Long running Potassium Chlorate may Perc cell

[Psymon89]

Last year i had build several "Reactor Head´s", to go from Chloride to Chlorate. Ive done everything only with OTC products, Ebay etc.

In the end i was Running a 8L 4Kg Chlorate cell on 200x60 MMO anode at 4.x Volts an around 35 to 42 Amps, cuz im not very good in Math i wasnt Calculating how long i have to run but i decided after 10 Days it was enough, i ended up with around 3 kg of chlorate wich precipitated out of solution in form of beautiful shiny crystals.

Im gonna show some Pics.

 

But now i want to Build one for Perchlorate with automatic refeeder function, to replenisch the KCLO3 while KCLO4 is precipitating.

Do you think the refeed function will be working? something like a teasieve inside the Reactor Head filled with KCLO3 which will dissolve if the concentration in the sole sinks.

I always use a Glass Vase as cell, last was D150mmx500mm and now for the Perc it will be 200x300, aswell around 8 Liters.

Used a Glass Plate on top, Drilled with cheap Glassdrills from Euroshop, but Later changed to a PET Plate.

Use PTFE tubing 4x6 as Gas exhaust to the aquarium bubbler and shield the Meat-Oventhermocouple

Titanium Spacers are a Bicycle Part for the rear damper, available with 25-52mm length.

Changed the Cables from 4mm2 to 10 mm2 because i was running at 35-42A @ 4,6V

 

 

Edited March 27 by Psymon89

[mx5kevin]

The conversion of KClO3 to KClO4 is too slow process. It will not work with a PbO2 anode because KClO4 will precipitate on the anode and crystals will be deposited on it. It works with a thick platinum anode coated on a silver base, but the process produces a very small amount of KClO4 occasionally. The other problem is that as the KClO4 precipitates, the process slows down. It will take many times longer to produce the same amount of KClO4 from KClO3 electrolysis compared to NaClO4. Using NaClO4, large quantities can be produced on occasion. There are two tricks here: If someone finds the NaCl to NaClO4 conversion too slow, they use KClO3 for the double displacement reaction. Because there are cases where KClO3 is produced much faster than NaClO3. Anyone who doesn't have this problem uses KCl for the double displacement reaction. The NaCl are reused in the chlorate cell if KCl are used. The NaClO3 are reused in the perchlorate cell if KClO3 are used.

Edited March 27 by mx5kevin

[mx5kevin]

You can dissolve 73g KClO3 in a 1000ml room temperature cell. Some of this will precipitate in the form of KClO4. When a certain amount of KClO4 precipitates, the process slows down drastically. Ideally, you should filter it every two days and then dissolve fresh KClO3.
You can dissolve 357g NaCl in a 1000ml room temperature cell to convert it ~750g NaClO4.
In the first method, as the KClO4 precipitates and filtered, fresh KClO3 must be dissolved in the solution at high temperature than cool it down. And you have to repeat this at least ~15X to get to what you once extracted with the NaClO4 method. I tried the KClO3->KClO4 conversion method in pure water using electrolysis a long time ago, but I realized it was uneconomical. Anodes especially platinum used for perchlorates are severely damaged if operated above 45°C (degrees Celsius) at long term. This is precisely why hot solutions cannot be used for electrolysis in perchlorate production.

Edited March 27 by mx5kevin

[Psymon89]

i just got a thing in my brain, what happens if i put fluoridic acid some drop innit? does KF helps something against chcloric acid?

 

im just back from holiday, and i found in a chinese shop in PT, a bottle of 2% HF acid and brang it with the hand luggage

 

i post a picture what will be a topfeeder for KCLO3 when the 4th is falling out to bottom and some of my actual changeable head project

Edited April 4 by Psymon89

[AustralianPyromaniac]

The cell is beautiful and well-engineered but the principals are flawed! 

KClO₃ can hardly be turned into KClO₄ directly, as Kevin has said.

The reaction you are trying to perform is given by (1). This is the anodic oxidation of the ClO₃^– ion. The competing reaction is the oxidation of water given by (2). The potential of these two reactions is very close (1.19V vs. 1.23V), and both reactions compete strongly. To favor (1) over (2), we must optimise the conditions of the cell.

