Electrochemistry trying a new cell concept

[Geo]

hey guys, i need some help with the chemistry on this one.im sure its very simple but im having trouble grasping it. modtheworld44 has contacted me with a collaboration on trying to find an electrolyte that will dissolve pins gold and all that is cheap and easy.im using carbon gouging rods as the electrodes and sodium hypochlorite as the electrolyte.
my assumption was that keeping the amps low enough,i could use electrolysis to create chlorine gas only in the vicinity of the anode dissolving the anode material.right away i could tell the amps was way too high because the carbon rods started to break down and chlorine fumes were being emitted in a fog. after i disconnected the power, the solution kept off gassing for several hours.
i want the chlorine to be produced slow enough that is used up as it made. if we can figure out how to make this work,it could be a way to dissolve pins without using AR in a set it and leave it operation.

any thoughts about what happens to sodium hypochlorite during electrolysis? also, how many volts and amps could be used to produce the effect im looking for, even if it can be done.

 

[butcher]

What about just trying brine a saturated salt NaCl and lowering the current, you may also find a membrane useful.

Rock salt can be used to generate the chlorine or the hypochlorite; it can also form sodium hydroxide, some of which can help to keep chlorine in solution (reforming salt NaCl).
Normally they use salt bridges or membranes to split the cell to keep products separated.

If current is high hydrogen will gas off at cathode (H2O splitting to H and OH), Hydroxide and sodium would combine to form NaOH sodium hydroxides, chlorides at anode will be oxidized to chlorine or hypochlorite, higher the current and temperature the more the chlorine would gas off depending on current, concentration, and temperature, low current, and chilling the cell may help here to keep chlorine in solution.

Temperature of the cell can be a big factor as well as current and concentration of what products will form (especially true when using chloride electrolyte).

I am a little confused on why you need the carbon for both electrodes; unless carbon is just for the cathode I would make the pins the anode.

Connections electrically for the pins would be a problem I see.
And the fact that the base metals would preferentially be attacked, although it could be used to break down the pins to a metal powder.

Maybe some inert connection to the pins, maybe something like a hole drilled in the bottom of glass for, or something like a gallon bottle neck jug with the bottom cut out ( you can cut glass several ways, a hot wire using electricity to heat the wire, and ice to cut the glass, or a glass cutter in a jig to roll the bottle on), the idea is to have the anode connection at the bottom of the cell, some inert metal (inert to the electrolyte used), coming up through the bottom of the cell or glass and for the pins to sit on, maybe something like titanium eye glass frames can be used for connection to pins, or carbon graphite but it would need to be easily replaced, high temp silicone gasket seal or some type of epoxy to seal glass, with the jug maybe a plastic lid with Teflon gasket

Maybe also try a nitrate salt as an electrolyte (used copper nitrate solution) to break the anode to powders.



You can make a variable resistor in series with your cell to adjust the current, a simple one can be made from an old electric heater, for experimenting with you can just wire the positive of your power supply to one end of the heater coil (NiChrome wire) and clip an alligator clip with a jumper wire to the anode of your cell, for more or less current to your cell move where the alligator clip is on the heater wire, the series light bulb can also be used with this, you can also use this same principle to lower voltage to your cell, using the resistor (heater wire) in parallel with your cell.


I think adding copper to increase copper content, and making copper anodes and just using a copper sulfate cell would work better than most anything, the added scrap copper maybe could come from cemented copper powder from our processes, setup cost and the cost of furnace fuel may be the problem with this idea.

An Idea use a two cell operation, one of a sulfate solution to dissolve the copper (pins) as the anode into the electrolyte solution, then this copper loaded electrolyte, is pumped to a second cell where an inert anode plates out copper and lowers copper content of electrolyte, this solution is recycled back to the primary cell to pick up more copper, with electrolyte cycling through these two cells, (a settling cell or chamber or membrane between these two to catch insoluble gold from solution, or using anode bagging.

