Think it will work on gold plated material?
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Chemical Things which may be of interest to members
- Thread starter Deano
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When developing this leach the standard test material was gold foil cut to size so that a direct comparison could be made between different leach conditions.
If it digests gold foil it would take off plated gold, there may be some interaction with base metals present.
This is not the all singing all dancing method for gold leaching, it is another tool in the box.
There will certainly be cases where this method is not suitable under certain conditions, I was just wanting to get the method out so that people could do their own testwork and develop a list of suitable and unsuitable conditions.
I could do leach tests for weeks and still not include all the test conditions that members use.
Please note that sodium thiosulfate is also deliquescent, it does so at a much slower rate than ammonium thiosulfate, I did not make this clear previously.
Moral is to keep thiosulfate containers properly capped, do not have open containers left around.
Deano
If it digests gold foil it would take off plated gold, there may be some interaction with base metals present.
This is not the all singing all dancing method for gold leaching, it is another tool in the box.
There will certainly be cases where this method is not suitable under certain conditions, I was just wanting to get the method out so that people could do their own testwork and develop a list of suitable and unsuitable conditions.
I could do leach tests for weeks and still not include all the test conditions that members use.
Please note that sodium thiosulfate is also deliquescent, it does so at a much slower rate than ammonium thiosulfate, I did not make this clear previously.
Moral is to keep thiosulfate containers properly capped, do not have open containers left around.
Deano
So which is it you are talking about here Deano?
Thiocyanate? Or Thiosulfate?
Thiocyanate? Or Thiosulfate?
Further to the posts on thiocyanate leaching, it is possible to have silver thiocyanate in solution if the molarity of the thiocyanate solution is greater than 0.1 molar.
An example is ammonium thiocyanate which has a molecular weight of 76.
A 1 molar solution is approximately 76 g per litre, a 0.1 molar solution is approximately 7.6 g/l.
Thus if you have say 10 g/l of ammonium thiocyanate in solution you are safely over the minimum requirement for having silver thiocyanate in solution.
Keep in mind that if you are dissolving metals with such a solution you must remember that for the silver to stay in solution you must maintain the uncomplexed 10 g/l level of thiocyanate in solution.
This means that if you are carrying out a leach which will complex say 5 grams of thiocyanate with metals then you will need to start the leach with your 10 grams plus the extra 5 grams of thiocyanate in solution.
Think of the 10 g/l as just going along for the ride but not getting used.
The above applies for all thiocyanate leaching irrespective of whether the oxidant used is ferric salt at pH 1 to 2 or sulfuric acid at around 5% or other oxidants.
This means that if you are leaching material which contains both gold and silver you can dissolve both metals with the one leach.
The downside is that if metallic copper is present it too will stay in solution rather than form a passivating layer which prevents further complexation. This can use up your safety margin of thiocyanate fairly quickly and precipitation of copper and silver thiocyanate will occur.
Thiocyanate is cheap and non toxic so it is easy to use a leach solution with a large excess of thiocyanate if you do not know what the consumption of thiocyanate will be for a particular leach.
Deano
An example is ammonium thiocyanate which has a molecular weight of 76.
A 1 molar solution is approximately 76 g per litre, a 0.1 molar solution is approximately 7.6 g/l.
Thus if you have say 10 g/l of ammonium thiocyanate in solution you are safely over the minimum requirement for having silver thiocyanate in solution.
Keep in mind that if you are dissolving metals with such a solution you must remember that for the silver to stay in solution you must maintain the uncomplexed 10 g/l level of thiocyanate in solution.
This means that if you are carrying out a leach which will complex say 5 grams of thiocyanate with metals then you will need to start the leach with your 10 grams plus the extra 5 grams of thiocyanate in solution.
Think of the 10 g/l as just going along for the ride but not getting used.
The above applies for all thiocyanate leaching irrespective of whether the oxidant used is ferric salt at pH 1 to 2 or sulfuric acid at around 5% or other oxidants.
This means that if you are leaching material which contains both gold and silver you can dissolve both metals with the one leach.
The downside is that if metallic copper is present it too will stay in solution rather than form a passivating layer which prevents further complexation. This can use up your safety margin of thiocyanate fairly quickly and precipitation of copper and silver thiocyanate will occur.
Thiocyanate is cheap and non toxic so it is easy to use a leach solution with a large excess of thiocyanate if you do not know what the consumption of thiocyanate will be for a particular leach.
