making potassium (per) chlorate

[WSM]

Today I have filtered my small volume of electrolyte due to carbonates precipitating and some titanium bits have settled to the bottom.

The electrode space is only some milimeters at one point and I dont want to risk a short circuit.

Also i tried to use some drops of olive oil to prevent foaming due to boiling. But i have to mention that this only produces a kind of chlorinated soap which is responsible for even more foam on top.

the video was made before filtration.

MOV_1231_Trim.mp4

DSC_1238.JPG

DSC_1237.JPG

edit: I also have to mention that cork works rather nicely to make a tight seal. It gets bleached inside the cell but it holds up the harsh conditions. The yellow color is from the cork i think.

The olive oil i used yesterday was also bleached after some minutes and over night when i did not refill the cell with acidic water the PH drifted to alkaline and the olive oil was converted to a soap.

 

 

I've never added oil of any kind to my cell (the practice sounds odd to me).

 

The narrowest gap I've used is 3 mm (~1/8") and it worked well. To maintain the gap, I use short pieces of PTFE tubing wedged between the electrodes, which also works well.

 

WSM

Edited February 22, 2020 by WSM

[markx]

Is there a specific reason for overdriving that small cell to the aboveseen extremes? I notice that your anode stem is corroding very unhealthy in the process. It hints on the possibility that the extension is made from grade 5 or other alloyed titianium. Alloyed titanium does not passivate to a degree that would prevent it from corroding in a chloride/chlorate bearing electrolyte under positive potential.

I had the same happening in my perchlorate cell and it resulted in noticeable corrosion of the grade 5 anode stem, coupled with a voluminous percipitate of insoluble titanium compounds. Also the soluble alloying elements from the anode stem colored my electrolyte quite noticeably yellow. I suspect the source of your discoloration might also lay in the contamination brought about by the dissolution of the anode extension. I highly doubt the coloration is caused by organic residues leaching from the stopper cork....they would in all probability be oxydised into oblivion by the agressive nature of the cell contents.

 

Having exchanged the anode stem in my cell for one made from CP titanium (pure unalloyed Ti) there was zero reoccurrence of problems with corrosion or electrolyte discoloration. Also the discolored electrolyte batch turned rather pale after about a month of storage in a PE canister, but a hint of greenish yellow could be detected if compared to another pure batch of same nature. In the end I managed to turn the faulty batch into perchlorate without any major problems and the high alkalinity of the perchlorate solution percipitated most if not all of the contaminants as insoluble sludge which could be removed by settling and filtration. It yielded a crystal clear sodium perchlorate solution as a result.

[PTFE]

I've never added oil of any kind to my cell (the practice sounds odd to me).

 

The narrowest gap I've used is 3mm (~1/8") and it worked well. To maintain the gap, I use short pieces of PTFE tubing wedged between the electrodes, which also works well.

 

WSM

Hey WSM. This was just for fun. What could go wrong? Also with this small cell some experiments could be done, since everything is just in a 150ml scale

 

As you may have seen, I made my spacers in the same way like you. =)

 

 

Is there a specific reason for overdriving that small cell to the aboveseen extremes? I notice that your anode stem is corroding very unhealthy in the process. It hints on the possibility that the extension is made from grade 5 or other alloyed titianium. Alloyed titanium does not passivate to a degree that would prevent it from corroding in a chloride/chlorate bearing electrolyte under positive potential.

I had the same happening in my perchlorate cell and it resulted in noticeable corrosion of the grade 5 anode stem, coupled with a voluminous percipitate of insoluble titanium compounds. Also the soluble alloying elements from the anode stem colored my electrolyte quite noticeably yellow. I suspect the source of your discoloration might also lay in the contamination brought about by the dissolution of the anode extension. I highly doubt the coloration is caused by organic residues leaching from the stopper cork....they would in all probability be oxydised into oblivion by the agressive nature of the cell contents.

 

Having exchanged the anode stem in my cell for one made from CP titanium (pure unalloyed Ti) there was zero reoccurrence of problems with corrosion or electrolyte discoloration. Also the discolored electrolyte batch turned rather pale after about a month of storage in a PE canister, but a hint of greenish yellow could be detected if compared to another pure batch of same nature. In the end I managed to turn the faulty batch into perchlorate without any major problems and the high alkalinity of the perchlorate solution percipitated most if not all of the contaminants as insoluble sludge which could be removed by settling and filtration. It yielded a crystal clear sodium perchlorate solution as a result.

