making potassium (per) chlorate

[WSM]

Pool chlorinating tablets are usually available. Pool chlorine test kits will measure the 0 - 10ppm range easily.

 

 

That's a good suggestion (for sanitizing or disinfection purposes, not chlorate cells).

 

WSM

[WSM]

Since I'm off work for a little while (I'm off sick with a bacterial infection, not Covid19, but I'm on antibiotics for 10 days), I'm going to work on the high temperature NaClO₃ cell, and see if I can get it ready for a trial run after the weather starts to cooperate (I like to run these cells outdoors).

 

I'm using a 5 liter, round bottom, borosilicate reaction vessel with a wide mouth, gasketed opening.

 

 

It's sitting in a heating mantle, but I don't plan to heat it externally, unless that becomes necessary (which I don't believe it will; with a proper design it should self-heat using slightly over-sized electrodes). I plan to fill it to 4 liters maximum, or at least 3.5 liters of sodium chloride solution, saturated at 25^oC. I have some spent electrolyte from a previous run of my larger sodium chlorate cell. I just need to add purified sodium chloride brine to replenish it for the high temperature test run.

 

The cell lid will be a 1" (~25 mm) thick plate of PTFE, which is impervious to the conditions of the cell. I need to find a method of securing the lid to the cell without stressing the glass reaction flask.

 

The plan is to run the cell at an average temperature of 110^oC, where the excess water will boil off, naturally concentrating the electrolyte, and allowing the sodium chlorate to drop out of solution when the electrolyte drops to room temperature (rather than chilling it). After harvesting the chlorate, the "spent" electrolyte will be recharged with chloride by adding brine and running again.

 

The idea is from a patent that Arthur shared with me a few years ago.

 

After running a somewhat large sodium chlorate cell (~22 Liter capacity, PVC tank), for 6 weeks at roughly 40^oC before shutting it down, and then harvesting roughly 5 Kg of NaClO₃ crystals, I felt there has to be a better (faster and less complicated) way.

 

As I researched the patent, and the more I learned about the process; the more convinced I became of the value of giving it a try. By my thinking, it should expedite the sodium chlorate production enough to make a large enough stockpile to feed my perchlorate production tests for a long time. I certainly hope so and we'll see...

 

WSM

Edited April 12, 2020 by WSM

[Andead]

I have sodium chlorate crystals precipitating out on the surface and sides of my 5L container. Should i now switch my mmo cathode into the lead dioxide anode to begin conversion of chlorate to perchlorate?

[WSM]

I have sodium chlorate crystals precipitating out on the surface and sides of my 5L container. Should i now switch my mmo cathode into the lead dioxide anode to begin conversion of chlorate to perchlorate?

 

To keep things separate (and to preserve your anode), you may want to collect the sodium chlorate crystals and make your perchlorate electrolyte from only them. The sodium chlorate cell liquids may still contain high amounts of sodium chloride, which is a real problem for platinum anodes, but might also be hard on a lead dioxide anode (I'm not sure).

 

I ran my perchlorate experiments using lab grade sodium chlorate (till it ran out). Next my focus has turned to making sodium chlorate. My plan is to produce enough (high purity sodium chlorate) that I can run all my other perchlorate experiments with the same large batch of sodium chlorate (not mix batches) to eliminate the question of which batch of chlorate worked best.

 

I feel that starting with crystalline sodium chlorate eliminates adding unwanted contaminants to the perchlorate process (from residues left in the sodium chlorate electrolyte).

 

I think some patience and extra steps will pay off in this case.

 

Congratulations on harvesting sodium chlorate crystals.

 

WSM

Edited April 17, 2020 by WSM

[Andead]

Thanks WSM once im done from my homework i will begin processing

[WSM]

Thanks WSM once im done from my homework i will begin processing

 

 

Excellent! Let us know how it goes.

 

WSM

[WSM]

I'm beginning to get the setup for the high temperature sodium chlorate cell experiment assembled.