Deano
A
Anonymous
Guest
Deano
I've been reading this thread with interest and even more so the later developments regarding Thiocyanate leaching. Strangely enough it is both simple and cheap to get Ammonia Thiocyanate in the UK in liquid form but Sodium Thiocyanate is extremely expensive. I also note that Sodium Thiocyanate can be made using Ammonia Thiocyanate and Sodium Hydroxide. I'm no chemist so please correct me if I am wrong, but how simple would the process be?
I would also be extremely interesting in working out a process "end to end" as I get a lot of plated material and I have a hormonal aversion to cyanide leeching (i.e. I like to run away from it) and would like to see where this could be taken.
Assuming the success of deplating an item, what process would you recommend for precipitating?
Regards
Jon
I've been reading this thread with interest and even more so the later developments regarding Thiocyanate leaching. Strangely enough it is both simple and cheap to get Ammonia Thiocyanate in the UK in liquid form but Sodium Thiocyanate is extremely expensive. I also note that Sodium Thiocyanate can be made using Ammonia Thiocyanate and Sodium Hydroxide. I'm no chemist so please correct me if I am wrong, but how simple would the process be?
I would also be extremely interesting in working out a process "end to end" as I get a lot of plated material and I have a hormonal aversion to cyanide leeching (i.e. I like to run away from it) and would like to see where this could be taken.
Assuming the success of deplating an item, what process would you recommend for precipitating?
Regards
Jon
Jon
It makes no difference to the leaching if ammonium or sodium or potassium thiocyanate is used.
By using liquid ammonium form you get around the worry of keeping the thiocyanate, in whichever form you want to use, in a dry state.
The thiocyanate part is the important bit for forming metal complexes, the sodium or ammonium just goes along for the ride.
How you use this leach depends on what you are wanting to leach the precious metal from and what precious metals are present.
If you have the simplest combination of just gold plated on iron base ( this includes most forms of steel ) then run the leach at pH 1 to 2 using sulfuric or hydrochloric acid. Under these conditions the leach will need some iron in solution to act as an oxidiser before the gold will go into solution.
This leach form is very forgiving so there is no optimal iron level at which the leach must be run. Having less than theoretical iron levels just means that the leach is a bit slower, not that it will not work. Pretty well as long as you have iron colouring in the leach it will work.
Once some of the gold has been stripped the acid in the leach will start to attack the iron in the substrate. This will increase the iron level in the leach but will also raise the pH of the leach solution, this needs to be watched and more acid added if necessary. Keep in mind that generally 1% HCl solution will have a pH around 1 as will a 0.1% H2SO4 solution depending on what impurities are present in your water. This means that pH adjustment acid additions are usually very small, use a 1 to 5 ml disposable plastic pipette.
Hydrochloric acid will attack the iron much faster than sulfuric acid so if you are running large batches you want to use sulfuric acid so that you are not making a lot of iron complexes in your leach which you will have to deal with later. Also sulfuric acid is always readily available as battery acid at a cheaper price than hydrochloric acid.
I usually use around 5 grams of sodium thiocyanate per litre to ensure a reasonable leach rate. This gives a leach rate between cyanide and aqua regia. If you want it faster use more thiocyanate and dissolved iron.
If the gold is plated on a copper type base use a leach of maximum 5 g/l thiocyanate with just 5% sulfuric acid. Under these conditions the copper will form an insoluble copper thiocyanate layer which passivates the copper surface thus stopping acid attack on the copper.
If silver is also present in commercial quantities or at levels which will passivate the precious metal surface then you need to have the thiocyanate levels at 10 g/l of free sodium thiocyanate. Note that sodium and ammonium thiocyanate are interchangeable in this context.
This means that if you run this leach where the substrate is copper there will be no protective passivation of the copper when the precious metal layer is at least partly removed.
When using these leaches I always recover all dissolved metals with a carbon felt electrowin cell. No electrowin cell will strip all iron from a leach solution but if all other metals have been removed then bringing the residual solution to pH 7 will precipitate out the iron as an uncontaminated product which can be legally disposed of in landfill. The leftover solution of thiocyanate acts as a really good fertiliser. Thiocyanate is cheap enough that it is not worth trying to guess how much is left in the solution for re-use.
I dissolve the metals from the carbon felt in aqua regia and do a dibutyl ether recovery with oxalic acid finish if just gold is the precious metal I have leached.
