Use of Titanium as anode basket/cathode?
Use of Titanium as anode basket/cathode?
Hi all, I've been lurking around the site for a while just soaking up knowlegde as one does, I have also just been gathering my materials and equipment and scrap. I'm mainly interested in silver and will treat it as a hobby/investment although i have amounted a small amount of gold scrap which i will try afterwards. I currently have a few thousand ounces of silver to process. I would say an equal amount of sterling to that of 50% coinage.
I intend to first use nitric to attain the higher purity and then melt down (I managed to find a CM350PB Tilting crucible furnace with an A10 crucible, so hope this wont be too big) in to anode bars to further refine through electrolysis.
My first question is, does or have any of you used titanium baskets or cathodes in your silver cells?
Thanks
Jon Hi Sam,
Good question, I had just read that industrial refiners and electroplaters prefer to use titanium, whether that's true or not i'm not 100% but have been on a few site where the titanium is used and i managed to buy myself a pre-fabricated anode basket made from Ti which fits a nice anode bag and seems neat and hassle free. Using this I assume I can just drop the silver anodes into the basket (bag goes on the outside) and make the connection to the basket rather than the silver, and keep placing another silver bar on top each time. The basket is 1"x2"x5" so plenty room. I'll be using a 5l cell with a 0-6A / 0-30v bench supply.
Although the conductivity of Ti will probably mean I still need a connection to the silver, this is why i'm asking if anyone tried it?
Just trying to keep things neat and error free really.
Jon You have to consider what your reasons are for using titanium.
Electroplaters use titanium (sometimes) because:
1. it lasts longer than most of the alternatives in their systems. That reduces their downtime from having to replace "furnishings." Over the long run titanium can be less expensive for them.
2. titanium in most commercial electroplating baths doesn't corrode significantly so it doesn't poison their bath. Poisoned bath = off spec products = rework or loss.
Some commercial electrowinning/refining processes use titanium anodes (and occasionally cathodes) simply because it is the only commercial product that can survive their operating conditions. So, they HAVE to, or they don't make product and don't make money. If you want to know more, you can google "dimensionally stable anodes", which are titanium plates coated with various precious metals, rare earths etc. so it doesn't corrode away so quickly and to change the activation energy of surface reactions.
However, a typical silver cell (like a Thums-Balbach cell) isn't actually there to "refine silver." That is just a byproduct of its main purpose - TO MAKE MONEY. So, we try to use the cheapest technically feasible materials we can. That reduces capital and operating cost = more profit. A silver cell actually operates in pretty mild conditions, so typically stainless steel (actually, carbon is used industrially) is sufficient for a long time. Stainless costs 1/10 or less what titanium costs, and is much more readily available. You can use titanium - it just isn't optimum from a "make money" standpoint.
I recall that Electrometals was using dimensionally stable anodes (titanium-based) in their flow through cells for silver recovery in Merrill-Crowe plants (that is primary silver recovery, not refining, from cyanide solutions - the electrolytic cells replace the zinc dust that is conventionally used in that process). That allowed their system to survive a lot longer than conventional anodes and cathodes, but that is a very different environment than the standard silver REFINING cell. Also, I don't know if any operating plant has actually adopted the Electrometals process, likely due to cost issues.
As for conductivity, titanium is plenty conductive. The thin oxide layer doesn't cause issues with electrochemical reactions. It is actually more conductive than stainless, so resistance losses are lower.
Best Regards, Gerald The advantage of a titanium basket is it eliminates the need to drill anodes to hang them and it also eliminates the need to remelt anode stubs. They can be used in a vertical Moebius cell. Some say they have a higher electrical resistance than anodes on hooks, that has never been an issue for me.
I have had problems with some bars containing higher gold concentrations causing the slime coating to adversely effect electrical contact of the bars in the basket.
My best luck with them came from using typically cast anodes for all but 1 anode space where a titanium basket was used to eliminate remelting the stubs. Thanks for the replies guys. Initial cost isn't really that much of an issue for such a small item for me, as I assume it will last the lifetime of what I'm willing to do, if not however i will try other materials like SS, I also have a lot of 316L at my disposal (and 304/L, 316, 321, 301, 409 etc...) I work in the petrochem/oil and gas construction business so we have an abundance of scrap materials all over. However as you suggest it's easy and inexpensive to buy over the counter anyway.
4metals, thanks for putting my concerns to bed, i was hoping that i could just 'drop' the silver bar anodes into the basket and away i go, i should be able to get 30oz bars in there, or even 2 or 3 10oz bars.
Now for the cathode........
Cheers
JV Have experience with both titanium anode baskets and SS cathodes.
Ti baskets will work well and they do not corrode easily, just do not overheat cell (>160 F or so) as that will cause rapid corrosion of basket.
SS cathodes have always worked well for me and typically last years. The only corrosion problems I have had are when the contacts get corrosion buildup and cause hot spots, then the cathode tends to corrode.
Good luck.