Yes there is. I just want to see, how long MMO could survive at high temperature. also it provides the opportunity to fed more salt water into the cell.(not full saturated but acidified to ph 5)

The corosion (on the cathode, picture1238) you mention is a reflection of the underside of the cork. The titanium is doing well (Grade 1). The cathode is the outer ring and the anode is a small sheet in the middle.

 

The floating bits of titanium where from the cathode due to hydrogen embrittlement. Its a really small mesh with 0,5mm wires.

 

The electrolyte was colored after filtration. maybe its from the coffe filter. ( which was not bleached also).

Now its clear again but its full of naclo3 precipitant floating around.

 

 

fun fact: the run was started with a good Computer PSU (30A on the 5Vrail) but after 2 days at 10-14A the PFC filter choke burned out and there was a power failure over night. electrolyte was 5°C and the cell full.(1/3 remains after a night) this showed me, that mmo will survive a powerouttake for several hours. But today There was no significant erosion when I opened the cell for filtration.

 

As you can see, one can use a 200A supply for such a small cell. When I turn down the voltage to the lowest setting, the temperature will settle out at ~80°C and 7A.

The cell will only take an current based of the resistance which is given by the surface of the electrodes and the conductivity of the electrolyte. By using small electrodes you could limit the cell temperature due to limiting the current at an given voltage.

Since I have no workspace and all my equipment is stored by a friends basement I have only the clampmeter available and could not tell you what voltage is used.

Edited February 21, 2020 by PTFE

[PTFE]

yesterday i had to stop the run. more explenations will come later when im back from work.

but one thing is quite interesting

 

This is not the first time this MMO made perc.

The sample of electrolyte is diluted with water (3/4 per volume H2O)

Edited February 22, 2020 by PTFE

[WSM]

Hey WSM. This was just for fun. What could go wrong? Also with this small cell some experiments could be done, since everything is just in a 150ml scale

As you may have seen, I made my spacers in the same way like you. =)

Yes there is. I just want to see, how long MMO could survive at high temperature. also it provides the opportunity to fed more salt water into the cell.(not full saturated but acidified to ph 5)

The corosion (on the cathode, picture1238) you mention is a reflection of the underside of the cork. The titanium is doing well (Grade 1). The cathode is the outer ring and the anode is a small sheet in the middle.

The floating bits of titanium where from the cathode due to hydrogen embrittlement. Its a really small mesh with 0,5mm wires.

The electrolyte was colored after filtration. maybe its from the coffe filter. ( which was not bleached also).

Now its clear again but its full of naclo3 precipitant floating around.

fun fact: the run was started with a good Computer PSU (30A on the 5Vrail) but after 2 days at 10-14A the PFC filter choke burned out and there was a power failure over night. electrolyte was 5°C and the cell full.(1/3 remains after a night) this showed me, that mmo will survive a powerouttake for several hours. But today There was no significant erosion when I opened the cell for filtration.

As you can see, one can use a 200A supply for such a small cell. When I turn down the voltage to the lowest setting, the temperature will settle out at ~80°C and 7A.

The cell will only take an current based of the resistance which is given by the surface of the electrodes and the conductivity of the electrolyte. By using small electrodes you could limit the cell temperature due to limiting the current at an given voltage.

Since I have no workspace and all my equipment is stored by a friends basement I have only the clampmeter available and could not tell you what voltage is used.

 

 

Oh, I see; you're doing an MMO stress test to see how long it runs before failure! Very cool. It would be good to know the limits of our electrodes (if only to avoid their destruction, let alone ensuring their longevity!).

 

I remember Swede talking about wanting to try that long ago, but I never heard if he ever did it.

 

Keep up the good work.

 

WSM

Edited February 22, 2020 by WSM

[WSM]

yesterday i had to stop the run. more explenations will come later when im back from work.

but one thing is quite interesting

DSC_1243.JPG

This is not the first time this MMO made perc.