 

The 5 liter borosilicate reaction flask has a large gasketed opening, where I plan to set a Viton seal and a thick PTFE lid. The lid will be prepared with tapped holes to accommodate PVDF fittings for the electrodes, vent tube and various accessories required for running and monitoring the cell parameters.

 

I believe pH control will be vital to maintaining a healthy environment for the cell structure, since (if I remember correctly) the borosilicate glass vessel tolerates a pH range of 3-10, and an uncontrolled chlorate cell can readily exceed the safe alkalinity level and begin to break down the cell container. The temperature I plan to run the cell at (110^oC) will only exacerbate the problem, so pH control is mandatory and not optional.

 

There is a lot of preparation to be done before I start the cell, and I'm only at the beginning stages of getting it ready. I'll post photos and update the list as things progress.

 

WSM

Edited July 12, 2020 by WSM

[sefrez]

 

To keep things separate (and to preserve your anode), you may want to collect the sodium chlorate crystals and make your perchlorate electrolyte from only them. The sodium chlorate cell liquids may still contain high amounts of sodium chloride, which is a real problem for platinum anodes, but might also be hard on a lead dioxide anode (I'm not sure).

 

I ran my perchlorate experiments using lab grade sodium chlorate (till it ran out). Next my focus has turned to making sodium chlorate. My plan is to produce enough (high purity sodium chlorate) that I can run all my other perchlorate experiments with the same large batch of sodium chlorate (not mix batches) to eliminate the question of which batch of chlorate worked best.

 

I feel that starting with crystalline sodium chlorate eliminates adding unwanted contaminants to the perchlorate process (from residues left in the sodium chlorate electrolyte).

 

I think some patience and extra steps will pay off in this case.

 

Congratulations on harvesting sodium chlorate crystals.

 

WSM

 

First post on amateurpyro.

 

I've been making chlorates and perchlorates for a few months on small scale using a platinized titanium anode and two titanium electrodes on either side. I have about 22 days cumulated run time on it. The anode has seemed to hold up well (appears no different than when I first started using it.) I know that may not imply "no corrosion." But voltage / current relationships have remained the same which suggests there hasn't been any titanium passivation and therefore suggests no pin hole formations in the platinum coating. The cathodes actually seem to be the ones that suffer, although very minor. Hydrogen embrittlement?

 

You say chloride is a problem with platinum. Do you mean in general, or when making perchlorates? If it is the latter, I need to see the distinction between the two which is clearly not made simply by the presence of chloride. Is it the low "but not negligible" chloride levels in a perchlorate process? An interaction between chloride / perchlorate and the anode?

 

Thanks.

Edited July 17, 2020 by sefrez

[Arthur]

Using a platinum electrode is a good way to progress directly from chloride to perchlorate, BUT, the platinum electrode is damaged when there is a low concentration of chloride ions in solution. Hence all known commercial processes use a two part process, first to make and purify chlorate using non precious metals, second using platinum or clad electrodes to turn good chlorate into good perchlorate. The aim (after making perc) is to minimise platinum losses.

[sefrez]

Thanks for the reply. Here is my annoyingly long reply.

 

So low chloride levels leads to more corrosion, regardless. Making perchlorate from chlorate is going to be a harsher process for a platinum electrode because chloride levels are low. To save platinum however, electrodes like MMO are used for chlorates because they work for that. Is that what you are saying?

 

Or are you saying that its possible to get perchlorates while maintaining sufficient chloride? I was thinking the current efficiency for perchlorates is low when chloride is present. I have actually had a gradual increase in perchlorates in my "chlorate" cell over time and have had to separate that out. So evidently that does happen to some extent, just not effectively. OR, are you making the distinction between "low" chloride levels and "no" chloride. I.e. pure chlorate to perchlorate = fine, chlorate contaminated with chloride = not fine. To me there is no such thing as "no" chloride, but perhaps some low threshold that is practically "no" chloride.

