387 replies to this topic

[hashashan]

Andres,
Your cloth is way to big, it is actually not smart to make such an anode. remember that in order to produce perchlorate with it you need to maintain 200ma per sq. cm at least. that means that if you have an anode 10*10 cm youll need at lesat 40 amps in order to start producing perchlorate.
second your current is way to low for such a small anode. youll need to plate at 4ma/sq.cm on the start and then switch to about 20 in order to speed the process up.
Maybe your solution isnt quite good too? how much Pb(NO3)2/liter and Cu(NO3)2/liter you use?

oh yheah and lead dioxide for pasting is easily produced by oxidation of lead nitrate with NaOCl(even 5%) at elevated temperatures(about 50 - 60 degrees) for about half an hour and then purifying the solution by decantation.

Try to avoid any contaminations to your solution like Iron and chlorides.

and for your sake make a smaller anode(really a 50 sq cm is more then enough).

[Anders Greenman]

Thanks!
But regarding the size of my anode, I have a Power Supply capable of delivering about 200A, so the current isn't really a problem. But I will do as you say, and cut my anode in half I think the solution is bad. I lost a small piece of steel in it, so it's probably contaminated and I have no idea how much Lead Nitrate is in the solution! I just poured in Lead Dioxide solution wich is a waste product form the Tetraoxide-HNO3 process. I know it contains about 50g Copper Nitrate though. I think I'l prepare a new solution with the exact amount of nitrate and destilled water. I used tap water because the water here I live is very pure! Will keep you updated!

[hashashan]

dont worry about the water i also used always tap water. the lead nitrate quantitiy is very important you need at least 200g/l i use much more .. i use as much as dissolves.. i'd say 500g/l will be just fine for you. the copper nitrate is not a critical matter as long as your solution is blue you are fine.( it gets less and less blue as the electrolisys starts because of the copper deposition)

about your 200 amps source ... it is great but do you have cables to run that current, a conection to the LD (it is very imoportant, i had several anodes just catching fire from 10 amps due to not very good connection and i used silver) at 200 amps your solutuion will boil within several minutes and we dont want the temperature to rise above 50 degrees.

anyway if you are using a 0.5-3 liter vessel dont use more then 20 amps(it is just not smart)

make sure how much lead nitrate you use. dont leave any acid in your solution.
It will be smart to make some sort of a PH controller to your solution because it gets acidic very fast and that will result a not very good anode (like my own... i am planning to make a new one with PH control)

[Anders Greenman]

I was using a 4L plating bath, but now I will use something alot smaller to save som chems, but still big enough to make a good anode. About 1-2L shold do.
I will weigh the nitrate this time, for sure, but my new connection failed today! The graphite just dissolved as last time despite the heavy PbO2/Polystyrene coating. Will try plastic next time.

I have som very fat cables (the total will be 10mm I.D) capable of carrying currents up to around 300A, so that's okey. I planned using silver connections too, and bought some silver paint (yes, the real stuff) but it was very expensive! I hope this will work.
I know the solution will get very warm at such temperatures, but I'm planning to use an active cooling system and a pretty big cell (at least 4L, prebably 10L if I should run 200A). My 4dl graphite cell did fine with 20A current and water cooling so the big one will probably work.

[marble]

10L @ 200A will get bloody hot (boiling me thinks). Might be easier to run a few cells in parallel.

[Anders Greenman]

Maybe, but I have a very effective cooling system (tank with flowing ice-cold water)! My 20A cell had no problem with it.

[marble]

New cell is working well (aside from the brass connectors eroding into the electrolyte, not good but hot glue solves all) but is the electrolyte supposed to smell strongly of chlorine? got a bad whiff when i was inspecting the anodes and its going to make filtering it a bad experience for my lungs.

[Anders Greenman]

Mine smelled too, during the run and afterwards, but it will disappear within 10 minutes
if you pour it in another container and let it cool. Did both boiling and filtering with no smell whatsoever.

[hashashan]

If your connection gets killed that can only mean one thing .... too much acid
use PH controll .. just dump in some PbO in the worst case .. or put it in from time to time.
use stirring.
and the 200Amps is just not good. its not efficient .. well of course it is faster then 20 amps ... but 20 amps is fast enough and much more efficient and gives you less headache
also teh 20 amps will theoretically give you about 300 grams of chlorate per day (practicaly about 150 if your cell is simple) 150 per day is just fine

[Anders Greenman]

Ah, thanks! Since the chemicals i added contained HNO3 impurities, I wasn't really able to control the Ph. Will do it next time!
The amps is alot, I know. Will take it easy in the beginning and see.

Edited by Anders Greenman, 12 August 2007 - 10:48 AM.

[YT2095]

do any of you add Potassium Dichromate to the chlorate cells to prevent back reduction?

[hashashan]

You cant use dichromate while using PbO2 anodes.
You can ONLY use HF, fluorides or persulfates

[YT2095]

you don`t need lead oxide electrodes in a Chlorate cell though.

I wasn`t addressing PERchlorate cells.

[Arthur Brown]

Seeing UK suppliers of perc is it really a great idea to try to make this at home? There is of course the "achievement factor" but with the effort to pass 20 - 200amps through a cell then purify the product is it really commercially viable?

Also I suspect that commercial electrolysis will be done in series wired cells as there are huge losses in the rectifiers -say 1.2V - and out of 8 volts that is a lot.

[Anders Greenman]

You're right, the losses are huge, but what is the most economical solution? Low voltage will give bad efficiency, but at a lower price per kWh (you pay for watts, not amperes) and in the opposite, high voltage will give good efficiency, but at a high price! And they might be using something other than the usual diode rectifier (maybe thyristor based) wich may give better efficiency.