making potassium (per) chlorate

[WSM]

I think the topic of contaminant removal deserves more attention.

 

When I started my sodium chlorate experiments, it was because of the lack of availability to me of pure material to use

for the production of sodium perchlorate which I could easily convert to potassium perchlorate.

 

Before I started my new setup, I made a large quantity of NaCl brine. For this, I acquired a good amount of low cost, sea salt, water softener salt.

 

When I dissolved this material, right away I saw a problem. Not only did I see the normal rust chunks and small pebbles, but worse was a lot of fine, beige-colored silt in the bottom of the brine tank.

 

After filtering out the obvious debris, I determined to chemically treat the clear brine I had left, before running it in my large cell.

 

I made a 1N solution of sodium carbonate and added roughly 350ml to each 5 gallon bucket full of clear brine (about 18 liters in each bucket), which immediately turned milky white.

 

After waiting overnight, the fine white precipitates settled to the bottom of the buckets. I next carefully decanted the purified clear brine off the top of the sediment and then vacuum filtered the residue.

 

Next, I tested the pure brine and found it to be quite alkaline, so I treated it with dilute hydrochloric acid till it was neutral to slightly acid. Now my brine was pure enough to run in the sodium chlorate cell.

 

The sodium chlorate crystals harvested from the first run were very clear and nice. I attribute their appearant purity to the refining of the brine prior to running the cell.

 

I feel it will only improve the quality of the potassium perchlorate I hope to make if I take the extra steps to purify the potassium chloride brine I plan to use in the conversion of sodium perchlorate solution to the potassium salt.

 

To facilitate the potassium chloride purification step, I acquired a quantity of high purity potassium carbonate.

 

The next step will be to filter and treat my potassium chloride brine, then filter out any precipitated contaminants before neutralizing the resulting clear brine.

 

More to follow...

 

WSM

Edited May 27, 2019 by WSM

[WSM]

I see on Ebay, that laserred has MMO mesh and CP titanium sheet material listed, besides a lot of machining tools.

 

I've used the MMO anode material from laserred for over a decade now, and it works well in making chlorates.

 

It's not new material but seems to have a lot of life left in it, if treated properly.

 

I'm not associated with laserred in any way, other than as a satisfied customer.

 

WSM

[TomasBrod]

There is a new seller on Ebay selling MMO and Lead dioxide anodes, feanor.forges. His location in Europe (france) can be advantageous for other european members. He is also active on Amateurpyro discord under the nick Feanor. The prices are not as good as lassered's offerings. However he plans selling a set of electrodes that is already glued into a container lid maybe even with corrosion-resistant connection attached in the future.

For posterity, I am relaying this information from Discord.

[WSM]

It's good to see multiple options for electrodes.

 

The electrode of primary interest is the anode, of course, and cathodes can be fabricated from raw CP titanium sheet stock.

 

I'm glad that he also handles lead dioxide anodes. There is mention of using the LD anode to run sodium chloride all the way to sodium perchlorate. I haven't tried that so I don't know if or how well that would work.

 

The only source I've read describing that process successfully, utilized sodium fluoride as a catalyst, so the anode they used was lead dioxide on a graphite substrate (which they made themselves).

 

If the same system is attempted with a titanium substrate LD anode, it will fail due to the fluoride attacking the titanium, destroying the electrical conductivity of the electrode, let alone the destruction of titanium cathodes (depending on the degree of cathodic protection afforded by the current during operation).

 

I'll have to learn more of the basis behind their claims before I can know for sure if they're correct.

 

We'll see...

 

WSM

[mabuse00]

 

I've used the MMO anode material from laserred for over a decade now, and it works well in making chlorates.

How much lifetime / amperehours could you squeeze out of that material, under typical circumstances?

[Arthur]

Electrode life is mostly determined by the user! At the recommended current density it will last for years, double the current density and it could die in days.

[WSM]

How much lifetime / amperehours could you squeeze out of that material, under typical circumstances?

 

I don't know, but Arthur's right about you being in control of its use.

 

I've only made periodic runs with my cells, and never run one till the anode failed.