 

My process has been this:

Make sodium chlorate from sodium chloride using the platinum electrode never (intentionally) letting the chloride levels drop below ~ 10g/100mL. The current density has been around 150mA / cm^2, and cell temperature ranging from 48-55C.

This process is continued until chlorate begins to crystalize out upon which I let the solution cool to room temperature for more crystal mass to form.

These (usually large dime to quarter sized) crystals are separated and dried for later purification, conversion to KClO3, or conversion to NaClO4.

The cell solution is recycled back into the cell with chloride levels replenished and everything repeated.

 

When going to perchlorate, I would take the NaClO3 crystals and setup a saturated solution. This would be electrolyzed to form perchlorate. I would approximate the conversion efficiency by looking at how much perchlorate had formed for a given charge put through the cell. I did this by the annoying process of taking a sample, drying it to form a salt mass, grinding it in a mortar, and using acetone as a solvent for the perchlorate to separate it out. This could then be weighed. Anhydrous sodium perchlorate is about as difficult to deal with as anhydrous sodium hydroxide with respect to being deliquescent.

 

After I was satisfied with the conversion, I destroyed the remaining chlorate by boiling the solution adding HCl until an indigo carmine test came up negative for chlorate.

 

 

I feel like my process could definitely be improved, but it has seemed to be working. Though I may be unaware of a high anode corrosion rate.

Edited July 17, 2020 by sefrez

[Jimjimboom]

Then your not going to be successful. (I was never talking about buying anything off ebay, i was talking about buying KClO4.) Electrolytic cells are like salt water fish tanks... They require a hell of alot of precise adjustments and being off can kill the fish (rate of formation/forming anything at all).

 

Hypochlorite decomposition through heat and subsequent metal ion juggling result in a sodium infested product and its alot of work for very little payoff.

 

Cl2 absorption into hot caustic (-OH) solutions is extremely slow and dangerous with the Cl2 gas.

 

If you have a nice platinum anode laying around or are going to actually invest enough time to decide which kind of anode fits your situation best... And find one or make one, then you should be able to set up a cell with minimal effort. However, its going to fail at some point and thats really your responsibility to deal with.

 

The info is out there. Learn more.

We don't want to have to spoon feed you at every step.

 

(I'm not replying to this thread again.)

[Jimjimboom]

This guy isnt kidding if you cant buy it and dont know what you are doing, dont bother! It is a big risk for someone who doesnt know what they are doing! If you live in australia and cant get it, send me a private message! If your somewhere else, just dont bother! You will end up dead! If you dont know the chemistry or are unsure! Just stay alive!

This guy isnt kidding if you cant buy it and dont know what you are doing, dont bother! It is a big risk for someone who doesnt know what they are doing! If you live in australia and cant get it, send me a private message! If your somewhere else, just dont bother! You will end up dead! If you dont know the chemistry or are unsure! Just stay alive!

[sefrez]

I don't know if you are replying to me, but I hardly consider a few questions about electrode corrosion me not knowing what I am doing. I have done quite a bit of research on chlorates. Not as much on perchlorates I admit. But I am familiar with the two stage process of separating out the othe ions (chlorides, hypochlorites) before perchlorates. I'm just trying to get clarification on seemingly contradictory statements (which I believe is based in semantics.)

 

Again, I don't know if you are replying to me, but if so I don't appreciate being told I don't know what I am doing. Of course I could know more, but those things are based around efficiency, hardly indicative of me being unsafe.

 

But on the off chance I really don't know what I'm doing, I assume let natural selection take its course given I feel I know enough...

[Arthur]

The chlor-alkali process is well known science and engineering and used daily on huge industrial scale for the manufacture of "chloros bleach" by the million gallons and for producing lots of other compounds as either products or ingredients of further processes.