(1) ClO₃⁻ + H₂O −2 e⁻ → ClO₄^– + 2H⁺ [1.19 V]

(2) H₂O + e^– → ½ O₂ + 2 H⁺ + 2 e^– [1.23 V]

Reaction (1) is favored when temperature is ‘low’ (45°C-50°C MAX), ClO₃^– concentration is ‘high’ (≥40g/100 ml) and current density is ‘high’ (≥300 mA/cm²) Further, we must select an electrode for which the overpotential for the ClO₄^– discharge is low.

KClO₃ is poorly soluble in water, to dissolve 40g/ 100 ml requires 85°C. If the temperature limit is respected instead, only 18g/ 100ml dissolves at 50°C. If we attempt to pass a large current density through a poorly conductive electrolyte such as this, enormous heat is generated which can boil the electrolyte without external cooling. It cannot work like NaClO₃ does.

Electrode selection is a further issue complicated by residual chloride levels in a single KClO₃ run, but even if we ignore this, the basic principle does not work.

The result of a cell charged with KClO₃ run past completion is simply the production of H₂ and O₂ and little KClO₄. The anode also dissolves quickly.

---

Fluoride ions improve current efficiency but cannot be used when the anode has titanium or platinum-coated titanium, only pure platinum can be used. Small amounts of fluorine gas are made that eat the titanium.

[Arthur]

Work with the sodium salt, the solubility controls everything. NaCl to NaClO3 then with different electrodes in a different cell NaClO3 to NaClO4 then in another chamber NaClO4 to KClO4 leaving NaCl solution ready to restart the process. Industrially platinum electrodes of several square feet are sandwiched between Titanium sheets and run at thousands of amps (just because the cell is the size of a hot tub!!!!)

[Psymon89]

you mean its possible to run from NaCl to NaClO4 with this cell?? or should i run the mmo to ClO3 first then change to the reactor head, like on the current pictures, i also changed the 5 electrode holder to MMO TI MMO TI MMO.

 

[mx5kevin]

15 hours ago, Psymon89 said:

you mean its possible to run from NaCl to NaClO4 with this cell?? or should i run the mmo to ClO3 first then change to the reactor head, like on the current pictures, i also changed the 5 electrode holder to MMO TI MMO TI MMO.

 

Using powdered sugar and methylene blue, you can calculate when perchlorate begins to appear. At this point, the MMO anode must be replaced with an anode suitable for producing perchlorate, otherwise it will be damaged! A PbO2 anode should not be used in a chlorate cell because its lifespan would be too short. The lifespan of the PbO2 anode in a perchlorate cell will still be less than half that of the MMO anode. In your case, it would be worth buying 2 PbO2 anodes, leaving one as a spare. And using the KCl+NaClO4 double displacement reaction to get KClO4, and reusing the NaCl to the chlorate cell. This cell is too big for a 50-200 micron thick platinum anode on a minimum 3mm thick niobium-copper or silver base. Platinized titanium anodes with 5 micron platinum layer are unusable thin and deteriorate very quickly. Therefore, the latter is out of the question.

You can't produce perchlorate with MMO anodes, no matter what type they are, none of them are suitable for it. Anyone who tries this will quickly destroy the electrode. However, this anode still tolerates the initial stage when perchlorate begins to form and can be detected with methylene blue.

PbO2 anode is very sensitive to pH, the cell should not be too alkaline, but not too acidic either. A pH of around 7 is an ideal range. It can be tested with a digital pH meter, but this must be rinsed very thoroughly with alkaline water and then plain water. The pH test strips are questionable, these usually all get bleached immediately. MMO anodes are not sensitive to a more alkaline solution, but PbO2 are. I haven't been able to test something like this with a pH test strip yet. I tried diluting and boiling the solution in a test tube, but none of that worked. This is very important for extending the life of the PbO2 anode.

