making potassium (per) chlorate

[NightHawkInLight]

Ooo cool, everything from paris green to wet towel dispensers

 

I might have to get into this whole chlorate production thing when I next have the time. Your MMO is pretty tempting Swede. Maybe when the next check rolls in.

[Arthur]

One guy in the UK used to run a perc cell and most of his control was via the current setting. Turn the current up and things got hotter so the call contents would dissolve easily and lumps would go into solution! Turn the current down and the temp went down so things started to precipitate, when the perc content was sufficient the perc would crystalise out first. So he just cooled the cell syphoned the perc off the topped up and started again, current up chloride in and electrolyse for a week at 50 - 80 amps.

 

His cell was about a litre, but it was on the side of a 50 litre reservoir tank so there was enough solution circulating!

[Swede]

I like that concept and messed around with a 2-chambered system, but it was a disaster... as the hot liquor exited the electrode chamber to travel to another chamber for collection, it cooled very rapidly, and the crystals that formed jammed the tubing hopelessly.

 

I think the technique you describe has a lot of potential, but the only thing that makes me hesitate is the thought that lowering the temperature to force crystallization would also crystallize a significant % of the KCl, which might contaminate the product.

 

I've compromised - what I do now is make a saturated KCl solution at some heat, let it cool to room temp (which drives out a bit of KCl as crystals), and from there it goes into the cell. If the temperature at the start was 20 C, I can be confident that so long as the temp is > 20 C, then any crystals that form are chlorate, not chloride.

 

The other methodology that I thought showed promise was to make use of those huge nuggets of KCl to actively recharge while the cell is operating. From the big KCl sack, select only the largest nuggets, many the size of walnuts or pecans. Install them in a mesh sack or some other container that allows circulation through the nuggets, but contains them. As the hot liquor contacts the nuggets, a certain % of KCl will dissolve and enter the solution for electrolysis. When done, the KCl nuggets will be either gone, or greatly reduced.

[Swede]

One of my goals has always been to figure out a way to use round Ti tubing rather than sheet for hanging electrodes. Cutting a thin slot in any decent thickness of plastic sucks, and the joint inevitably leaks, is wobbly, and it is hard or impossible to remove the electrode for maintenance. A few months back, Tentacles and I were tossing ideas back and forth on what we called the "bucket cell adapter," which would be a set that would consist of one (or two) disks of PVC, a viton o-ring, perhaps some Ti bolts, and a method to mount electrodes, with the whole thing being used to turn a typical hardware store HDPE bucket into a good cell. Once the bucket wears out, move the adapter to a new one.

 

I came up with a labor-intensive and somewhat specialized solution to a part of the adapter concept - the use of a round Ti shank and a PVDF compression fitting to deliver the juice to the anode.

 

http://www.5bears.com/perc/rst04.jpg

 

http://www.5bears.com/perc/rst05.jpg

 

There was enough info to make a blog about it, if anyone is interested. Round shank anodes

 

Again, this is chlorate cell 401 rather than 101. There is no reason flat straps cannot be used, but I wanted something a bit easier in use.

[Bonny]

It seems that one of the fittings I used (for my vent tube) must have been nylon... I added some HCL last night to try and lower the ph and I heard a clunk, and saw my vent tube hanging loose. The lower portion of the(compression) fitting had dissolved! I now have the teflon (I hope) seal somewhere in the cell. Nasty chlorine gas cloud from that.In any case I couldn't get a reading with my litmus paper anyway, I think the hypochlorite must have bleached it as mentioned by Wouter Visser.

Anyway, I guess I'll leave out any attempts at ph control and just let the cell run.

[WSM]

I like that concept and messed around with a 2-chambered system, but it was a disaster... as the hot liquor exited the electrode chamber to travel to another chamber for collection, it cooled very rapidly, and the crystals that formed jammed the tubing hopelessly.

 

I think the two chambered system still has merit. If the liquor were kept warm till it reached the crystal forming chamber, I believe it would work. Perhaps a hot water jacket or a strategically placed heater would help keep the liquid hot enough to prevent crystalization till it reached the second chamber. Keeping a short distance with larger plumbing between the two chambers seems prudent. There are many ways to approach this. What does industry do?

[Arthur]

The two pot design works if the circulation is forced by a good pump that doesn't clog and/or the connecting tubes are short and wide enough -like 1 - 2 ins Bore!