 

If you do the math, taking into account the power supply capacity as well as the anode area, you can maximize the life of your electrodes and possibly get years of use out of them.

 

The maximum recommended current is 0.3 A per square centimeter. Less than that is okay, but will take longer to produce the chlorate.

 

WSM

Edited May 30, 2019 by WSM

[Arthur]

There is the current to produce chlorate at a reasonable rate then there is current to keep the cell hot for the reaction to prefer chlorate rather than less oxidised species, then there is more current where flecks of black MMO can be seen circulating in the liquor when the electrode is dying quickly. The art and science of running a cell is to run hard enough to prefer chlorates rather than bleach being produced but comfortably short of breaking the MMO off the titanium. The heat from the cell causes it's temperature to rise above ambient, cooling may be needed in hot climes.

 

If you keep to WSM's indicated 0.3a/cm² then the MMO should last 10+ years, double that current then this may go down to 10 minutes.

[WSM]

My chlorate cells always seem to generate heat while they run, though I've never seen them run either too hot or too cold.

 

Usually, my cell liquor starts out with a strong smell of bleach, which remains as the run continues and later potassium chlorate crystals drop out of solution as the chlorate concentration increases.

 

I believe that the liquor first forms hypochlorite ions, then progresses to mixed chlorite and hypochlorite ions, and next they're forced into chlorate ions. The entire process is driven by the current though proper electrodes, and given the right conditions.

 

With the potassium chlorate cell, this works simply and quite well. In a sodium chlorate cell, the system works differently due to the opposing physical natures of sodium versus potassium chlorate and perchlorate salts.

 

WSM

Edited May 31, 2019 by WSM

[PTFE]

This is true.

 

If you take this route, you may want to consider a closed loop system, using a pump plus a radiator and fan cooling system to dissipate heat.

 

I'm thinking of something similar to those used to water-cool computers. The various components are available on Ebay and can be had for bargain prices if you shop carefully.

 

Can you show us what you have in mind, either by photo or drawings? It sounds interesting.

 

WSM

Hey WSM

Nice to see, that the per/chlorate process is still in development and improving.

I've moved around for 3 times since December 2018 and now i need to find a place for my workspace. But I'm fortunate to present my high current system this maybe next year.

 

Arthurs post refers to my 300A/600A Systems that im planning since over 2 years now.

My initial 50A and 100A cells I've showed earlier where only to learn about the process and to get a look at the conditions and the cooling power needed when using relativley small volumes.

 

I got myself a 10L PTFE Tank (inside:h=500mm /d=230mm) which will be used as electrode chamber and my old 4,5L PTFE container will be used as a reservoir.

With water pumped through a 4x6mm PTFE tube the electrolyte will be cooled inside the 4,5L tank. This was used before for my 100-120A runs to keep the electrolyte just at 88-90°C

I'm thinking of many 8x10mm PVC tubes closely spaced running from top to the bottom of the tank to provide even more cooling.

The water will be rainwater from a 500l garden supply which will be pumped in another tank in one run to provide enough cooling for maybe 1 Day. For reducing heat in the second Tank, i plan to build a waterslide out of 1m long stainless steel with sheets inbetween to increase the surface area. When the 500l tank is empty, the water in the second tank is hopefully cool enough to be pumped back through into the first 500l Tank.

The filtration of the cooling water is also critical to not jam the cooling pipes with dirt.

Edited June 1, 2019 by PTFE

[WSM]

Hey WSM

Nice to see, that the per/chlorate process is still in development and improving.

I've moved around for 3 times since December 2018 and now i need to find a place for my workspace. But I'm fortunate to present my high current system this maybe next year.

Arthurs post refers to my 300A/600A Systems that im planning since over 2 years now.

My initial 50A and 100A cells I've showed earlier where only to learn about the process and to get a look at the conditions and the cooling power needed when using relativley small volumes.

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I got myself a 10L PTFE Tank (inside:h=500mm /d=230mm) which will be used as electrode chamber and my old 4,5L PTFE container will be used as a reservoir.

With water pumped through a 4x6mm PTFE tube the electrolyte will be cooled inside the 4,5L tank. This was used before for my 100-120A runs to keep the electrolyte just at 88-90°C

I'm thinking of many 8x10mm PVC tubes closely spaced running from top to the bottom of the tank to provide even more cooling.