 

The chemistry that makes chlorate production easy is the solubility change with temperature of sodium chlorate and sodium chloride. Sodium chloride solubility is largely constant over 0 - 100C. Sodium chlorate solubility increases with temperature. SO a hot solution of mixed chloride and chlorate will cool and precipitate only the chlorate. From this reasonably clean chlorate it's easy to electrolyse against a platinum electrode to make perchlorate -with no chloride to mess with the platinum.

Reference- https://en.wikipedia.org/wiki/Solubility_table and scroll down to sub table S (for sodium!)

 

Industrial perc production relies on this and crystalises some of the chlorate out of the brine and passes the chlorate to platinum electrode cells returning the depleted brine to be re loaded with salt and re used..

IN professional use chlorate cells are run hot 1/because chlorate doesn't form in cold reactions and 2/ because the surplus water just evaporates and 3/ because a hot solution will ppt out more chlorate on each cycle.

[sefrez]

The chlor-alkali process is well known science and engineering and used daily on huge industrial scale for the manufacture of "chloros bleach" by the million gallons and for producing lots of other compounds as either products or ingredients of further processes.

 

The chemistry that makes chlorate production easy is the solubility change with temperature of sodium chlorate and sodium chloride. Sodium chloride solubility is largely constant over 0 - 100C. Sodium chlorate solubility increases with temperature. SO a hot solution of mixed chloride and chlorate will cool and precipitate only the chlorate. From this reasonably clean chlorate it's easy to electrolyse against a platinum electrode to make perchlorate -with no chloride to mess with the platinum.

Reference- https://en.wikipedia.org/wiki/Solubility_table and scroll down to sub table S (for sodium!)

 

Industrial perc production relies on this and crystalises some of the chlorate out of the brine and passes the chlorate to platinum electrode cells returning the depleted brine to be re loaded with salt and re used..

IN professional use chlorate cells are run hot 1/because chlorate doesn't form in cold reactions and 2/ because the surplus water just evaporates and 3/ because a hot solution will ppt out more chlorate on each cycle.

 

This is nearly precisely the process I have been using and am aware of everything you say but the chloride bit with respect to chlorate production and perchlorate production. In my research I have read about platinum working well for making chlorates when chloride levels are maintained above some value (obviously an exact value would depend on many factors, but generally it is the case that more chloride -> less corrosion.)

 

But then I see statements regarding making perchlorate and platinum corrosion whereby it is said pure chlorate should be used (no chloride) to limit corrosion. This appears contradictory. What I am trying to figure is what makes these two processes different that remedies these seemingly contradictory statements. Or is it I have at least one statement wrong?

 

Again, thank you for giving me information as apposed to just telling me to take up a different hobby without knowing much about me.

[Mumbles]

I think Jimjimboom was replying to that 13 year old thread he quoted above his post. For you know.....reasons.

[markx]

 

This is nearly precisely the process I have been using and am aware of everything you say but the chloride bit with respect to chlorate production and perchlorate production. In my research I have read about platinum working well for making chlorates when chloride levels are maintained above some value (obviously an exact value would depend on many factors, but generally it is the case that more chloride -> less corrosion.)

 

But then I see statements regarding making perchlorate and platinum corrosion whereby it is said pure chlorate should be used (no chloride) to limit corrosion. This appears contradictory. What I am trying to figure is what makes these two processes different that remedies these seemingly contradictory statements. Or is it I have at least one statement wrong?

 

Again, thank you for giving me information as apposed to just telling me to take up a different hobby without knowing much about me.

 

The topic of chloride content in a Pt anode perchlorate cell is actually quite contradictory to be honest. At least it is for me. The popular "lore" surrounding the topic seems to suggest a zero tolerance towards initial chloride content in the starting electolyte as a must.....but the electrochemical processes in the system shall tend to give rise to an equilibrium chloride content in the cell even if the initial chlorate stock is free of it.