 

[cnbarr]

I'm not near as versed as butcher is on the subject but he is right look into a membrane. I've been working on a similar cell design, mainly for recovery from pyrolysed ic's., I'm using a platinized anode and a titanium cathode. I haven't got the result I want but it has been positive results. I have a few patents I'll post when I get a minute, that may help.

 

[etack]

Why not attack the Cu alloy and leave the Au to be caught in an anode bag? If you used a nitrate solution the gold won't be affected and the other metals should plate out, right? This would be similar to that weak nitric acid cell that was discussed about 2 weeks ago.

Eric

 

[Geo]

Butcher, thank you very much. i had followed a couple of threads about cell construction with a membrane (i think one of them was Deano's).making the anode bars really is no problem and honestly i was trying to come up with something a new member could work with quickly (like fingers in AP).im sure that finding the right electrolyte is key. i will try all the things you have listed. i have a large variac i was thinking about incorporating. ill try SSN and copper nitrate. i may even try sodium nitrate. i was using two electrodes.one as the cathode and the other was in contact with the pins. i was thinking about using a porous clay pot to catch any anode slimes.

thanks cnbarr and etack for the replies.im always trying to find an easier or less expensive way to do things. for me, it would be simple to toss it all in AR and clean up the mess (i have before) but im really trying to help the new guys.

cnbarr,im looking forward to seeing whatever you can show us.

 

[nickvc]

Geo I'm no chemist so this idea might well be rubbish but have you tried diluting the electrolyte so there's less chlorine to gas off, I'm thinking it might be similar then to the sulphuric cell which only dissolves the gold by the annide where the persulphuric acid is produced, I'm sure there will be some gassing off but it might be reduced to a more controllable amount.

 

[Geo]

thank you nick,i havent thought of that.as a matter of fact,i was using extra strength bleach at almost 9% sodium hypochlorite. diluting it may be something that will help.at first i was using a small adapter that was 5v @ 1.8 amps. it really gave off some chlorine at that. then i thought that it may dissolve faster if i went up in power, so i went to 12v @ 6 amps. it chewed up the gouging rod pretty badly.these electrodes are made to cut metal using plasma and i thought it would hold up better than that. im not sure what reaction was taking place after i cut the power but it continued to make big bubbles for a couple of hours.mind you that the solution had no material in it,nothing. i removed the pins and the electrodes and the bleach continued to bubble happily along for at least two hours.

 

[butcher]

My thought on the two electrodes, where they face each other they maybe just pass current between them (the anode) many not just carry current from the power supply down to the pins (taking the path of least resistance), what I am tying to say I am having a hard time explaining, You may need to shield the (carbon) anode exposed above the pins (in eyesight of the cathode), Hmm gold wire basket or anode connection, platinum, (we can dream can't we), or another metal inert to the electrolyte, I do not think carbon would hold up well if there is a lot of gassing at the electrodes.

Maybe an electrolyte like copper nitrate or copper sulfate, an titanium anode basket the turns and rotates in solution, (BBQ meat rotating motor) knocking off loosened gold, as the pins tumble and scrub each other as electrolyte and electrolysis undermines gold by oxidizing the copper and nickel.

Take caution Geo, with electrolyzing or oxidizing (chlorides), hypochlorites, or even the higher oxididized chlorates and compounds can form, beside the poisonous gas it is possible to form explosive gases or mixes, (some time oils) or high oxidizers making things highly flammable, also hydrogen from the water can form.
Some industrial explosions have occurred in plating and electrolysis operations, run by professionals that understood the chemistry and dangers.

 

[Geo]

thanks Butcher. i have already made up my mind to abandon the sodium hypochlorite as an electrolyte.

what about Oxalic acid? any hidden dangers with this? here its cheap.

 

[butcher]

I havent studied it much, and have no clue how it would react in electrolysis, oxalic acid H2C2O4 is a carbon based compound, I think they make oxalic acid by oxidizing sugar with nitric acid (that alone sounds very dangerous to me).

 

[FrugalRefiner]

This reminds me a little of a cell dallasgoldbug was working on. You may get some ideas from his thread Muradic acid w/Carbon electrodes Hydrogen/Chlorine process.