The water will be rainwater from a 500l garden supply which will be pumped in another tank in one run to provide enough cooling for maybe 1 Day. For reducing heat in the second Tank, i plan to build a waterslide out of 1m long stainless steel with sheets inbetween to increase the surface area. When the 500l tank is empty, the water in the second tank is hopefully cool enough to be pumped back through into the first 500l Tank.

The filtration of the cooling water is also critical to not jam the cooling pipes with dirt.

 

Fascinating!

 

I look forward to seeing your progress and I'm ready to offer any suggestions you may need or want, in overcoming any problems you encounter with design or concepts.

 

It sounds like you have a good grasp of many technical aspects of the project, but if I can help in some way, it would be my honor to contribute with any problem solving suggestion or thought.

 

On the other hand, if I may ask you for details of certain particular portions of your project which could assist me in my efforts, would that be okay?

 

Thanks for sharing what you've accomplished so far. I like how it's coming along...

 

WSM

Edited June 2, 2019 by WSM

[PTFE]

Fascinating!

 

I look forward to seeing your progress and I'm ready to offer any suggestions you may need or want, in overcoming any problems you encounter with design or concepts.

 

It sounds like you have a good grasp of many technical aspects of the project, but if I can help in some way, it would be my honor to contribute with any problem solving suggestion or thought.

 

On the other hand, if I may ask you for details of certain particular portions of your project which could assist me in my efforts, would that be okay?

 

Thanks for sharing what you've accomplished so far. I like how it's coming along...

 

WSM

My progress will be very slow, but it will keep on. (see the 300A PSU some pages ago)

Please feel free do share all your thoughts that will come up, because you may see problems i never thought about.

My tecnical facination comes from my job as electrical engineer. And after 1 year in a galvanic plating facility and many years in facilitys with chemical equipment, i like to built it up like the industry does it.

Please feel free to ask any kind of question you may have.

 

One thing im concerned about is the output of Hydrogen. Im thinking of an strong fan blowing air inside the cell out through the venting hose to reduce the criticality of the mixture of H2+O.

 

[Arthur]

The hazard with hydrogen is build up in closed volumes. Hydrogen will naturally rise in air and if you give it enough space it will rise out of the building.

[WSM]

One thing im concerned about is the output of Hydrogen. Im thinking of an strong fan blowing air inside the cell out through the venting hose to reduce the criticality of the mixture of H2+O.

 

 

All of the hydrogen removal systems I've employed so far have been passive, rather than active. Hydrogen's explosive nature is released with very low input energy.

 

The only "active" method of removal I've ever considered involved using a fan remotely to create an upward draft above the cell without any possibility of ignition by heat, spark (electric or static) or flame.

 

To date, the safest method I use it to put an adequately large vent at the highest point of the cell and run the system outdoors, nowhere near an ignition source.

 

Hydrogen is buoyant enough to always rise up and away from my workspace. The trick is to carefully design so you avoid creating any place that can allow freed H2 from welling, causing a potential explosion hazard.

 

Think three dimensionally; look up and see if there's any possible problems with the space you want to work in, and design the area for prevention of those problems.

 

I hope I'm not rambling, but giving you the idea of being as safe as possible when removing a hazard like this.

 

WSM

Edited June 2, 2019 by WSM

[WSM]

A bigger problem I encountered with a larger cell running at higher temperatures, was saline spray coming out with the hydrogen through the vent.

 

Several attempts to alleviate the problem failed before I used a condensation collector inline with my vent exhaust.

 

The most successful setup involves a thinwalled vinyl tube running from the cell's exhaust port, up and over in a vertical arc, down into a clear jar (pliable polymer is best, maybe thin PET plastic) to collect vaporized mist and salt spray as a liquid, allowing the dryer hydrogen to escape through a vent tube in the top of the condenser bottle.

 

Most of the condensation occurred in the thin walled vinyl tubing, allowing the saline liquid to reflux back into the cell. Whatever liquid that got past the vinyl tube collected in the jar and the hydrogen went safely up and out of the collection jar through a thin PVC vent pipe (on top of the collection jar) with a T-fitting on the top end to prevent rainwater getting in.