[Swede]

I agree, I think you'd need a centrifugal pump, probably one rated for sediment, as a peristaltic pump is very sensitive to particulates. I'm concerned, though, that even heavily insulating the piping wouldn't solve the problem entirely, because as the chlorate concentration rises, it eventually reaches saturation at a particular temperature, and even a degree or three less forces crystallization. Once the seeds form, they grow, and grow, and jam the plumbing unless the bore is exceptionally wide and the flow rate high. The latter is a problem, because if the flow rate is too high, you'd have a very similar temperature between the two cells.

 

When I first started my 2-celled rig, the plan was for the electrode chamber to be at about 60 to 80 C, and the big collection chamber to be at least 30 degrees cooler. Crystals were supposed to dump only in the collection chamber, where they'd be harvested. I set the pump for a slow rate, and the delta T between the two was perfect. It ran that way for 2 days before the jamming started.

 

When I went back to one big cell, the KISS principle shined, and it was tough to argue with 3 kilograms of oxidizer scooped out of it with little fuss. Recharged, and away it went on another run. I love complexity, but sometimes KISS simply rules, and a large volume overcomes many objections. If I were to make it any more complex, I'd lean in the direction of a recharging cannister that would add chloride, rather than a specialized harvesting chamber. Normal saturated KCl will produce chlorate to occupy about 1/4 to 1/3 the volume. With a chloride recharging mechanism, that 1/4 could be turned into 3/4 full, which would be (for my 24 liter cell) maybe 10 kilos of KClO3 before harvesting.

 

The idea is to minimize the "down" time, and I think that can be more easily done with a chloride recharger rather than a continuous harvest system. The latter would be really elegant but there are definitely some serious engineering challenges to overcome, assuming potassium is used from the start. A two-celled sodium rig would be pretty easy, but to me, the hassle of conversion to potassium and cleaning of the sodium from the product makes that a second-place option.

 

Areas that need work for hobby cells:

 

- Reduction of salt creep

- electrode mounting

- durability of materials

- chloride measurement and recharging

- user-friendly pH control

- Processing of product; can it be done so that no recrystallization is needed?

- a big one is stirring. Mechanical is the way to go, bubbling is a dead end due to clogging.

 

And of course, the ultimate goal to me is perchlorate. Electrolysis of the chlorate to perc with lead dioxide is very close. The data rig is waiting. It's going to be an interesting fall!

 

I've been working on a really fat document that compiles everthing I've learned with stuff from Wouter's site and dann2, and some of the correspondence I've done with Tentacles. I'm trying to make it a user guide, not a theory paper. It's at 30 pages now, and I'm guessing it'll be close to 75 when finished. It'll be available to anyone interested when I'm done.

[Ralph]

i had this idea (i know that most times that people say this you brase your self for some stupid idea but here i go)

 

 

the electrolysis of sodium chloride in chlorate production is more efficient than the electrolysis of potassium chloride

 

also using sodium reduces ware on the electrodes so in a MMO cell that means longer life of your anode or in a graphite cell less graphite to remove

 

but sodium chlorate is more soluble than sodium chloride making processing interesting

 

the product people in many cases are after is potassium chlorate

 

so i think you could probably have the best of both worlds by making your original solution 50 50 with potassium and sodium chloride than your resupply solution should just be just potassium chloride as the crystals forming which can than be easily collected will be removing only the potassium ions

 

what are peoples thaughts

[50AE]

In my opinion it's a pain to remove the sodium contamination, so I prefer using directly potassium chloride, because the purification is much simpler.

[Ralph]

i think using this method the residual sodium in the chlorate would hopefully be minimal

[Swede]

Ralph, you and Arthur (and many others) are of the same mind, use sodium in some quantity. I have never even tried it. It might be the way to go. I just dislike the added step of conversion, and it is hard enough to clean up as it is. The thing is, sodium perchlorate is freakishly soluble compared to potassium, so if a method can be engineered to proceed from sodium chloride to sodium perchlorate with no intermediate, and if you can titrate or otherwise determine the exact amount of sodium perchlorate in the liquor, by mixing up very slightly less potassium chloride (on a molar basis), when you mix the two, you will get a blizzard of potassium perchlorate crystals. What will be left behind though will be an odd hash of Na+ and K+ ions, and a mix of mostly chloride, residual chlorate, and some perchlorate. What do you do with this liquor? I think it would be easy to lose track of what's in there without a lot of quantitative work.

 

It's harder with just chlorate, as potassium chlorate is still reasonably soluble, but much less so than the sodium.