I've experimented quite a bit with this process and Pt plated anodes. My experience so far suggests that initial chloride content is not the main threat to anode life, but the end stages of perchlorate conversion seem to act the harshest upon the remaining life span of a Pt plated anode setup.

In any practical way it makes sense to look at a Pt plated anode as a consumable item in the process. One or other way it is going to finally give up the ghost, but in my experience high applied voltage across the cell (in excess of 5V) and striving towards a full conversion are two of the most critical parameters that seem to promote the degradation.

[Arthur]

The tech paper I read said that platinum consumption (loss) could be kept below 10 grammes per tonne, 10 g is a lot more than the Pt on a plated electrode and this was a best professional conditions. Poorly smoothed DC current is also a cause of platinum erosion, ripple on the supply line is a killer of electrodes. Motor-generator sets producing six phase low volts AC was rectified to even lower ripple than could be found off normal mains three phase.

[WSM]

Using a platinum electrode is a good way to progress directly from chloride to perchlorate, BUT, the platinum electrode is damaged when there is a low concentration of chloride ions in solution. Hence all known commercial processes use a two part process, first to make and purify chlorate using non precious metals, second using platinum or clad electrodes to turn good chlorate into good perchlorate. The aim (after making perc) is to minimise platinum losses.

 

 

It was my understanding that high chlorides was a problem for platinum anodes (low chlorides preferred), when converting chlorate to perchlorate.

 

WSM

Edited July 19, 2020 by WSM

[WSM]

Thanks for the reply. Here is my annoyingly long reply.

So low chloride levels leads to more corrosion, regardless. Making perchlorate from chlorate is going to be a harsher process for a platinum electrode because chloride levels are low. To save platinum however, electrodes like MMO are used for chlorates because they work for that. Is that what you are saying?

Or are you saying that its possible to get perchlorates while maintaining sufficient chloride? I was thinking the current efficiency for perchlorates is low when chloride is present. I have actually had a gradual increase in perchlorates in my "chlorate" cell over time and have had to separate that out. So evidently that does happen to some extent, just not effectively. OR, are you making the distinction between "low" chloride levels and "no" chloride. I.e. pure chlorate to perchlorate = fine, chlorate contaminated with chloride = not fine. To me there is no such thing as "no" chloride, but perhaps some low threshold that is practically "no" chloride.

My process has been this:

Make sodium chlorate from sodium chloride using the platinum electrode never (intentionally) letting the chloride levels drop below ~ 10g/100mL. The current density has been around 150mA / cm^2, and cell temperature ranging from 48-55C.

This process is continued until chlorate begins to crystalize out upon which I let the solution cool to room temperature for more crystal mass to form.

These (usually large dime to quarter sized) crystals are separated and dried for later purification, conversion to KClO3, or conversion to NaClO4.

The cell solution is recycled back into the cell with chloride levels replenished and everything repeated.

When going to perchlorate, I would take the NaClO3 crystals and setup a saturated solution. This would be electrolyzed to form perchlorate. I would approximate the conversion efficiency by looking at how much perchlorate had formed for a given charge put through the cell. I did this by the annoying process of taking a sample, drying it to form a salt mass, grinding it in a mortar, and using acetone as a solvent for the perchlorate to separate it out. This could then be weighed. Anhydrous sodium perchlorate is about as difficult to deal with as anhydrous sodium hydroxide with respect to being deliquescent.

After I was satisfied with the conversion, I destroyed the remaining chlorate by boiling the solution adding HCl until an indigo carmine test came up negative for chlorate.

I feel like my process could definitely be improved, but it has seemed to be working. Though I may be unaware of a high anode corrosion rate.

 

 

I made sodium perchlorate from sodium chlorate using a platinum on titanium anode. No (or very low) chloride levels and the anode performed very well with no perceptible deterioration.

 

WSM

[WSM]

The chlor-alkali process is well known science and engineering and used daily on huge industrial scale for the manufacture of "chloros bleach" by the million gallons and for producing lots of other compounds as either products or ingredients of further processes.