If I have leached for low level silver as well as gold then I dissolve the metals from the carbon felt in aqua regia but adjust the liquor volume to keep all of the silver chloride in solution. An addition of pure table salt, not iodised, will cut down on the liquor volume needed. I adjust the pH to 1.5 with technical grade urea and precipitate the precious metals with sodium meta bisulfite.
Any contaminant metals in the residual aqua regia after the precipitation are removed by running it through another electrowin pass with the felt being reused multiple times until it is choked with base metals and it is then disposed of in an appropriate facility.
The above is easier than trying to play electrowinning games with voltages and current levels for clean precious metal recovery, it is not a system that is easy to control right through the process.
One obvious question is why do I use dibutyl ether instead of just a precipitation step when I have gold without silver.
It is cheaper to do the extraction method rather than the precipitation, the only chemical cost is the exchange of oxalic acid for gold.
You can drop metals directly from the leach solution with meta bisulfite but you will consume a lot of metabisulfite trying to knock out the iron in solution or the redox from the sulfuric acid. Way cheaper to do the electrowin step.
Deano
It makes no difference to the leaching if ammonium or sodium or potassium thiocyanate is used.
By using liquid ammonium form you get around the worry of keeping the thiocyanate, in whichever form you want to use, in a dry state.
The thiocyanate part is the important bit for forming metal complexes, the sodium or ammonium just goes along for the ride.
How you use this leach depends on what you are wanting to leach the precious metal from and what precious metals are present.
If you have the simplest combination of just gold plated on iron base ( this includes most forms of steel ) then run the leach at pH 1 to 2 using sulfuric or hydrochloric acid. Under these conditions the leach will need some iron in solution to act as an oxidiser before the gold will go into solution.
This leach form is very forgiving so there is no optimal iron level at which the leach must be run. Having less than theoretical iron levels just means that the leach is a bit slower, not that it will not work. Pretty well as long as you have iron colouring in the leach it will work.
Once some of the gold has been stripped the acid in the leach will start to attack the iron in the substrate. This will increase the iron level in the leach but will also raise the pH of the leach solution, this needs to be watched and more acid added if necessary. Keep in mind that generally 1% HCl solution will have a pH around 1 as will a 0.1% H2SO4 solution depending on what impurities are present in your water. This means that pH adjustment acid additions are usually very small, use a 1 to 5 ml disposable plastic pipette.
Hydrochloric acid will attack the iron much faster than sulfuric acid so if you are running large batches you want to use sulfuric acid so that you are not making a lot of iron complexes in your leach which you will have to deal with later. Also sulfuric acid is always readily available as battery acid at a cheaper price than hydrochloric acid.
I usually use around 5 grams of sodium thiocyanate per litre to ensure a reasonable leach rate. This gives a leach rate between cyanide and aqua regia. If you want it faster use more thiocyanate and dissolved iron.
If the gold is plated on a copper type base use a leach of maximum 5 g/l thiocyanate with just 5% sulfuric acid. Under these conditions the copper will form an insoluble copper thiocyanate layer which passivates the copper surface thus stopping acid attack on the copper.
If silver is also present in commercial quantities or at levels which will passivate the precious metal surface then you need to have the thiocyanate levels at 10 g/l of free sodium thiocyanate. Note that sodium and ammonium thiocyanate are interchangeable in this context.
This means that if you run this leach where the substrate is copper there will be no protective passivation of the copper when the precious metal layer is at least partly removed.
When using these leaches I always recover all dissolved metals with a carbon felt electrowin cell. No electrowin cell will strip all iron from a leach solution but if all other metals have been removed then bringing the residual solution to pH 7 will precipitate out the iron as an uncontaminated product which can be legally disposed of in landfill. The leftover solution of thiocyanate acts as a really good fertiliser. Thiocyanate is cheap enough that it is not worth trying to guess how much is left in the solution for re-use.
I dissolve the metals from the carbon felt in aqua regia and do a dibutyl ether recovery with oxalic acid finish if just gold is the precious metal I have leached.
If I have leached for low level silver as well as gold then I dissolve the metals from the carbon felt in aqua regia but adjust the liquor volume to keep all of the silver chloride in solution. An addition of pure table salt, not iodised, will cut down on the liquor volume needed. I adjust the pH to 1.5 with technical grade urea and precipitate the precious metals with sodium meta bisulfite.
Any contaminant metals in the residual aqua regia after the precipitation are removed by running it through another electrowin pass with the felt being reused multiple times until it is choked with base metals and it is then disposed of in an appropriate facility.