 

From my own notes:

 

Salt---0 deg---100 degrees

 

KCL-----238-----567

KClO3--71-------570

KClO4-- 8-------218

 

NaCl----357-----391

NaClO3--790---2300

NaClO4--2090--2840

 

What an odd phenomenon. As each is further oxidized, they go in opposite directions in terms of solubilities. But the spread between 0 degrees and 100 degrees for the potassium makes it easier to recrystallize and purify. Anyway, it is an interesting problem, and I'd love to see someone do some work with sodium.

[Arthur]

My understanding of the chemistry is that the K and Na chlorides can both, fairly easily be electrolysed to ClO3. However only the Sodium salt can be electrolysed to perchlorate.

 

In the UK chlorate is almost unused, very few people use chlorate stars or H3. It's only significant use is for DIY igniters using dark flash as their prime. And with their small amount of comp the market size is small, no microscopic! I seriously doubt I'll get through 100g of Chlorate this year but I'm thinking of 10kilos of perc.

 

UK desire is to have a good supply of perc! So with the present supply situation a few people will have a drum pf perc and split it out.

 

If I had to make an oxidiser I would consider a chloride to chlorate cell using MMO electrodes and Sodium as Cation. This I would then take through to Perchlorate possibly using Pt plated Ti electrodes. This I would then mix with KCl to ppt out potassium perchlorate.

 

In the UK KCl is not available as water softener salt, only as lab reagent for a silly price. Here softener salt is only available in the sodium salt form

 

Added

If I go through with this I shall electrolyse the sodium salt and precipitate out the less soluble K salt leaving the cell reloaded with chloride and in theory still containing it's full load of Na

Edited September 15, 2009 by Arthur

[Mumbles]

Is is possible to get KCl from garden shops or the like? It's pretty commonly sold as a fertilizer in the US as Muriate of Potash, or even straight potash. I found the latter out the hard way as I was trying to get some K2CO3.

[Arthur]

Great clue Mumbles! I've just found it by the 25 kilo bag. Thanks

[50AE]

Well, I remember double recrystallizing and washing two times my KClO3 made from NaCl and my blue color comp was burning yellowish.

[Arthur]

While I'm fully aware that removing Na impurity is a right PITA, my understanding of the cell chemistry is that the K salts cannot be electrolysed to Perchlorate, (Only Chlorate).

 

Is anyone able to prove that K salts will oxidise to Perc? Having found Commercial KCl I'd much rather work with that, but so far web research has indicated that oxidation to perc requires the higher solubilities that the sodium salt gives. Has anyone any evidence to prove or refute this?

[FrankRizzo]

Arthur,

 

That is incorrect. Read this thread from the first page.

[Bonny]

and also read Swede's blog...he made some perc from his K-chlorate.

[Bonny]

Double posting... maybe this should be in the happiness thread!! I turned off the power to have a peek into my cell today and it's looking great!! Although it's hard to tell looking through water, there's at leaat an inch or 3 of chlorate crystals (can't be anything else) in the bottom of my bucket. Another week and I'll extract and wash 'em up!

[Swede]

Congrats! You will be impressed at the yield. The crystals are fat, easily separated and washed, and there will be more by mass than you'll suspect. Recharge the liquor with KCl and the next run will have a 30% or so head-start.

[Ventsi]

I decided to start some NaClO3 to swap with KCl whenever I get some.

So far I have two beautiful electrodes [swede] , 14A, 5V, 1.75 Liters of liquor in the cell. I have been running it almost 24 hours now and its going strong with very little salt creep.

 

My concerns are: Its pretty flipping hot, around 65 *C or so.

Then there are a couple large crystals covered by a film of fine crystals, both Na salts are supposed to be super soluble, so whats going on there??

 

Well I just re-hydrated it off with some more liquor.

 

 

Oh! The crystals might be the Na aluminosilicate used as a anti caking agent? But then there is a 1/4" layer on a 6x6 "floor" .

Edited September 25, 2009 by Ventsi

[Bonny]

I harvested my first batch of KClO3 today, and I'm very happy. The cell was a 17l bucket, MMO anode and Ti cathode, powered by a PC power supply delivering ~20A for 18 days. I'm not sure on the amount, but several kgs for sure. My goal is perchlorate, but this is a great start, and a lot of potential future feed stock. The KClO3 in the pic is after the first cold water wash, I think it needs another as I (think) I can still smell hypochlorite(?) on the crystals...maybe to many fumes in the garage. Anyway, here is a pic of the cell and the crop in a 4l pot.