The thread died out and he wasn't on the forum for a long time, although I did see him post not that long ago.

Dave

 

[Geo]

This reminds me a little of a cell dallasgoldbug was working on. You may get some ideas from his thread Muradic acid w/Carbon electrodes Hydrogen/Chlorine process.

The thread died out and he wasn't on the forum for a long time, although I did see him post not that long ago.

Dave

wow.great thread and a good read.thank you FrugalRefiner. this is the solution i have been looking for. ill gather the material and see if i can pick up the torch and carry on with this experiment.

 

[g_axelsson]

Just a thought that struck me about NaCl as electrolyte.

As I understand it, this is the way you create hypochlorate. One of the side effects of this cell is that the pH is going up as the cell is running. Then if we have other metal ions in solution it should start to precipitate metal hydroxides and we would get a big mess. To run a cell like this for longer times we need to adjust the pH down, either by replacing some of the electrolyte continuously or adding HCl to lower the pH.

I think there was someone that were building a cell like this 3-4 years ago, complete with pictures and all here on the forum.

Göran

 

[FrugalRefiner]

wow.great thread and a good read.thank you FrugalRefiner. this is the solution i have been looking for. ill gather the material and see if i can pick up the torch and carry on with this experiment.

I guess all these months of reading through all the old posts is starting to pay off. I found the topic very interesting and was disappointed it just died. It would be great if you can get it to work! 8)

Dave

 

[cnbarr]

Hey Geo,

Here are the patents I told you about, the first one being the most prevalent, but the others are quite informative as well. I based my cell mostly on the first patent, my theory was to find a better way to recover from pyrolyzed ic's and other pyrolized material.

I have had a some success with it but not enough to call it a winner yet, I believe if it can be fine tuned it will drastically change the the recovery process for ic's and the like as well as other low grade material recovery. With all the great minds here I know it is possible if we bang our heads together and see what happens!!! :mrgreen: Hope it helps spark some ideas?

 

[lazersteve]

Oxalic acid is a carcinogen so I would stay away from it.

Steve

 

[ericrm]

thanks Butcher. i have already made up my mind to abandon the sodium hypochlorite as an electrolyte.

what about Oxalic acid? any hidden dangers with this? here its cheap.

Geo can you elaborate on why you have abandonned the sodium hypochloride cell? also did you had any good result in other cell ? i am curently trying the hcl as an electrolite on kovar pin cpu . i let the voltage very low but i get a very mossy greyish/pinkish deposit, solution have been tested negative for gold with stannous.

it seem that the chlorine rather than attack the gold plating just dissolve base metal ... im wondering if ion cement even when they are moved by electric current? ,if so theyr is no way that any acidic containing aucl in electrolite will work to plate the gold out.

is theyr an electrolite that will passivate the metal under the pin so gold wont cement back but still produce aucl? or maybe an other platable gold salt?

i know that iodine can do it but after that i will be stuck with copper iodide contamined waste wich isnt better...

 

[Geo]

eric, these were the problems i was trying work around.i did try several configurations and none really did what i was expecting. most was as you observed, the base metal was attacked first and left the gold partially digested.i didnt try the SSN but i have all the parts to try. let me rig something together and ill let you know.

 

[solar_plasma]

Oxalic acid is a carcinogen so I would stay away from it.

In europe it isn't. Maybe buy it there? :lol:

 

[Traveller11]

Just a thought that struck me about NaCl as electrolyte.

As I understand it, this is the way you create hypochlorate. One of the side effects of this cell is that the pH is going up as the cell is running. Then if we have other metal ions in solution it should start to precipitate metal hydroxides and we would get a big mess. To run a cell like this for longer times we need to adjust the pH down, either by replacing some of the electrolyte continuously or adding HCl to lower the pH.

I think there was someone that were building a cell like this 3-4 years ago, complete with pictures and all here on the forum.

Göran

This paper was written in the 1890's, prior to chlorine being replaced by cyanide leaching.

http://www.miningandmetallurgy.com/metallurgy/electrolytic-precipitation-gold