive.
Ir-Ru
pros:
More efficient for Cl evolution and operates usually at lower voltages when running in a pH controlled chlorate cell.
Lower cost compared to Ir-Ta.
good and must have for other types of salt electrolysis such as chloro alkali.
more commonly available from various sellers.
cons:
working life is slightly shortened when operating in oxygen evolution conditions (no pH control, low chloride)
only for NaCl or chloride salt electrolysis and cannot do sulfate electrolyte.
releases toxic RuO4 when ran improperly (O2 evolution)
cannot run chlorate cell to zero chloride without damages to the coating due to O2 evolution.
Both these have pros and cons but how many people here use either one and what can they say about these properties while working with them.
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chemistry4frog
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Quote: Originally posted by mysteriusbhoice  | Most often you see Ir-Ta or Ir-Ru type MMO and I do know the difference but I wonder if anyone prefers one over the other.
Ir-Ta
pros:
can run chlorate cell even up to zero chloride but wont make perchlorate.
more resistant to corrosion the NaOCl electrolysis in non pH controlled cells.
Is also made for oxygen evolution.
better anode to plate with PbO2 for robustness and wont fail even if PbO2 comes off during runs.
Usually rated for higher current densities.
Can do all sorts of electrolysis processes such as sulfuric from gypsum, membrane, precious metal plating etc.
cons:
higher Cl evolution potential thus lower efficiency in pH controlled cells 80% vs 87% for Ir-Ru.
usually more expensive.
Ir-Ru
pros:
More efficient for Cl evolution and operates usually at lower voltages when running in a pH controlled chlorate cell.
Lower cost compared to Ir-Ta.
good and must have for other types of salt electrolysis such as chloro alkali.
more commonly available from various sellers.
cons:
working life is slightly shortened when operating in oxygen evolution conditions (no pH control, low chloride)
only for NaCl or chloride salt electrolysis and cannot do sulfate electrolyte.
releases toxic RuO4 when ran improperly (O2 evolution)
cannot run chlorate cell to zero chloride without damages to the coating due to O2 evolution.
Both these have pros and cons but how many people here use either one and what can they say about these properties while working with them.
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i plan on using then IR-Ru electrodes for chloro alkali. i will super-saturate the solution so it wont have zero chloride. regarding pH control can
you elaborate? are you suggesting the naoh compartment cannot have high ph? what range is acceptable.
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mysteriusbhoice
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the anode chamber must not reach pH of 10 or it will cause RuO4 to be formed at the anode as the cell shifts to O2 evolution. This isn't an issue when
NaOH is removed before it reaches 30% concentration in the cathode chamber or better yet continuos flow cells. Because past that there is a drop in
membrane efficiency leading to anode chamber rise in pH.
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chemistry4frog
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| Quote: Originally posted by mysteriusbhoice | | the anode chamber must not reach pH of 10 or it will cause RuO4 to be formed at the anode as the cell shifts to O2 evolution. This isn't an issue when
NaOH is removed before it reaches 30% concentration in the cathode chamber or better yet continuos flow cells. Because past that there is a drop in
membrane efficiency leading to anode chamber rise in pH. |
this seems to be contradictory.
poH + pH = 14
pOh + 10 = 14
pOH = 4,
pOh = -log(x)
4 = -log(x)
x = 0.0001 Molar which is far less than 30%.
It would seem infeasible to maintain 0.0001 Molar in the anode cell of NaOH as it would require one to dilute for ever mole of NaOH generated by the
cell with 10,000 liters of water which would make the cell massive and an expensive water bill.
Am I missing something ?
[Edited on 9-9-2023 by chemistry4frog]
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chemistry4frog
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wait am i mixed up, in a chloro alkali cell, doesnt the anode only get exposed to nacl and the cathode is on the naoh side.
if so then i am fine right??????? the mmo anode will have neutral pH!!
For the cathode in this cell, can i use copper ??
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mysteriusbhoice
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| Quote: Originally posted by chemistry4frog | wait am i mixed up, in a chloro alkali cell, doesnt the anode only get exposed to nacl and the cathode is on the naoh side.
if so then i am fine right??????? the mmo anode will have neutral pH!!
For the cathode in this cell, can i use copper ?? |
In a chloro alkali cell the anode chamber remains at 7 however if concentration of NaOH in the cathode chamber is too high about 30% then flow of
sodium ions stop and increase in pH occurs at the anode chamber.
A copper cathode can be used in either a chlorate or chloro alkali cell ofc copper oxides and gunk will form but not too bad.
It is still wise to have a means to measure the pH because if a leak in the membrane occurs due to bad seal then the anode chamber pH will rise which
is not ideal. If you want to avoid that but at the cost of sacrificing efficiency then the Ir-Ta anode is a lot more robust and can handle it even
when the pH gets too alkaline.
[Edited on 10-9-2023 by mysteriusbhoice]
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chemistry4frog
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| Quote: Originally posted by mysteriusbhoice | | Quote: Originally posted by chemistry4frog | wait am i mixed up, in a chloro alkali cell, doesnt the anode only get exposed to nacl and the cathode is on the naoh side.
if so then i am fine right??????? the mmo anode will have neutral pH!!
For the cathode in this cell, can i use copper ?? |
In a chloro alkali cell the anode chamber remains at 7 however if concentration of NaOH in the cathode chamber is too high about 30% then flow of
sodium ions stop and increase in pH occurs at the anode chamber.
A copper cathode can be used in either a chlorate or chloro alkali cell ofc copper oxides and gunk will form but not too bad.
It is still wise to have a means to measure the pH because if a leak in the membrane occurs due to bad seal then the anode chamber pH will rise which
is not ideal. If you want to avoid that but at the cost of sacrificing efficiency then the Ir-Ta anode is a lot more robust and can handle it even
when the pH gets too alkaline.
[Edited on 10-9-2023 by mysteriusbhoice] |
ok i will have a ph meter on the anode side into an rasberry pi or something and it will kill the cell if it reaches 10. I got a good deal on ir ru
mmo, and i will have to stick with it due to the very high cost of ru ta, 2x or 3x more on aliexpress.
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mysteriusbhoice
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you cannot unpower an Ir-Ru anode while its in solution its better to have a pump drain the electrolyte to another tank for safety. Ir-Ru or even
Ir-Ta without power will destroy it due to it acting as a galvanic cell which will cause damage and dissolution of IrO2.
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