The above is easier than trying to play electrowinning games with voltages and current levels for clean precious metal recovery, it is not a system that is easy to control right through the process.
One obvious question is why do I use dibutyl ether instead of just a precipitation step when I have gold without silver.
It is cheaper to do the extraction method rather than the precipitation, the only chemical cost is the exchange of oxalic acid for gold.
You can drop metals directly from the leach solution with meta bisulfite but you will consume a lot of metabisulfite trying to knock out the iron in solution or the redox from the sulfuric acid. Way cheaper to do the electrowin step.
Deano
Will this leach any of the pgms?
A
Anonymous
Guest
Hi Deano
For reference my base material tends to be IT equipment, so gold plating tends to be copper based with a nickel layer between. There are some items which have gold direct onto copper and these tend to be heavier units and since you mentioned the passivation of the copper base within this process I think it certainly deserves some research. There is no iron at all in the product I will be processing, once prepared correctly.
Also most of the material has either silver or gold so there is very very little crossover.
As such this method could be an extremely practical alternative. Thank you.
Also Ammonium Thiocyanate is sold in the UK in 2.5l bottles at a concentration of 0.1M. Is that suitable?
For reference my base material tends to be IT equipment, so gold plating tends to be copper based with a nickel layer between. There are some items which have gold direct onto copper and these tend to be heavier units and since you mentioned the passivation of the copper base within this process I think it certainly deserves some research. There is no iron at all in the product I will be processing, once prepared correctly.
Also most of the material has either silver or gold so there is very very little crossover.
As such this method could be an extremely practical alternative. Thank you.
Also Ammonium Thiocyanate is sold in the UK in 2.5l bottles at a concentration of 0.1M. Is that suitable?
The only reference I can find to leaching of PGMs with thiocyanate says that only palladium is leached by thiocyanate at room temperature. No reference is made to leach conditions apart from the temperature.
According to the literature nickel thiocyanate can only be formed as a reaction between salts in solution. If this is correct then there should be no attack on the nickel layer by a thiocyanate leach assuming that the reagents in the leach apart from the thiocyanate do not strongly attack the nickel. I cannot find any data for solubility of nickel thiocyanate in water.
0.1M ammonium thiocyanate solution is right on the cusp of silver solubility. Think of it as around 7.6 g/l solution.
If you were to dilute it to 5g/l the solution will not dissolve silver but will just take up gold.
If you want to dissolve silver then you will want to raise the level of the ammonium thiocyanate so that you always have 10 g/l ammonium in solution after dissolving the silver.
You can increase the ammonium thiocyanate level in solution by boiling off some of the water from your solution. Keep in mind that ammonium thiocyanate is only stable up to 170C, so keep your heat source on low or use a water bath and accept the extra time involved.
Deano
According to the literature nickel thiocyanate can only be formed as a reaction between salts in solution. If this is correct then there should be no attack on the nickel layer by a thiocyanate leach assuming that the reagents in the leach apart from the thiocyanate do not strongly attack the nickel. I cannot find any data for solubility of nickel thiocyanate in water.
0.1M ammonium thiocyanate solution is right on the cusp of silver solubility. Think of it as around 7.6 g/l solution.
If you were to dilute it to 5g/l the solution will not dissolve silver but will just take up gold.
If you want to dissolve silver then you will want to raise the level of the ammonium thiocyanate so that you always have 10 g/l ammonium in solution after dissolving the silver.
You can increase the ammonium thiocyanate level in solution by boiling off some of the water from your solution. Keep in mind that ammonium thiocyanate is only stable up to 170C, so keep your heat source on low or use a water bath and accept the extra time involved.
Deano
Hullo there Deano,
Thank-you for your very interesting information.
Do you know if the thiocyanate leach is as selective as the thiourea leach as I have ore that is 30% Antimony (as stibnite), chalcopyrite, arsenopyrite and better than 5oz gold and 10oz silver per ton.
My idea is to crush the ore using a jaw crusher and ball mill and then float off the stibnite using flotation tanks and then put the remains left in the bottom of the tanks over a vibration table to separate and treat the free gold and silver and then roast the sulphides to release their values using a suitable leach.
I understand that the antimony will interfere and destroy most luxivants, but thiourea is not effected by this effect.
I was planning to use thiourea but I also understand that there is problems with finding a precipitant that is reasonably well priced and easily available.
Cheers Mate,
Allan.