The sample of electrolyte is diluted with water (3/4 per volume H2O)

 

 

That's interesting, I didn't think MMO had enough oxygen negativity to produce perchlorates. Can you share the particular details of your setup and the materials used? What type of MMO, etc.?

 

Thanks. That would be good to know, plus also to see if your results are repeatable (by others).

 

If you don't want to share the details publicly, you can PM me.

 

WSM

Edited February 22, 2020 by WSM

[Pyrophury]

maybe, when the run is finished i try out if silicone sealant is responsible for MMO-failure by adding some fresh silicone to a new portion of electrolyte.

 

I think it was the silica in the silicone grease that caused my MMO anode to fail.

 

I've been running my cell with the new MMO anode for 130 Hrs at ~25A. The current has fluctuated slightly, dropping overnight as the ambient temperature drops, otherwise it's been very consistent. I should need to run for at least another 5 days (assuming 50% CE) until the chloride level drops to 100g/l, but looks better so far...

[WSM]

I think it was the silica in the silicone grease that caused my MMO anode to fail.

I've been running my cell with the new MMO anode for 130 Hrs at ~25A. The current has fluctuated slightly, dropping overnight as the ambient temperature drops, otherwise it's been very consistent. I should need to run for at least another 5 days (assuming 50% CE) until the chloride level drops to 100g/l, but looks better so far...

 

 

Congratulations. It sounds like the problem is solved.

 

WSM

[Pyrophury]

I fabricated a pair of 12" long straps and welded them to my electrodes over the weekend.

 

 

I wasn't able to weld the strap to the lead dioxide anode where I originally wanted, to the horizontal bar, even after I'd sanded the area smooth it just would not weld at all. So I had to mount it further up the existing strap where the oxide layer was thinner and I was able to sand it off.

 

Small beads of lead began escaping from the flattened end of the tube when I welded on the anode, even though I tested it for air-tightness and non leaked during filling. I hope this won't be a problem when in use?

[PTFE]

 

 

That's interesting, I didn't think MMO had enough oxygen negativity to produce perchlorates. Can you share the particular details of your setup and the materials used? What type of MMO, etc.?

 

Thanks. That would be good to know, plus also to see if your results are repeatable (by others).

 

If you don't want to share the details publicly, you can PM me.

 

WSM

 

Hey WSM.

This MMO is an mesh which was used in a galvanisation process to reduce the current density on the soluble tin-anodes. I do not know what coating they have.

 

The cell was started with saturated brine and i added nacl to the cell after one day runtime and 1.5days before i had to stop the run.

Also when i had to refill the cell i used acidified salt water which was not ful saturate but I did not weigh out the nacl which was used.

 

 

I had to stop because the cork started to degrade and the cathode eroded at a high rate resulting in titanium bits floating in the cell.

An EPDM stopper is on the way and i will restart the cell with the new purpose to see how this mmo works out in perc. production.

 

I think the high temperature of ~110°C could also have an impact.

 

 

I've boiled down the electrolyte to dryness, resulting in a weird slurry which seemed not to dry out complete.

After adding a litte water i put everything in the fridge to ppt out something but i only get little tiny needles unable to get pictures from.

The electrolyte is still a liquid at -27°C.

 

I've made some pictures of the electrodes and you can see, i have got the same white precipitant on the anode as others.

It is insoluble in HCL and H2SO4 but i got it whiped of with a brush and warm water.

 

 

 

[PTFE]

I fabricated a pair of 12" long straps and welded them to my electrodes over the weekend.

 

 

I wasn't able to weld the strap to the lead dioxide anode where I originally wanted, to the horizontal bar, even after I'd sanded the area smooth it just would not weld at all. So I had to mount it further up the existing strap where the oxide layer was thinner and I was able to sand it off.

 

Small beads of lead began escaping from the flattened end of the tube when I welded on the anode, even though I tested it for air-tightness and non leaked during filling. I hope this won't be a problem when in use?

 

This looks amazing

 

 

 

[WSM]

I fabricated a pair of 12" long straps and welded them to my electrodes over the weekend.

I wasn't able to weld the strap to the lead dioxide anode where I originally wanted, to the horizontal bar, even after I'd sanded the area smooth it just would not weld at all. So I had to mount it further up the existing strap where the oxide layer was thinner and I was able to sand it off.