The chemistry that makes chlorate production easy is the solubility change with temperature of sodium chlorate and sodium chloride. Sodium chloride solubility is largely constant over 0 - 100C. Sodium chlorate solubility increases with temperature. SO a hot solution of mixed chloride and chlorate will cool and precipitate only the chlorate. From this reasonably clean chlorate it's easy to electrolyse against a platinum electrode to make perchlorate -with no chloride to mess with the platinum.

Reference- https://en.wikipedia.org/wiki/Solubility_table and scroll down to sub table S (for sodium!)

Industrial perc production relies on this and crystalises some of the chlorate out of the brine and passes the chlorate to platinum electrode cells returning the depleted brine to be re loaded with salt and re used..

IN professional use chlorate cells are run hot 1/because chlorate doesn't form in cold reactions and 2/ because the surplus water just evaporates and 3/ because a hot solution will ppt out more chlorate on each cycle.

 

True!

 

WSM

[WSM]

The topic of chloride content in a Pt anode perchlorate cell is actually quite contradictory to be honest. At least it is for me. The popular "lore" surrounding the topic seems to suggest a zero tolerance towards initial chloride content in the starting electolyte as a must.....but the electrochemical processes in the system shall tend to give rise to an equilibrium chloride content in the cell even if the initial chlorate stock is free of it.

I've experimented quite a bit with this process and Pt plated anodes. My experience so far suggests that initial chloride content is not the main threat to anode life, but the end stages of perchlorate conversion seem to act the harshest upon the remaining life span of a Pt plated anode setup.

In any practical way it makes sense to look at a Pt plated anode as a consumable item in the process. One or other way it is going to finally give up the ghost, but in my experience high applied voltage across the cell (in excess of 5V) and striving towards a full conversion are two of the most critical parameters that seem to promote the degradation.

 

 

Understanding these details lead to my success in making sodium perchlorate from sodium chlorate.

 

I ran my cell using light current loading (~0.15 A/cm²) and about 4.2 Vdc. It ran slower but the electrodes suffered no perceptible damage.

 

WSM

Edited July 22, 2020 by WSM

[WSM]

The tech paper I read said that platinum consumption (loss) could be kept below 10 grammes per tonne, 10 g is a lot more than the Pt on a plated electrode and this was a best professional conditions. Poorly smoothed DC current is also a cause of platinum erosion, ripple on the supply line is a killer of electrodes. Motor-generator sets producing six phase low volts AC was rectified to even lower ripple than could be found off normal mains three phase.

 

 

True. If you need to build a power supply, I strongly advise a good filter scheme to clean up stray ripple (AC elements in the DC current). A Pi filter is usually used to great effect (look it up in your favorite search engine).

 

I've purchased a couple power supplies that supply good, clean DC output.

 

WSM

[sefrez]

 

The topic of chloride content in a Pt anode perchlorate cell is actually quite contradictory to be honest. At least it is for me. The popular "lore" surrounding the topic seems to suggest a zero tolerance towards initial chloride content in the starting electolyte as a must.....but the electrochemical processes in the system shall tend to give rise to an equilibrium chloride content in the cell even if the initial chlorate stock is free of it.

I've experimented quite a bit with this process and Pt plated anodes. My experience so far suggests that initial chloride content is not the main threat to anode life, but the end stages of perchlorate conversion seem to act the harshest upon the remaining life span of a Pt plated anode setup.

In any practical way it makes sense to look at a Pt plated anode as a consumable item in the process. One or other way it is going to finally give up the ghost, but in my experience high applied voltage across the cell (in excess of 5V) and striving towards a full conversion are two of the most critical parameters that seem to promote the degradation.

 

We seem to be on the same spectrum of thought.

