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Author: Subject: Processing chlorate cell electrolyte
frogfot
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[*] posted on 1-4-2003 at 02:23
Processing chlorate cell electrolyte


Hi, i got a really annoying problem. After preparing chlorate electrolytically i found it hard to remove carbon particles..
My procidure was simple, first i filtered electrolyte through a piece of compressed cotton, this gave a clear green solution. But with a flashlight test one could see the beam through the liquid, which meant that small particles was still present.
After 30 min boiling solution got gradually orange to black. Any clue why this color change happened?
After filtering this i ubtained an orange liquid. Flashlight test showed the same thing as first time though light beam was much weaker..

Is there any way one could filter electrolyte to remove all particles? I heard many documents mention diatomeous earth, is it worth bying? (though i havn't looked for it yet)
Or maby one can leave the electrolyte for a month, maby all particles will settle down?
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[*] posted on 1-4-2003 at 12:30


Can´t help you in terms of your color change, but:

diatomeeous earth = "kieselguhr"= "infusorial earth" = "terra silicea".
It is not exactly cheap, but not really expensive.

But as you suggested, i am also sure that time would do its thing and the particles would settle.

I may be wrong, but personally i don´t think such a small amount of carbon in the final product would increase its sensitivity considerably.




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[*] posted on 1-4-2003 at 13:33


Quote:

diatomeeous earth = "kieselguhr"= "infusorial earth" = "terra silicea"

aka "celite". Aquarium or brewery supply.

but not perlite! :D
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[*] posted on 1-4-2003 at 13:36


Did you add any dichromate by any chance?



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smile.gif posted on 1-4-2003 at 15:35
odd color change


I tried this a looong time ago with NaCl, then converting it to the potassium salt. I too got the bleach green color and tons of carbon crap. For me it more or less resolved overnight and a simple filtering through medium lab filter paper did it just fine. Upon boiling, It remained rather green and I only got a few impure crystals. Never the less when ground with sugar they burnt with a long purple flame which looked interesting.
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shocked.gif posted on 1-4-2003 at 18:05


Purple flame?With Na?

:o:o:o




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blazter
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biggrin.gif posted on 1-4-2003 at 21:18
NaClO3 converted to KClO3


I used KCl to convert the NaClO3 to KClO3 which is MUCH less soluable and would've hopefully precipitated first. As i found it isnt that cut and dry, and some contaminants precipated along with it. But yes I beleive it was the K that gave the purpleish flame.
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[*] posted on 2-4-2003 at 03:32


I didn't used cromates.. but maby cathode is responcible for this, it was usuall iron. Recently i thoat that cell chamber could be responcible for strange color, they're made of polystyrene, and it should react with chlorine. Cells was transparent and had some forry spots after operation.

Well, i forgot about how expencive things are in my country.. BASF, youre maby right, afterall, product looked slightly grey, this shouldn't be a problem :)

Blazter, that mustve been some high quality KClO3 you've made. I heard that color from potassium is jammed very easily by traces of Na, how many times have you recrysallised it?
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sad.gif posted on 2-4-2003 at 12:13
Actually it wasn't that pure


I sort of got impatient with the cell I was running and the anode was getting eaten to nothing pretty fast. IIRC I ran it for something like 60amp hours. Even then it was obvious that it wasn't a very pure product. I came to that conclusion because actual flame tests with the material showed a strong sodium color, though with filtered with cobalt glass some of the flame could still be seen, indicating potassium ions. The crystals also didnt form particularly well, they were sort of pyrimidal or something like that. When I made chlorate from boiling down bleach I assume I got much higher purity crystals because they formed in leaflets, which is characteristic of pure chlorate. On top of this, the pyrotechnic mix I made with it wasn't particularly fast burning. This is a strong contrast with the chlorate from bleach which burns almost as fast as flash.
Hope ya have good luck with your project, and you may need to run your cell again to convert more to chlorate. Remember you can recycle the electrolyte as many times as needed so nothing is wasted!

BTW, for the cell I made was a 200ml glass beaker with a spiral of 14 guage copper wire lining the inside of the beaker.
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[*] posted on 11-4-2003 at 12:46
Just an update


Well, i got totally 217g of product from above named electrolyte. After second recrystallisation i got 181g snow white product:
http://www.geocities.com/frogfot/stuff/chlorate.jpg

It seems that such big mass loss indicates that lots of KCl was present, about 20g. Btw, I used vacuum filtration, it makes wonders.