By the way, if you start with anodes <90% Ag and balance Cu, expect your electrolyte to become Ag depleted very quickly, 1-4 days. Meaning you need to plan for electrolyte replacement. To get decent purity Ag your electrolyte should be at least 50 g/l Ag and keep the Cu <100 g/l I am using CP Grade 2 titanium for my silver cells, about 14 gauge thickness.
The issue with using an anode basket made from titanium is that it has a higher resistance, causes some hydrogen over potential to build in your silver cell, and decreases speed of electrorefining.
I am keen to see how that goes for you though.
FYI, your titanium is fine if it is CP and in an oxidizing environment. Poe is only right if you're using sulfuric acid, hydrofluoric, or caustic solutions. Concentrated HCl will attack it too but as long as you keep an oxidizer in there (i.e. nitric, or HCl/Cl2 or aqua regia) the titanium is safe.
Source: my 300 gallon titanium reactor that's had nitric acid in it as well as aqua regia and 8 years using the hell out of titanium.
Louis Hi, I'm a newbie to this board, and a newbie to refining. As for using a titanium basket, I'm refining silver with the IShor system. I had a custom made basket for the anode and it works well, for 2 reasons.
1) It keeps the electrical connection away from the corrosive environment. 2) It maximizes the anode capacity I can keep in the solution, and I drop in ingots as needed so the amperage can run at a constant level.
They sent me a bag for it as well, so I keep it wrapped within that too. As for the cathode, I don't use a bag as the IShor "Instructions" indicate. I use 2 silver bars attached to a graphite rod. Again, this keeps the rectifier connection out of the chemical drama so to speak, and makes a good handle when I pull out the cathode for the harvest. I place a glass bowl underneath the cathode for the 'drop off' that falls into the solution. Using a bag on the cathode didn't work for me, I just ended up with silver growing through the bag.
I intend to first use nitric to attain the higher purity and then melt down (I managed to find a CM350PB Tilting crucible furnace with an A10 crucible, so hope this wont be too big) in to anode bars to further refine through electrolysis.
My first question is, does or have any of you used titanium baskets or cathodes in your silver cells?
Thanks
Jon Hi Sam,
Good question, I had just read that industrial refiners and electroplaters prefer to use titanium, whether that's true or not i'm not 100% but have been on a few site where the titanium is used and i managed to buy myself a pre-fabricated anode basket made from Ti which fits a nice anode bag and seems neat and hassle free. Using this I assume I can just drop the silver anodes into the basket (bag goes on the outside) and make the connection to the basket rather than the silver, and keep placing another silver bar on top each time. The basket is 1"x2"x5" so plenty room. I'll be using a 5l cell with a 0-6A / 0-30v bench supply.
Although the conductivity of Ti will probably mean I still need a connection to the silver, this is why i'm asking if anyone tried it?
Just trying to keep things neat and error free really.
Jon You have to consider what your reasons are for using titanium.
Electroplaters use titanium (sometimes) because:
1. it lasts longer than most of the alternatives in their systems. That reduces their downtime from having to replace "furnishings." Over the long run titanium can be less expensive for them.
2. titanium in most commercial electroplating baths doesn't corrode significantly so it doesn't poison their bath. Poisoned bath = off spec products = rework or loss.
Some commercial electrowinning/refining processes use titanium anodes (and occasionally cathodes) simply because it is the only commercial product that can survive their operating conditions. So, they HAVE to, or they don't make product and don't make money. If you want to know more, you can google "dimensionally stable anodes", which are titanium plates coated with various precious metals, rare earths etc. so it doesn't corrode away so quickly and to change the activation energy of surface reactions.
However, a typical silver cell (like a Thums-Balbach cell) isn't actually there to "refine silver." That is just a byproduct of its main purpose - TO MAKE MONEY. So, we try to use the cheapest technically feasible materials we can. That reduces capital and operating cost = more profit. A silver cell actually operates in pretty mild conditions, so typically stainless steel (actually, carbon is used industrially) is sufficient for a long time. Stainless costs 1/10 or less what titanium costs, and is much more readily available. You can use titanium - it just isn't optimum from a "make money" standpoint.
I recall that Electrometals was using dimensionally stable anodes (titanium-based) in their flow through cells for silver recovery in Merrill-Crowe plants (that is primary silver recovery, not refining, from cyanide solutions - the electrolytic cells replace the zinc dust that is conventionally used in that process). That allowed their system to survive a lot longer than conventional anodes and cathodes, but that is a very different environment than the standard silver REFINING cell. Also, I don't know if any operating plant has actually adopted the Electrometals process, likely due to cost issues.
As for conductivity, titanium is plenty conductive. The thin oxide layer doesn't cause issues with electrochemical reactions. It is actually more conductive than stainless, so resistance losses are lower.
Best Regards, Gerald The advantage of a titanium basket is it eliminates the need to drill anodes to hang them and it also eliminates the need to remelt anode stubs. They can be used in a vertical Moebius cell. Some say they have a higher electrical resistance than anodes on hooks, that has never been an issue for me.