Edited April 6 by mx5kevin

[Psymon89]

So i realized to go with NaCl first, so i Started my Cell today. i feed her 7,75L of 50°C saturated NaCl solution and powered up at 3.9V and 41.6A ConstantCurrent.

the Calculator says at 54% i takes aroun 2.33 weeks to chlorate, and 3.11 to Perchlorate, is this maybe right?

[mx5kevin]

33 minutes ago, Psymon89 said:

So i realized to go with NaCl first, so i Started my Cell today. i feed her 7,75L of 50°C saturated NaCl solution and powered up at 3.9V and 41.6A ConstantCurrent.

the Calculator says at 54% i takes aroun 2.33 weeks to chlorate, and 3.11 to Perchlorate, is this maybe right?

It's impossible to say, but it's realistic as a parameter. You will need 6-7V to make perchlorate. At the beginning, 3V is a good start, but this should be increased slowly later. Perchlorate can be made in half the time. By adhering to the parameters, the production time will always be almost the same. If the cell is not pH controlled, the process will be significantly slower. And you also need to replace the electrode when the chlorate is completely finished. The parameters are good. As the process progresses, the amperage drops and the process becomes slower and slower. There is a cheap test for perchlorate, the melting test. If it doesn't melt, the NaClO4 is ready. The melting points of NaClO3 and NaClO4 differ significantly. On a smooth conventional gas stove, using a ceramic crucible NaClO4 will not melt.

[Psymon89]

i think if i use less electrodes, the voltage will go up a bit.

if you say i need 6-7V to make perc, this voltage may be the reason why your electrodes will become destroyed as you say.

i always tried to be below 5.5-5.8V, but i never tested it for perc cuz for chlorate it works below.

Edited April 9 by Psymon89

[AustralianPyromaniac]

54% is optimistic. That is based on a high-temperature cell without pH control, but not letting pH get too high, so adjusting every 1-2 days. And current density has to be high on the cathode to prevent back reduction. It can be as low as 40%, but 45-50% is probably typical. 

I am looking at your cell, how do you get into it to add water? You will need to do a top-up once every 2 days at least, if not more often. Do you have to take all those nuts off? 

5-6.5V is typical for perchlorate. 

[mx5kevin]

16 hours ago, Psymon89 said:

i think if i use less electrodes, the voltage will go up a bit.

if you say i need 6-7V to make perc, this voltage may be the reason why your electrodes will become destroyed as you say.

i always tried to be below 5.5-5.8V, but i never tested it for perc cuz for chlorate it works below.

You will need later 6-7V because by the time the chlorate is ready, production will slow down drastically. As the process progresses, fewer and fewer amperes actually pass through the cell. This will fall below half of what it was when the solution was fresh, and this is natural. This won't harm the electrodes if the cell isn't overheated. This is gradually increased, and what also helps with this is pH regulation. I see you have an MMO and a lead dioxide anode. This is a perfect combination. The lead dioxide will wear out first no matter how you protect it. Don't use fewer electrodes, it will be much worse. In case of a positive methylene blue test, the MMO anode must be replaced with PbO2. The MMO anode also wears out over time, but its lifespan is twice that of PbO2. This is also the case in industrial settings, but the process is faster in home settings. This is expected to occur after approximately half a year of runtime in the case of PbO2. The large surface area electrodes and the adjustable power supply are a perfect combination. A little sodium persulfate 2g/l would still be recommended. What is missing is a slow, drop-by-drop pH control. If it is turned on every two days for an hour, for example, that is enough. This should only be added to the bottom of the solution and in small slow drops using a simple Plant Life Support Drip from flow 5-250ml/h.

[Psymon89]

i can unscrew the telfon screw on top,  to refill with a small glass funnel trough a 5.2mm hole.

there is some salt caking on the electrodes, i hope it grows around instead of pulling the plates to short circuit. how the salt will behave?

Ph regulation will be my next thing to invent, do you know which type of electrode will work for ph measure in this enviroment?

should i work with or without stirring? cuz the gas is dispersed with and without it just bubbles out from top and never reach the electrolyte below.

measured on the Outside wall, it has 50°C so i think inside will be around 65-75°C, i have to measure inside somehow, but the hole is 5.2 the thermoprobe has 6mm with the teflon coating and the proposed platinum plated probe didnt worked, maybe there are cracks or the platinum was too thin, i will recoat it one day, but i need to figure out which additive make the electrolyte coating thicker..