 

I do believe as well that the low perchlorate (and chloride) levels cause more corrosion. I actually smell what I believe to be ozone near the end of conversion. Creating that species at a higher level in the end (going by the fact I can't smell it in the beginning) may be part of the reason. It reminded me of electrolyzing sulfuric acid. Some ozone is produced there too.

 

The tech paper I read said that platinum consumption (loss) could be kept below 10 grammes per tonne, 10 g is a lot more than the Pt on a plated electrode and this was a best professional conditions. Poorly smoothed DC current is also a cause of platinum erosion, ripple on the supply line is a killer of electrodes. Motor-generator sets producing six phase low volts AC was rectified to even lower ripple than could be found off normal mains three phase.

 

Well, back a few years ago I was into flying RC helicopters. Not the little stuff (not the big stuff either,) but having a rotor/blade span of 1 meter. These helicopters run off of pretty high capacity with high current charge / discharges. So I invested in an "iCharger Duo". Its basically a sophisticated charging station that covers various battery types, including lithium polymer (the type used in RC heli's these days.) It can charge at up to 30A, records time, charge transfer, regulates current, voltage, etc. I've kind of rigged it up where I can "charge" my chlorate cell. So I have high current capabilities and details making the process easier to keep track of. I haven't looked at the output voltage of it with an oscilloscope yet. Maybe I should. In the event its not satisfactory, I wonder if I can put a smoother in between.

 

 

 

It was my understanding that high chlorides was a problem for platinum anodes (low chlorides preferred), when converting chlorate to perchlorate.

 

WSM

 

Indeed. Just contradicts what is said about chlorides in chlorate cells, at least on the surface. Maybe a distinction in the processes can be made where the contradiction is remedied.

 

 

 

I made sodium perchlorate from sodium chlorate using a platinum on titanium anode. No (or very low) chloride levels and the anode performed very well with no perceptible deterioration.

 

WSM

 

About how far have you taken the conversion? Say chlorate conversion proportion by mass or moles?

 

 

 

Understanding these details lead to my success in making sodium perchlorate from sodium chlorate.

 

I ran my cell using light current loading (~1.5 A/cm²) and about 4.2 Vdc. It ran slower but the electrodes suffered no perceptible damage.

 

WSM

 

Do you mean 0.15 A/cm^2? 1.5 A/cm^2 seems large! I've been running at about 0.15A/cm^2 myself.

 

 

Anyway, if full conversion to perchlorate is the main issue (meaning low chlorates and low chlorides,) perhaps a method to take off perchlorates somewhere before this is an issue should be done and that which remains recycled with chlorates replenished. Really, exactly the same process for chlorates, but instead of keeping chloride present to some threshold, its chlorates. One obvious way to do it is how I have already mentioned, remove water drying the salts, crushing well, and using acetone as a solvent for NaClO4 (of which both chlorate and chloride are hardly soluble.) But if you do this once you will never want to do it again. If you've tried removing H2O from NaClO4 to form the anhydrous NaClO4, you will understand this. The only two things it has over NaOH is that it wont eat your tissues or your glassware.

 

Another, easier way, would be crystallization. If enough chlorate can be converted, concentrating the solution could cause NaClO4 (monohydrate?) to crystalize out and you could pour of the solution for recycling. The crystals could then be processed further to what ever end. They would need to be stored in a impervious bottle as if air with moisture is able to get to it, it will turn into a puddle. No drying on a coffee filter is an option without serious perchlorate losses...

 

If potassium perchlorate is the end goal, I think the easiest way would be to selectively precipitate that by its low solubility. I think that could be done without pulling chlorate out as well if you deal in right amounts. Again, remaining solution would be reused by adding more pure NaClO3.

[markx]

Solved the issue for myself with regenerable DIY Pt plated anodes. Let it run quietly until it is as good as it gets and farewell to the anode after about 2-3 full conversions. Regenerate the anode (make a new one) and repeat if neccessary. All the other options like selective recristallisation or selective solvent separation are just an unreasonable amount of work that I have no inclination to engage in