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Thanks Deano.

This is an excellent and informative thread

I have a couple of questions.
Can the leach be reused after running through the carbon felt cell?
If so, a miniature cell in a loop with leach wold ensure the leach never get saturated.

Do anyone have a link to where one can buy carbon felt?
 
I'm not sure whether Deano can reply at the moment however I'm now able to answer your questions. 8)

Yes the leech can be reused after stripping.

A cell of the size I built can hold many KG of gold so a smaller one will still hold a lot. Unless you are stripping from very large quantities of base product - i.e. in the many hundreds of grammes your chances of saturating the carbon felt are minimal. You can tell if you do because no fluid comes out of the centre of the cell because it simply cannot get through the felt any more. Edit: I didn't answer your direct question. Yes you can ensure that your leach liquor never saturates although given the quantity of gold that 200g of cyanide in 20 litres can hold it may not be a problem unless you are likely to add more than half a kilo of gold at a time. I believe it will hold roughly 4 times it's raw weight in metals (Chris/4metals/Lou may correct me) and you would have to also factor the weight of other metals stripped, into this amount.

Carbon felt is for some reason not so easy to come by. I had to to a lot of googling to find a supplier who didn't want to charge me £300 per square meter. I have a supplier per "cell sheet" I managed to pay around £14 for 34cm x 30cm . Given how much gold that holds- it's hardly a big issue.

I'd happily supply you with one of my sheets for the price I paid for it plus the shipping cost if that helps?

Jon
 
Jon the one advantage of a larger cell is that you can run solutions to be stripped in larger volume and so recover the values quicker or is my thinking off here :shock:
 
spaceships said:
Carbon felt is for some reason not so easy to come by. I had to to a lot of googling to find a supplier who didn't want to charge me £300 per square meter. I have a supplier per "cell sheet" I managed to pay around £14 for 34cm x 30cm . Given how much gold that holds- it's hardly a big issue.

Jon
Click to expand...

Jon

I have run into the same problem (high cost for the carbon felt) I have everything else needed to build this cell including a 4"X4"X16" piece of high density graphite (for the anode) which I can cut into (4) 2'' anodes

I want to set mine up for winning the copper (& other base metals) from my copper nitrate solutions & then re-using the nitric for base metal digestion again but I am having a hard time justifying the high cost of the carbon felt for a base metal winning application --- do you have a link to the supplier you are getting the better priced per "cell sheets" from :?:

Also I have another question - you are using yours to win your gold (&/or PMs) back from solution - but if it is being won back in the matrix of the carbon felt don't you have to then incinerate the carbon felt to turn it to ash & then smelt it (flux to slag the ash off) or - incinerate to re-leach it (the PMs) from the ash --- or am I missing something here :?:

Kurt
 
spaceships wrote:


Carbon felt is for some reason not so easy to come by. I had to to a lot of googling to find a supplier who didn't want to charge me £300 per square meter. I have a supplier per "cell sheet" I managed to pay around £14 for 34cm x 30cm . Given how much gold that holds- it's hardly a big issue.

Jon


Jon

I have run into the same problem (high cost for the carbon felt) I have everything else needed to build this cell including a 4"X4"X16" piece of high density graphite (for the anode) which I can cut into (4) 2'' anodes

I want to set mine up for winning the copper (& other base metals) from my copper nitrate solutions & then re-using the nitric for base metal digestion again but I am having a hard time justifying the high cost of the carbon felt for a base metal winning application --- do you have a link to the supplier you are getting the better priced per "cell sheets" from :?:

Also I have another question - you are using yours to win your gold (&/or PMs) back from solution - but if it is being won back in the matrix of the carbon felt don't you have to then incinerate the carbon felt to turn it to ash & then smelt it (flux to slag the ash off) or - incinerate to re-leach it (the PMs) from the ash --- or am I missing something here :?:

Kurt
Click to expand...

Hi
I'm curious about what voltage that are used for the cell?
I guess it will create chlorine if it is too high, but if that is fed back to the leach it could be beneficial wouldn't it?

Regarding the felt is it possible to use the same method as they use to make carbon fiber?

Take a sheet or form made from loose felt/wool/cotton.
Evaporate everything else than carbon in vacuum or anaerobe atmosphere in an oven, I can't actually remember temps just now.
I have no idea if it is economically viable, but for the ones that already have furnaces it should be technically possible though.
And one could create whatever form one needs.

How would the felt and/or graphite electrode behave in sulfuric acid ref to Deanos tiocyanate leach?
 
Kurt it depends on what type of solutions you are running in the cell and what metals you have in solution, it will do an excellent job of recovering values from base solutions which can be melted and sold as is or refined if that is your preference , with acidic solutions I believe by varying the voltage/ ampage it can be made selective to a degree or so I believe, trials were been conducted by another firm into how it could be done but assays are needed to check what is been stripped or left.
 
Kurt/Nick

The secret is to have a DC PSU with variable voltage. The maximum current needs to be at a level whereby the requirements never exceed the maximum available current. If you do that you reach an equilibrium in the cell whereby the metals are plating out and redissolving and therefore you have no resulting metal.

As you increase the voltage the current draw will increase. Also, and importantly the level of metal in solution affects the current drawn too. I made the mistake of running the cell the first time at far too low a voltage- I was at 2V with a current draw of around 1A. Not a lot happened. I increased the voltage until there was a definite fizzing in the cell and gas was visibly being produced. It is important to note that I was stripping metals from a non acidic leech solution so I was not producing Chlorine gas, which you will produce from any HCl based solution. In order to get the cell operating for the particular solution I was running the voltage was around 10V with a current draw of around 13A.