Edited April 12 by Psymon89

[mx5kevin]

3 hours ago, Psymon89 said:

i can unscrew the telfon screw on top,  to refill with a small glass funnel trough a 5.2mm hole.

there is some salt caking on the electrodes, i hope it grows around instead of pulling the plates to short circuit. how the salt will behave?

Ph regulation will be my next thing to invent, do you know which type of electrode will work for ph measure in this enviroment?

should i work with or without stirring? cuz the gas is dispersed with and without it just bubbles out from top and never reach the electrolyte below.

measured on the Outside wall, it has 50°C so i think inside will be around 65-75°C, i have to measure inside somehow, but the hole is 5.2 the thermoprobe has 6mm with the teflon coating and the proposed platinum plated probe didnt worked, maybe there are cracks or the platinum was too thin, i will recoat it one day, but i need to figure out which additive make the electrolyte coating thicker..

For perchlorates, it is worth measuring only the pH. Only the pH here can goes extremely low, even a negative pH. In the case of NaClO3, you can slowly add enough acid to speed up the electrolysis a little, but the solution should not turn yellow and chlorine should not be released into the environment. No matter how acidic it is, it compensates for itself. It only needs to be measured in the case of perchlorate, but only with a digital pH meter. Mine has a little green liquid in it, it's used in labs, I don't know exactly what kind of electrode it is. This is stored in a neutral liquid. Before first use and if it is adjusted, it must be calibrated with factory pH 7.0 and 4.0 calibration fluids. Can be in solution for a short time. After use, the chlorine must be neutralized immediately in alkaline and clean water. The 40A you are using is enough for a slower 20 liter cell, or a faster 10l cell. Lead dioxide is sensitive to pH, but in the case of platinum, if the pH of the solution is extremely low, it does not matter. From pH 5 to pH -1 can easily be achieved after a day of run time in a perchlorate cell. This should be avoided in the case of lead dioxide, and avoid to  run it in i too high solution with a pH of 14.

Precipitating salt is a sign that the cell is not closing properly. I run these cells outdoors. Chlorine must not accumulate in the room. I don't over complicate the cell, I use a plain glass jar with a plastic lid that can be replaced at any time. The plastic roof wears out over time and needs to be replaced after several uses. I don't usually run it at high temperatures, 45°C is more than enough for it. And if you're making perchlorate, you have to keep the temperature below that. If 1-2 A is calculated for every liter, the cell will still do it. For most of the run time, 0.5 A actually passed through my half-liter cell.

The most important thing is a M3 (using chlorine filter) gas mask with airtight goggles, never open the cell without one. If this solution is boiled, it should also only be used outdoors. You also need rubber gloves for this. Chlorine is an extremely toxic gas, even in small quantities. Inhaling it in small doses, getting it into your eyes or skin, or letting it enter the room should be avoided by all means!

[Psymon89]

The exhaust gas cools trough a suction flask and then bubbles into bicarbonate solution.

The other picture is about how to refill, actuallly i only turn on stirring while refilling. maybe its better to run it the whole time?

Last one is where the whole apparatus is sitting, outside on the balcony, so i think theres no possible way to accumulate gases or the gas entering a room cuz of wind.

Edited April 13 by Psymon89

[Psymon89]

And since 2 days there are Salt cubes forming on the bottom of the reactor, they dont redissolved yet, in the first 2 days there wasnt any precipitate, should i refill "empty" distilled water or saturated solution?

[AustralianPyromaniac]

You should use NaOH solution for scrubbing, not NaHCO3. But in your case it doesn't matter much anyway because its outside. Some chlorine can escape NaHCO3, and it becomes depleted very quickly. 

The salt is nonconductive, so if it bridges the electrodes it will not short-circuit. But it will corrode everything. 