I have "modified" the processing procidure a bit, i boil it before filtering, this way it can't destroy cotton filter.
Procidure goes like that:

First, pH in crude electrolyte is adjusted to 6, and then it is boiled for 30 minutes. Then it's chilled and filtered through compressed cotton. After it's ready for extraction of product. I found that there are no difference between using pure KCl and a mineral salt (a mix of NaCl and KCl 40:60), well, it gives same mass after first recrystallization.

It seems that used procidure is sufficient to remove those small annoying coal particles (and strange colors). Btw, now im pretty sure that strange color was from polystyrene cell. Next cell will be made of polypropylene and chromates will be used.
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[*] posted on 26-5-2003 at 23:24
chlorate


Tips.

Your yield is going to be mostly salt if you don't use chromates, there is a reason that industrial plants use them, they prevent your product from getting reduced as soon as it is made.

You need to run the reaction at 80-90 degrees celcius, and after you are done running current through it you need to let it sit and react at this temperature for a while.

Adjust the pH to 6 using bleach before your run, bleach is an intermediate.

Pure chlorate crystals are not leaflets, all the chlorate I've ever seen(think thousands of tonnes) is like salt, some of the bigger crystals (I saw some today) are sorta rhomboid.

Carbon is old school, new school is stainless and platinum coated titanium. If you must use carbon you still need chromates, to get it out filter through celite(pool store).

A high currrent and low voltage is used, the cell banks in an industrial plant are at about 3.5 V per cell, and well over 100,000 amperes.

Anything else pertaining to chlorate manufacture? For the non totse members, I work at a chemical plant where one of the main products is chlorate.
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[*] posted on 29-5-2003 at 12:41


ph6 is acid, bleach is a base. Possibly you were indending to say ph9 ish? I think mild base is best, but if it gets too high the carbon rod erosion rate suffers, as its OH- catalysed. The ph of the solution should be maintained by adding dilute HCl as needed during the electroylsis.
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[*] posted on 30-5-2003 at 17:59
perhaps


Perhaps I should have said that in the industrial plant they use hypochlorite to adjust the pH. They also use HCl.
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[*] posted on 6-6-2003 at 00:23


Soz, this is kinda late reply but i couldn't let it be..

Chromates is used to rise efficiency with 10-20%, this is alot for an industry but not in home cell. However i ubtained some potassium chromate and will use it in next cell.

"Your yield is going to be mostly salt if..."
Do you mean i will yield NaCl after a recrystallisation? Impossible, then it wouldn't precipitate with temperature fall.

80-90*C is inaproppriate for carbon electrodes, they will corrode at great rate. Recommended temperature is 40*C.

Why addjust pH with bleach? This simply wouldn't be economical. HCl do the trick for me, and most factories :) 2kg sodium hypochlorite cost 40$ here.

Carbon is used in many chlorate plants even today, since it's cheap. Titanium would cost here same as gold.... :(

I got one question. I heard that graphite plants have a continious flow of electrolyte through a hypochlorite converting chamber, where it's heated to 90*C. How big current per volume requiers this? I mean, if my new cell will operate at 8A/liter, do i need to stop electrolysis and heat electrolyte from time to time?
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cool.gif posted on 30-6-2003 at 03:58
Chlorate!


I suggest putting in some AN or any ammonium salt in the electrolysis vessel - equimolar quantity of NH4+ to ClO3-. These form a nicely insoluble precipitate.
It's OK as long as you're happy with the explosive NH4ClO3, which doesn't give the flame a colour.:cool:
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[*] posted on 30-6-2003 at 07:03


Can anyone tell me, what apart from pH, influences whether Cl2 or ClO3- is produced (I know that chlorine disproportionates faster in alkaline solutions)?:o:o:o
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[*] posted on 30-6-2003 at 09:03


actually, chlorine doesnt disproportionates in alkaline solution, it reacts with hydroxide ions forming hypochlorite ions, this reaction goes faster the higher conc of hydroxide it is.


Hypochlorite disproportionates to chlorine and chlorate, maximum speed is at pH 6-7 because it is a reaction between hypochlorous acid (HClO) and hypochlorite ion. Higher pH , there are virtually none acid, lower the acid decomposes into Cl2 and Cl-. higher temperature also affect the reaction positively with a maximum around 70-80 C.

/rickard
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[*] posted on 1-7-2003 at 06:46


"actually, chlorine doesnt disproportionates in alkaline solution, it reacts with hydroxide ions forming hypochlorite ions, this reaction goes faster the higher conc of hydroxide it is."