Small beads of lead began escaping from the flattened end of the tube when I welded on the anode, even though I tested it for air-tightness and non leaked during filling. I hope this won't be a problem when in use?

One question, what's the wall thickness of your Ti tubing?

 

WSM

[WSM]

Hey WSM.

This MMO is an mesh which was used in a galvanisation process to reduce the current density on the soluble tin-anodes. I do not know what coating they have.

The cell was started with saturated brine and i added nacl to the cell after one day runtime and 1.5days before i had to stop the run.

Also when i had to refill the cell i used acidified salt water which was not ful saturate but I did not weigh out the nacl which was used.

I had to stop because the cork started to degrade and the cathode eroded at a high rate resulting in titanium bits floating in the cell.

An EPDM stopper is on the way and i will restart the cell with the new purpose to see how this mmo works out in perc. production.

I think the high temperature of ~110°C could also have an impact.

I've boiled down the electrolyte to dryness, resulting in a weird slurry which seemed not to dry out complete.

After adding a litte water i put everything in the fridge to ppt out something but i only get little tiny needles unable to get pictures from.

The electrolyte is still a liquid at -27°C.

I've made some pictures of the electrodes and you can see, i have got the same white precipitant on the anode as others.

It is insoluble in HCL and H2SO4 but i got it whiped of with a brush and warm water.

DSC_1247.JPG DSC_1248.JPG DSC_1258.JPG DSC_1261.JPG

DSC_1265.JPG DSC_1272.JPG DSC_1273.JPG DSC_1274.JPG

DSC_1275.JPG

 

 

I wonder if a Viton or Teflon sheet between the stopper and the interior of the cell would help prevent damage to the stopper at those temperatures?

 

Let's see how the EPDM works out...

 

WSM

Edited February 24, 2020 by WSM

[Pyrophury]

One question, what's the wall thickness of your Ti tubing?

 

WSM

 

1mm wall thickness. I am only using a converted microwave oven transformer to do the welding, it has proved adequate so far though.

[WSM]

1mm wall thickness. I am only using a converted microwave oven transformer to do the welding, it has proved adequate so far though.

 

I had a similar problem using thin walled titanium tubing. I had to replace the tubing with thicker walled tubes.

 

The thin tubing is weaker at the welds and prone to crack and leak.

 

The thicker Ti tubing handles heat forging and spot welding without as many problems, in my experience.

 

WSM

Edited February 24, 2020 by WSM

[PTFE]

I wonder if a Viton or Teflon sheet between the stopper and the interior of the cell would help prevent damage to that stopper?

 

Let's see how the EPDM works out...

 

WSM

I think if natural cork is used it could be quite suitable but since mine was a agglomerated cork it did not hold up well especially when chlorate concentrations got higher and the salt creep got more remarkable.

 

To ensure a good seal it would be easier to manufacture a stopper out of ptfe directly instead of trying to seal up any throughhole to prevent gas lekage into the cork.

 

 

I think the epdm will hold up to a certain extent but looking at resistance tables for Cl² in water it does not look very promising :/

PTFE

Edited February 24, 2020 by PTFE

[WSM]

I think if natural cork is used it could be quite suitable but since mine was a agglomerated cork it did not hold up well especially when chlorate concentrations got higher and the salt creep got more remarkable.

To ensure a good seal it would be easier to manufacture a stopper out of ptfe directly instead of trying to seal up any throughhole to prevent gas lekage into the cork.

I think the epdm will hold up to a certain extent but looking at resistance tables for Cl² in water it does not look very promising :/

PTFE

If you could find or fabricate a stopper of Viton B, that should work well. A stopper of PTFE would probably be easier to make.

 

WSM

[WSM]

I fabricated a pair of 12" long straps and welded them to my electrodes over the weekend.

 

I wasn't able to weld the strap to the lead dioxide anode where I originally wanted, to the horizontal bar, even after I'd sanded the area smooth it just would not weld at all. So I had to mount it further up the existing strap where the oxide layer was thinner and I was able to sand it off.

Small beads of lead began escaping from the flattened end of the tube when I welded on the anode, even though I tested it for air-tightness and non leaked during filling. I hope this won't be a problem when in use?

 

 

Nice work on the electrodes and tubular leads.