Is this NaCl or KCl? Stirring constantly is best for efficiency for chlorate, but for perchlorate it makes no difference. As KClO3 forms the stir bar will become locked into the bottom and cannot move. For constant stirring, it must be done from above, with a Teflon pass-through stopper like this https://vi.aliexpress.com/item/32917905471.html. For NaCl magnetic stirring from below is ok. 

Your cell is leaking, not sure why, you will have to figure out what is wrong with the engineering. That is a lot of salt creep. For access to the cell, I think the use of a teflon stopper in a hole works really well. The Teflon can make a seal, but is easy to remove and put back. I have put an image below of a design that features a Teflon stopper for access. https://vi.aliexpress.com/item/1005001297134968.html

pH control is very complicated, rather than actively controlling pH, just use a 1% solution of HCl in water to top up the cell, this will prevent pH runaway, but doesn't require complex adjustment. If you want to measure the pH, any probe will be destroyed quickly, unless it is very expensive and uses semiconductor technology. Before testing, if using NaCl, boil the solution and NaClO decomposes. If using KCl KClO is stable to boiling, so drop one small crystal of sodium thiosulpate into your test sample, swirl around, then test. In both cases, the oxidizing compounds are eliminated, but H+/OH- is not effected. Test can then be done with probe or pH paper, but paper is not that accurate. 

 

 

CHLORATE CELL DRAWINGS.pdf

[Psymon89]

i already have a port with teflon screw, just look the pics.

Unfortunately i i got not enough pressure on the teflon-sheets to seal well, the titanium screws was to short to get good force on the seal, thats whys leaking a bit.

anyway if i just put a simple plate on top like mx5kevin said it will leak as well so i think this run doesnt matter since its outside, next run will be FKM-O-Ring instead of PTFE-sheet, they can be compressend and i will see if its sealed or not before starting the run.

Edited April 13 by Psymon89

[mx5kevin]

When bubbled through a solution, hydrogen exerts resistance in the cell. Over pressure builds up in the cell and in many cases the gases do not escape through the tube, but the cell starts to leak. It is not advisable to feed the cell with saturated salt solution, only with plain water, or the solution what used for pH control. If you live in an apartment building, I would be careful when regulating the pH, because a strong chlorine smell will form if the cell is regulated too acidic, which may happen regularly. Within 5 meters this chlorine smell can be very strong. I don't bubble it through anything, but I lead it far away through a very long pipe, at least more than 10 meters long. This can be reduced in one way, so that the acid is added in very small drops and stopped in time. The salt deposits should be washed off using rubber gloves and a bucket water. Never open the cell after pH adjustment, and be very careful not to allow yellowish gas to accumulate on the top, as it is extremely explosive. The cell should always be filled to the point where gases cannot accumulate on a large surface area. Chlorine dioxide is capable of a powerful explosion when mixed with hydrogen and is very sensitive to light. By the power, I mean that it shatters that plexiglass plate with the top of the cell with a very loud sound. And if it explodes in your hand when you open it, it can rip your fingers off, so be careful. If HCl acid is suddenly introduced and the cell is immediately sealed, such an explosion is almost guaranteed. If you adjust the pH and start the cell, don't stay near it afterwards and don't try to do it something with it it by accident. This danger is particularly high when a stable chlorate has formed and hydrochloric acid is added to it. ClO2 with hydrogen is a very powerful gas mixture, much more powerful than ClO2 itself.

[Psymon89]

i controlled this morning, the salt is sealing the cell now, just dry caked salt around the seals and no water anymore.

refilled with plain water instead of saturated, also adjusted the ph to 3.5-4 in the 275ml of refill.

its now at 4.1V @ 41.9A beginning 4 days it was at 3.8-.9V @ 41.5-.8A

 

Edit: filling with ph adjusted water, there was no yellow gas (chlorine) seeable, of course there is production of chlorine but not that much.

the salt caking inside around the electrodes seems to be okay, since its growing around with a ca. 0.5mm gap and not touching the neighbour electrode.

no corrosion on the anodes, no floating particles nothing... seem to be good anodes.

im gonna post a photo of it later

Edited April 14 by Psymon89