 

I can try to find a photo of this part of the system when I return home (I'm visiting family and don't have access to my files now), and post one to show how it worked.

 

WSM

Edited June 2, 2019 by WSM

[WSM]

I can try to find a photo of this part of the system when I return home (I'm visiting family and don't have access to my files now), and post one to show how it worked.

WSM

I've been home for nearly a week, but I have a serious problem. My computer is failing and unless I can move all my data and photos to a new system (yet to be acquired), I may lose years of research and unpublished information.

 

Much of my work is backed up on external drives, but some of my more recent notes and thoughts have not been saved.

 

I'll see what can be done...

 

WSM

Edited June 14, 2019 by WSM

[TomasBrod]

After a long break I am again getting myself into electrolysis. I do not want to use the electode from lassered, as it failed twice on me so I spent some time asking Chinese companies if they could make me a custom set of electrodes. I succeeded and they promised me a set with tubular titanium leads ala Swede at reasonable price. That is great, because it means I will not have to hunt for titanium metal stock and bother other people to spot-weld it for me. I will lead copper cables down the tubular lead and fix them there with some molten solder (or zinc). For power supply I rebuilt another old computer PSU and augmented it with adjustable constant current mode up to 20 A. For salt, I have been purifying agricultural grade (red) potassium chloride using thermal recrystallization method. I do not have the electrodes yet, but I hope to at least start building the reaction chamber before they arrive. And that is what I am hoping to get input from you dear forum members on. I determined that liquid volume of 4 liters (or more) will be used. Glass jars of the desired volume are cheaply, even freely, available here. However, they lack plastic lids and the threads to screw lid on. Another option, which I am more inclined to, is to assemble the reaction chamber from PVC sewage pipe. Glueable end plugs for those are available and can serve as a cell bottom. But I am stuck on the lid. Obviously, I can use the same plug for lid, it would prevent access. I want to keep it airtight, so some kind of threaded adapter and screw on lid with a gasket. Do you have any suggestion of what can I use?

[Arthur]

Among interesting plastic jars I've seen are 4 litre jars with lids for holding fruit juice in the door of a fridge, or large jars for holding breakfast cereal in a breakfast kitchen.. Both were polypropylene and should be good for months but not years..

[TomasBrod]

The lid (and throat it is covering) has to be big enough to pass the electrode assembly, which is going to be 4 cm wide.

Thanks to Arthur's suggestion I looked for plastic jars of sorts and indeed there are some of suitable dimensions. But I am worried about the gasket rubber deteriorating.

Attached is a illustration of the container.

Edited August 6, 2019 by TomasBrod

[Arthur]

All economy containers will be Chinese so the gasket material could be good or could be less so -no hope of finding without trying.

 

Like I said above at the price I found them ( about £/$/Euro 5!) if they last three months that's OK to me.

[TomasBrod]

if they last three months that's OK to me.

I do not care as much about they lasting, but what the decomposition products are. If the plastic releases some chemical that attacks or binds to the electrodes, that would be bad.

[WSM]

I do not care as much about they lasting, but what the decomposition products are. If the plastic releases some chemical that attacks or binds to the electrodes, that would be bad.

Try it and see. There's no reason to worry before you know whether or not it even works.

 

I would use the glass jars if they're big enough. The lid doesn't need to seal, but it'll help prevent salt creep if it does. The vent will keep the internal pressure at one atmosphere.

 

WSM

[GrassyKnollShooter]

It can be synthesized very easily but you don't appear to have any chemistry background.

 

You're playing with fire my friend.

[WSM]

...you don't appear to have any chemistry background.

 

You're playing with fire my friend.

Considering this is the AMATEUR PYROTECHNICS AND CHEMISTRY forum, that's a given.

 

A chemistry background isn't required, but it certainly helps.

 

WSM

Edited September 2, 2019 by WSM

[Arthur]

Several people on here have lots of higher education and letters after their names and lots of industrial experience in electrochemistry, others have lots of very relevant private study and may make very important contributions to the discussion.