Thank-you for your very interesting information.
Do you know if the thiocyanate leach is as selective as the thiourea leach as I have ore that is 30% Antimony (as stibnite), chalcopyrite, arsenopyrite and better than 5oz gold and 10oz silver per ton.
My idea is to crush the ore using a jaw crusher and ball mill and then float off the stibnite using flotation tanks and then put the remains left in the bottom of the tanks over a vibration table to separate and treat the free gold and silver and then roast the sulphides to release their values using a suitable leach.
I understand that the antimony will interfere and destroy most luxivants, but thiourea is not effected by this effect.
I was planning to use thiourea but I also understand that there is problems with finding a precipitant that is reasonably well priced and easily available.
Cheers Mate,
Allan.
Generally you are going to float all the sulfides at once along with any free gold, you might want to reconsider your flowsheet.
Thiourea is not used much because gold thiourea complexes are not easily concentrated on an adsorbent medium such as activated carbon. This means that you are restricted to either direct electrowinning from the leach solution and the related destruction of the thiourea or chemical precipitation from the leach solution.
Both of the above involve a filtration stage.
Personally I don't use thiourea because it is a known carcinogen.
That said, if the thiourea leach is totally kept away from UV then it is a very good leach for use with stibnite.
Personally I would look at doing a bulk float and selling the float cons or having them toll treated at a smelter. You can then test the float tails to see if they are worth further treatment.
I have no information on the use of thiocyanate with stibnite.
Deano
Thiourea is not used much because gold thiourea complexes are not easily concentrated on an adsorbent medium such as activated carbon. This means that you are restricted to either direct electrowinning from the leach solution and the related destruction of the thiourea or chemical precipitation from the leach solution.
Both of the above involve a filtration stage.
Personally I don't use thiourea because it is a known carcinogen.
That said, if the thiourea leach is totally kept away from UV then it is a very good leach for use with stibnite.
Personally I would look at doing a bulk float and selling the float cons or having them toll treated at a smelter. You can then test the float tails to see if they are worth further treatment.
I have no information on the use of thiocyanate with stibnite.
Deano
kurtak
Well-known member
Deano
Good to hear from you again - its been a couple months since you last posted - I enjoy reading the info you post here
Kurt
Good to hear from you again - its been a couple months since you last posted - I enjoy reading the info you post here
Kurt
Just saw this thread.
Brilliant info thanks Deano.
sprigsie
It was interesting to me that you mention thiourea and that it was carcinogenic because it is in Goodards Silver dip available in the UK. It was the only thing that removed the silver nitrate stains from my worktop which had been there for about six months when I started silver refining. I tried everthing else I had, to remove those stains. Thought they would be there for ever.
Brilliant info thanks Deano.
sprigsie
It was interesting to me that you mention thiourea and that it was carcinogenic because it is in Goodards Silver dip available in the UK. It was the only thing that removed the silver nitrate stains from my worktop which had been there for about six months when I started silver refining. I tried everthing else I had, to remove those stains. Thought they would be there for ever.
Hullo there Eamonn,
Yes, that's correct that theourea is a known carcinogen, but I don't know just at what concentrations that it is actually carcinogenic because currently the main use for theourea is in municipal city water supplies throughout the world to clarify the water, so I ask, is this chemical really that dangerous.
Cheers Mate,
Allan.
Yes, that's correct that theourea is a known carcinogen, but I don't know just at what concentrations that it is actually carcinogenic because currently the main use for theourea is in municipal city water supplies throughout the world to clarify the water, so I ask, is this chemical really that dangerous.
Cheers Mate,
Allan.
necromancer
Well-known member
Deano said:
this is the only worthy document i can find about "thiourea in our water" in canada.
it says nothing about it being used in any "municipal fresh water supplies" only as a environmental toxin from Industry.
Source: (Environment Canada) see section (5.1)
PDF version
http://www.ec.gc.ca/ese-ees/EC008C1F-D726-423A-B1E4-07B00BAD338C/batch2_62-56-6_rm_en.pdf
Further to the previous thiocyanate testwork I was interested in the recovery of gold thiocyanate from leach solution.
There is a lot of literature which says that gold thiocyanate will load onto activated carbon from a pulp. There is not a lot of literature which compares the loading rates and levels of gold thiocyanate onto carbon with gold cyanide or gold chloride.