Do note that dimensions of your cell i.e. diameter and distance from cathode to anode, along with volume of liquid AND saturation of metals in solution all affect the current drawn. Dean explains this far better than me I am afraid, but safe to say you need to adjust for the conditions you are operating within.

My DC power supply runs a max of 30V and 60A - not a cheap piece of kit. Dean regularly runs at 200 amps.
 
spaceships said:
Kurt/Nick

The secret is to have a DC PSU with variable voltage. The maximum current needs to be at a level whereby the requirements never exceed the maximum available current. If you do that you reach an equilibrium in the cell whereby the metals are plating out and redissolving and therefore you have no resulting metal.

As you increase the voltage the current draw will increase. Also, and importantly the level of metal in solution affects the current drawn too. I made the mistake of running the cell the first time at far too low a voltage- I was at 2V with a current draw of around 1A. Not a lot happened. I increased the voltage until there was a definite fizzing in the cell and gas was visibly being produced. It is important to note that I was stripping metals from a non acidic leech solution so I was not producing Chlorine gas, which you will produce from any HCl based solution. In order to get the cell operating for the particular solution I was running the voltage was around 10V with a current draw of around 13A.

Do note that dimensions of your cell i.e. diameter and distance from cathode to anode, along with volume of liquid AND saturation of metals in solution all affect the current drawn. Dean explains this far better than me I am afraid, but safe to say you need to adjust for the conditions you are operating within.

My DC power supply runs a max of 30V and 60A - not a cheap piece of kit. Dean regularly runs at 200 amps.
Click to expand...

The surface areas of your anode and cathode heavily come into play on this as well Jon.
 
Actually 4metals no they wouldn't. One of the main features of the carbon is the sheer surface area that's available. That increases the efficiency enormously, and that just isn't there in the copper product on the link.

Thanks though.
 
They work getting plating solutions down to 1 ppm and have been around for 30 years. They have a platinized titanium anode. Maybe it wouldn't grab everything first pass but they melt nice.
 
Oh yeah I get that. The way that Dean set this up though it's designed to get it all out on the first pass.
 
If used for pretreating chloride waste solutions, what would be the best and safest way to capture the chlorine gas? Of course I have some ideas, but those are pure theory and assuming (like using Ca(OH)2, NaOH (in the cold) or oxidizing FeCl2 to FeCl3 - as said assuming without knowing how well it works). Is there an easy and definite answer to this?
 
4metals said:
What is your flow rate through the cell. I like those little peristaltics you have mounted on the surrounding enclosure.
Click to expand...

The important part of the flow rate is the outflow and the setting I am currently using is just under 1 litre per hour. Even though that is slow it is because it "safe" to strip all the metals out at that flow rate according to Dean, and I can increase this once my AAS arrives and I can sample the outflow and adjust accordingly. An AAS isn't essential when using this cell but having one allows you to use higher flow rates because you can monitor and sample the liquor.

The input side is set to over 1 litre per hour because the return pipe that you can see limits the volume of liquor in the cell and having the input greater than the output, with it's self regulating return prevents the cell from running dry.

On the MK2 vervsion there will be a switch on the input that shuts off the flow automatically is there is no current flowing through the cell thereby introducing a safety mechanism that allows the cell to be run unattended.

I'll also be using more expensive peristaltic pumps that are more accurate, rather than these chinese fleabay ones.

Does that answer your question properly 4metals? Let me know if you need any more info.

Jon
 
solar_plasma said:
If used for pretreating chloride waste solutions, what would be the best and safest way to capture the chlorine gas? Of course I have some ideas, but those are pure theory and assuming (like using Ca(OH)2, NaOH (in the cold) or oxidizing FeCl2 to FeCl3 - as said assuming without knowing how well it works). Is there an easy and definite answer to this?
Click to expand...

To be honest Bjorn it's not something that I am experienced with and I'd love to know the answer too.

Jon
 
Jon,

Thanks for the response, at 1 liter/hr your thru put for a large volume can be quite some time, I am weighing in my mind the benefits of slow flow one pass on carbon cathode vs a batch in the tank multi pass carbon foam cathode. Other than the obvious need for analytics on the AA to determine when stripping is complete.
 
I quite agree with your thinking.

I process in batches of approx 20l at a time when doing a "leach" so a time factor of less than a day really doesn't create a major problem. Obviously there's also no harm in setting up two cells in parallel and doubling the throughput, if required or alternatively simply building a bigger unit because the cell scales.

Dean's cell is much larger, and processes a lot more per hour.

My own setup will eventually have two cells in series- the second cell to oxidise the leach liquor to water with no waste or hazardous substances.
 
Hi Jon!
What size do your cell have, half of the carbon felt size?
170 x 300 mm?
Seems the dimensions is approximately 60-80 mm diameter and some 200 mm tall?

Have you tried running in reverse polarity?
Do you expect degradation/consumption of the felt when running with reverse polarity?
 
Running in reverse polarity is the actual basis of how the cell was developed. It destroys organics completely in one pass. Yes there is naturally degradation of the carbon felt in this mode however the rate of degradation vs the sheer surface area available means it can destroy an awful lot of organics before it's "spent." 8)

Jon

I must note that credit for this cell goes to Deano not me. I'm merely the first person to build and use it on this forum. His advice is excellent and if you read his thread deeply there are a number of other things that members will benefit from greatly.
 

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