I have had problems with some bars containing higher gold concentrations causing the slime coating to adversely effect electrical contact of the bars in the basket.
My best luck with them came from using typically cast anodes for all but 1 anode space where a titanium basket was used to eliminate remelting the stubs. Thanks for the replies guys. Initial cost isn't really that much of an issue for such a small item for me, as I assume it will last the lifetime of what I'm willing to do, if not however i will try other materials like SS, I also have a lot of 316L at my disposal (and 304/L, 316, 321, 301, 409 etc...) I work in the petrochem/oil and gas construction business so we have an abundance of scrap materials all over. However as you suggest it's easy and inexpensive to buy over the counter anyway.
4metals, thanks for putting my concerns to bed, i was hoping that i could just 'drop' the silver bar anodes into the basket and away i go, i should be able to get 30oz bars in there, or even 2 or 3 10oz bars.
Now for the cathode........
Cheers
JV Have experience with both titanium anode baskets and SS cathodes.
Ti baskets will work well and they do not corrode easily, just do not overheat cell (>160 F or so) as that will cause rapid corrosion of basket.
SS cathodes have always worked well for me and typically last years. The only corrosion problems I have had are when the contacts get corrosion buildup and cause hot spots, then the cathode tends to corrode.
Good luck.
By the way, if you start with anodes <90% Ag and balance Cu, expect your electrolyte to become Ag depleted very quickly, 1-4 days. Meaning you need to plan for electrolyte replacement. To get decent purity Ag your electrolyte should be at least 50 g/l Ag and keep the Cu <100 g/l I am using CP Grade 2 titanium for my silver cells, about 14 gauge thickness.
The issue with using an anode basket made from titanium is that it has a higher resistance, causes some hydrogen over potential to build in your silver cell, and decreases speed of electrorefining.
I am keen to see how that goes for you though.
FYI, your titanium is fine if it is CP and in an oxidizing environment. Poe is only right if you're using sulfuric acid, hydrofluoric, or caustic solutions. Concentrated HCl will attack it too but as long as you keep an oxidizer in there (i.e. nitric, or HCl/Cl2 or aqua regia) the titanium is safe.
Source: my 300 gallon titanium reactor that's had nitric acid in it as well as aqua regia and 8 years using the hell out of titanium.
Louis Hi, I'm a newbie to this board, and a newbie to refining. As for using a titanium basket, I'm refining silver with the IShor system. I had a custom made basket for the anode and it works well, for 2 reasons.
1) It keeps the electrical connection away from the corrosive environment. 2) It maximizes the anode capacity I can keep in the solution, and I drop in ingots as needed so the amperage can run at a constant level.
They sent me a bag for it as well, so I keep it wrapped within that too. As for the cathode, I don't use a bag as the IShor "Instructions" indicate. I use 2 silver bars attached to a graphite rod. Again, this keeps the rectifier connection out of the chemical drama so to speak, and makes a good handle when I pull out the cathode for the harvest. I place a glass bowl underneath the cathode for the 'drop off' that falls into the solution. Using a bag on the cathode didn't work for me, I just ended up with silver growing through the bag.
The advantage of a titanium basket is it eliminates the need to drill anodes to hang them and it also eliminates the need to remelt anode stubs. They can be used in a vertical Moebius cell. Some say they have a higher electrical resistance than anodes on hooks, that has never been an issue for me.Can we use titanium hooks for copper anode to avoid getting anodes stubs, so we make all the copper anode inside the electrolyte? is it possible? Does the titanium hooks surface get oxidized with copper sulphate solution so it make high resistivity and low conductivity in the cell?
I have had problems with some bars containing higher gold concentrations causing the slime coating to adversely effect electrical contact of the bars in the basket.
My best luck with them came from using typically cast anodes for all but 1 anode space where a titanium basket was used to eliminate remelting the stubs.
The main points of the use of titanium anode
As a professional supplier of titanium electrodes, our experience is that the electrolyte should be stable, especially not containing hydrogen ions and fluoride ions, otherwise it will seriously corrode the titanium substrate. Before the electrolyte enters the electrolytic cell, a filter device should be added, and it should not contain metal particles larger than 0.1mm, so as to avoid excessive accumulation and cause short circuit of positive and negative electrodes. The cathode attachment should not be too thick to avoid short-circuit breakdown of the cathode and anode due to too small electrode spacing or sharp metal formation. Reasonably adjust the cathode and anode spacing, generally 5 ~ 25mm. Try to avoid the use of guide electrodes, which will easily cause the coating to peel off and affect the service life. When stopping, try not to soak in the solution while in power-off mode. Add a small current of about 5A to protect the cathode plate. When pickling or cleaning the surface of the electrode plate, pay attention to protect the surface and do not clean it with sharp objects. When the electrolyte is working, the temperature should not be too high. A reasonable temperature is 25-40 degrees Celsius. Pay attention to the current density when working and keep it within A/m2. If the current is too large, the reaction will be very violent, which will affect the life of the electrode.
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