Well, the reaction between chlorine and OH- to form ClO- and Cl- is called disproportionation:mad:.
Also chlorine could directly disproportionate to ClO3- and Cl-, as it can from ClO-.
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[*] posted on 1-7-2003 at 08:52


Well, the reaction between chlorine and OH- to form ClO- and Cl- is called disproportionation

Not true. A disproportionation reaction is a reaction where ONE compound reacts with itself to form 2 compounds with different oxidation states of a central atom. In hypochlorite to chlorate, some of the chlorite gets oxidized to chlorate, will some chlorite will be reduced to chloride.




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mad.gif posted on 3-7-2003 at 04:33
Disproportionation


Not, true!
A reaction where a compond or an element react with another compound or itself, where a certain element gets both oxidized and reduced is called disproportionation.
In CHEMISTRY BOOKS the reaction of Cl2 with alkalis is called disproportionation, so is that of sulfur.
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[*] posted on 7-8-2003 at 02:23


All the fine tuning (pH control by acid or base, adding dichromates or other compounds to inhibit cathodic reduction of ClO3- etc.) is not a must when it comes to chlorate production on a domestic scale!
Believe me I have produced several kg of KClO3 by electrochemical means and after trying all those methods to improve productivity I can say with absolute confidence that it's not worth the trouble! The effect
of those additives on the final amount produced can only yield some results on an industrial scale at home the difference is so small that there is no need to add anything into the solution besides the chloride.
I used a concentrated solution (at room temperature that is) of fertilizer grade KCl in regular tap water. Tap water contains calcium compounds which inhibit the ClO3- reduction at the cathode just like dichromates do.
There is no need to use NaCl solution and then convert it to KClO3. Smart books say the production rate is higher in NaCl but in the end it's unnoticeable and there's a ton of trouble and more things can go wrong. So just keep it simple and use KCl to begin with!
I took 'bout 5L of straight KCl solution a 5*5*10cm graphite anode and a 5*10cm stainless cathode (works great, doesn't corrode!!) and ran 20A of current through this setup for at least 12 hours.
The reaction temperature is around 40-50C and is kept by the current and the cooling system. Just tipped the bottom of the 5L cell into running water (a creek that is!!), works great he-he :) The temp is really not critical as long as it's over 40C.
As exp shows this system is rather foolproof as long as one keeps the temp over 40C the current over 3A/per liter of electrolyte and the additives out of the cell!
There really isn't much sense in prolonging the
reaction time over 24 hours. Taken the same amount of KCl and current that is! After the 12 hours I get about 100-150g of KClO3 and it's enough for my needs. Don't take these numbers as an exact reference but about 8 cycles yield a kg of KClO3 so the single cycle must produce about that amount.
:D
When it comes to filtering there's only one solution to get all the fine crap out of the solution - glass wool! I use standard insulation wool (the yellow stuff in the walls to keep warmth in house) it costs nothing and filters like a mother!! I usually collect the dirty results of 4 to 5 cycles and
then hot filter them once and the final product is white as snow and a real eye-candy!

Damn I've been blabbering on....
Well so long!
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[*] posted on 8-8-2003 at 05:58


Well... if anyone wants to try NaClO3 for a change? More oxygen per gram and a "golden flame". :)
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[*] posted on 13-8-2003 at 00:28


Yup! And it's hygroscopic and readily soluble in water, meaning that you will have alotta trouble with separation from chlorides and drying.
But it's soubility makes it a perfect starting material for producing other chlorates that have a low solubility (metathesis reactions) BaClO3 or KClO3...
When producing KClO3 it's better to start with KCl and not mess around with the metathesis! It will save time and trouble and no residual Na ions will be introduced into the final product.
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[*] posted on 4-3-2004 at 11:21


Could ytou hand some KCLO3 by a string or wire into your electrolyte to form one big crystal? The electrolyte would be the mother liquor and the KCLO3 would be the seed crystal. It should work, but I cant back it up cbecause I havnt tried it before.


I belive there is a section on wouter's page that explains why you shoudnt start out with a KCL brine solution as your electrolyte.




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[*] posted on 4-3-2004 at 11:51


Sorry for the late reply, countrymate, but is a Pt anode out of the question? You could use normal 18-10 stainless as the cathode (use a baking bowl and a hacksaw...) and a platinum wire as the anode. I ordered one 3 weeks ago, it should arrive soon. A 300mm long wire with a diametre of 0.8mm. Cost: about 1500SEK. But it will outlive me and you, and you won't have problems with carbon particles.



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