 

Something I learned over the years of making my own electrodes and cells; If you move the tubular leads to the edge of the square or rectangular electrode plates (especially if you're using compatible [PTFE or PVDF] compression fittings to hold the leads in the cell lid, per Swede's instructions), you can adjust the electrode gap simply by twisting the tubes in or out while tightening the fittings, AND you won't crowd the fittings on the lid.

 

This is an example of what I'm describing

 

Swede liked my idea and moved the leads to the extreme edges of the electrodes for the maximum adjustability. If you tape cards to pencils and experiment on adjusting the gap between the cards (electrodes in the actual setup), you'll see it the way Swede did.

 

It's important to tighten the compression fittings very well, and to use PTFE tubing spacers help to prevent electrical shorting of the electrodes, as well as maintaining the gap.

 

WSM

Edited February 25, 2020 by WSM

[WSM]

I should mention, considering your experience with the LD anode, the lead should stay where you placed it. The lead on the cathode plate, though, could be placed at the edge (rather than centered) to help prevent crowding on the lid of the cell (as per my previous post).

 

Keep up the good work.

 

WSM

Edited February 25, 2020 by WSM

[Andead]

Is it possible to produce perchlorate with the 5volt rail from an ATX computer power supply?

[Pyrophury]

I think I'm coming to end of the run, the current has dropped from around 30A to 17A in the space of 24 hours. It's been 9 days of the estimated 8-10 day run time.

 

If that's the case then the chlorate concentration should be about 400g/l with about 100g/l of chloride left (I started with 330g/l of chloride). This amount of dissolved chlorate isn't enough to precipitate out, so I want to add more chloride (100g/l) to the brine and continue the run until the chlorate concentration increases.

 

I've added 100g of chloride (total) to the cell, but so far it doesn't show any signs of going into solution. I thought this would save me the trouble of having to boil off a third of the volume of water, only to add more saturated chloride solution. But it looks like I'm going to have to do this anyway... the disadvantage of a closed cell.

[WSM]

Is it possible to produce perchlorate with the 5volt rail from an ATX computer power supply?

 

The short answer is yes. Those who use a computer power supply say to combine all the +5Vdc leads together and all the return (-) leads together, plus add a resistor in parallel to keep the supply switched on.

 

There's more to it than this but I'll defer to those who use computer power supplies to fill in the particular details.

 

WSM

Edited February 26, 2020 by WSM

[Andead]

The short answer is yes. Those who use a computer power supply say to combine all the +5Vdc leads together and all the return (-) leads together, plus add a resistor in series to keep the supply switched on.

 

There's more to it than this but I'll defer to those who use computer power supplies to fill in the particular details.

 

WSM

Thanks alot WSM for your speedy response.

[WSM]

I think I'm coming to end of the run, the current has dropped from around 30A to 17A in the space of 24 hours. It's been 9 days of the estimated 8-10 day run time.

 

If that's the case then the chlorate concentration should be about 400g/l with about 100g/l of chloride left (I started with 330g/l of chloride). This amount of dissolved chlorate isn't enough to precipitate out, so I want to add more chloride (100g/l) to the brine and continue the run until the chlorate concentration increases.

 

I've added 100g of chloride (total) to the cell, but so far it doesn't show any signs of going into solution. I thought this would save me the trouble of having to boil off a third of the volume of water, only to add more saturated chloride solution. But it looks like I'm going to have to do this anyway... the disadvantage of a closed cell.

 

 

 

This is a sodium chlorate cell, right?

 

If so, the product is more soluble than the chloride, so you can either add more chloride and keep running it till the concentration of chlorate is enough to force it out of solution, OR you can chill the electrolyte to drop out a portion of the chlorate, recharge the electrolyte with more chloride and run it more.

 

These are two ways to accomplish the same goal: to force the sodium chlorate out of solution.

 

WSM

Edited February 26, 2020 by WSM

[WSM]

Thanks alot WSM for your speedy response.

 

 

You're welcome, but please note the correction I made to my comment above. The resistor needs to be parallel to the output (not in series with it). It provides a load which will keep the supply switched on.

 

You may want to connect the two bundles of 5 Vdc leads to positive and negative Buss bars for convenience in feeding the electrode leads (bolting them solidly is best).

 

Good luck.

 

WSM