[WSM]

I shared my cell lid "seal" with Swede and he suggested I share it with the group:

 

To "seal" the lid I've had reasonable success by gluing a strip of PVC cut from the same pipe with a section cut out to make a round ring that fits inside the pipe itself. I leave a gap large enough to just fit some aquarium silicone air tube between the PVC ring on the lid and the ID of the pipe, making a silicone seal between them. I use silicone sealer (GE Silicone I) to glue the silicone tubing to the PVC lid. With a tight fit it does a very reasonable job sealing the lid on and allows very little (if any) salt creep.

 

 

When I cut a section out of the short PVC ring, I use a heat gun to soften and form the ring (PVC is soft and pliable at about 275 F; handle with leather gloves and take care not to burn the PVC while heating) and cool it with a wet rag when it's right to get it rigid again. If you keep it flat on the mounting side it should be easy to glue together and onto the lid with PVC cement.

 

The flush ends of the aquarium air tube are glued together with a little silicone sealer after I join them with a short piece of the same air tube sliced along the length, rolled and stuffed into the ends to form the seal ring (Poor Man's O-ring). It's a somewhat messy process but it's effective and easy to replace later if it gets destroyed.

[Swede]

I decided to start some NaClO3 to swap with KCl whenever I get some.

So far I have two beautiful electrodes [swede] , 14A, 5V, 1.75 Liters of liquor in the cell. I have been running it almost 24 hours now and its going strong with very little salt creep.

 

My concerns are: Its pretty flipping hot, around 65 *C or so.

Then there are a couple large crystals covered by a film of fine crystals, both Na salts are supposed to be super soluble, so whats going on there??

 

Well I just re-hydrated it off with some more liquor.

 

 

Oh! The crystals might be the Na aluminosilicate used as a anti caking agent? But then there is a 1/4" layer on a 6x6 "floor" .

 

If starting with plain NaCl salt, there should be NO crystallization at all throughout the entire process of chloride to chlorate. What was the source of your salt? The 65 degrees C is a tad high but really not bad at all, and shouldn't cause grief. Is the entire cell at 65, or is it a localized heating near the electrodes? At 1.75 liters, I'm guessing the whole cell is at that temp. Really, 65 is nothing. Just watch out for the straps heating excessively and softening the plastic. A fan that blows ambient air over the cell does wonders, and will probably drop the cell 10 degrees or more. But higher temps actually increase the efficiency a bit.

 

I am concerned about the presence of crystals. Can you get a sample of them out of the cell? Try dissolving them in hot water. All I can think of is some odd contamination that caused a crystallization from some intermediate ionic species created during the electrolysis, but I really have no idea.

 

In the United States, a good NaCl is stuff in a blue bag called "Solar Salt" and sells for $5 for 40 pounds. It is nicely pure and dissolves with ease... I use it in my swimming pool.

 

@ Bonny: I saw the pictures and they look great - looks to be an excellent batch, and the amount looks appropriate for the size of the cell you used. On the hypochlorites - I have never smelled hypo after the xtals are washed and truly dried. I probably leave them spread out (shaded and gently covered with a cloth) for 3 to 4 days, even though they feel dry within a day. Opening a container of harvested xtals dried in this manner reveals no hint of bleachiness, so I don't know what the issue is. It is very tempting to skimp on the washing to avoid losing product. I don't know if you did this, but it is something to consider. For 2 to 4 kilograms of potassium chlorate, I'll use at least 2 to 3 liters of water at about 4 degrees C, save the wash water, recharge that with chloride, then add it to the next run. I also do a very brief and light final was with cold water and cold ethanol, maybe 75:25, for wetting. I can't support the idea of ethanol with any real scientific data - it does limit the amount of chlorate lost to the wash - but I've done it and I think it helps. Water with ethanol in it gets boiled to remove the ethanol, and for a 2 kg batch, the water + ethanol volume is maybe a liter, no more. The water, of course, gets recycled too.

 

@ WSM: I do like this idea, and it dovetails into the "cylindrical PVC tank" concept. The inner ring can be made from a sliced-off section of PVC fitting, and if it doesn't fit nicely it can be slotted and slightly bent and made smaller or larger. I'm also thinking the main tubular cell could be greased with vaseline, and the silicone gasket created and cured with the lid in place. This is a much better option than trying to cut a channel for viton o-ring stock, which is impossible without specialized tools.

 

The PVC ring will help protect the silicone from chlorine and other noxious gasses. Eventually it might die, but such a gasket is very easy to scrape and replace. And it will truly be gas tight.

 

Perhaps one of the specialized "form-a-gasket" silicones from an auto-parts store might have a bit more chemical resistance? I don't know, but the concept overall is excellent.