I ran three liquors with the same gold tenor of 1ppm gold as a chloride at pH 2 (pH adjusted with HCl), gold as a cyanide at pH 11 (500 ppm cyanide in solution), gold as a thiocyanate at pH 2 (5 grams per litre thiocyanate and 5 grams per litre iron as ferric chloride).
Each liquor was contacted with activated carbon at the same rate of 5 grams per litre carbon in liquor.
After 1 hour the gold levels in the liquors were chloride 0.21ppm, cyanide 0.32ppm, thiocyanate 0.06ppm.
After 2hours the gold levels in the liquors were chloride 0.11ppm, cyanide 0.16ppm, thiocyanate 0.01ppm.
After 3 hours the gold levels in the liquors were chloride 0.07ppm, cyanide 0.12ppm, thiocyanate 0.00ppm.
After 3 hours the carbons were removed from the liquors and dried at 90C overnight.
The dried carbons were then ashed in open top ceramic dishes in an electric furnace at 600C.
The ash was digested in aqua regia and the recovered gold was calculated from AAS analysis.
For gold chloride 93 micrograms of gold loaded onto activated carbon returned 91.3 micrograms
For gold cyanide 88 micrograms of gold loaded onto activated carbon returned 86.5 micrograms.
For gold thiocyanate 100 micrograms of gold loaded onto activated carbon returned 98.6 micrograms.
Effectively the three types of gold complexes recovered similar similar percentages of gold from carbon within the accuracy of the analyses.
It should be noted that the gold thiocyanate loaded faster and more completely than the gold chloride or gold cyanide under the conditions described.
The above indicates that activated carbon is a suitable adsorbent for gold thiocyanate complexes at pH 2 where iron is used as an oxidant.
Deano
There is a lot of literature which says that gold thiocyanate will load onto activated carbon from a pulp. There is not a lot of literature which compares the loading rates and levels of gold thiocyanate onto carbon with gold cyanide or gold chloride.
I ran three liquors with the same gold tenor of 1ppm gold as a chloride at pH 2 (pH adjusted with HCl), gold as a cyanide at pH 11 (500 ppm cyanide in solution), gold as a thiocyanate at pH 2 (5 grams per litre thiocyanate and 5 grams per litre iron as ferric chloride).
Each liquor was contacted with activated carbon at the same rate of 5 grams per litre carbon in liquor.
After 1 hour the gold levels in the liquors were chloride 0.21ppm, cyanide 0.32ppm, thiocyanate 0.06ppm.
After 2hours the gold levels in the liquors were chloride 0.11ppm, cyanide 0.16ppm, thiocyanate 0.01ppm.
After 3 hours the gold levels in the liquors were chloride 0.07ppm, cyanide 0.12ppm, thiocyanate 0.00ppm.
After 3 hours the carbons were removed from the liquors and dried at 90C overnight.
The dried carbons were then ashed in open top ceramic dishes in an electric furnace at 600C.
The ash was digested in aqua regia and the recovered gold was calculated from AAS analysis.
For gold chloride 93 micrograms of gold loaded onto activated carbon returned 91.3 micrograms
For gold cyanide 88 micrograms of gold loaded onto activated carbon returned 86.5 micrograms.
For gold thiocyanate 100 micrograms of gold loaded onto activated carbon returned 98.6 micrograms.
Effectively the three types of gold complexes recovered similar similar percentages of gold from carbon within the accuracy of the analyses.
It should be noted that the gold thiocyanate loaded faster and more completely than the gold chloride or gold cyanide under the conditions described.
The above indicates that activated carbon is a suitable adsorbent for gold thiocyanate complexes at pH 2 where iron is used as an oxidant.
Deano
Always appreciate such a study, and I compliment you on you your work--always good stuff from you. Seems like the recoveries by AA might mean even better news. Sometimes AA runs low.
You should test a poly acrylic ester resin for gold sorptiin. XAD-7 (Dow) is supposed to be good. Gold loves esters/ethers/ketones. Imagine if it took gold out of reverse aqua regia. I theorize it should. Reckon it elutes with water. Should be oxidatively stable.
You should test a poly acrylic ester resin for gold sorptiin. XAD-7 (Dow) is supposed to be good. Gold loves esters/ethers/ketones. Imagine if it took gold out of reverse aqua regia. I theorize it should. Reckon it elutes with water. Should be oxidatively stable.
solar_plasma
Well-known member
This thread should be copied to the library. Informatively and captivating, understandible to us kinda laypeople, it shows the beauty of scientific work.
