SunSilver1993
New member
- Joined
- Jun 12, 2024
- Messages
- 4
Hi All,
I have a silicon powder from crushed up solar panels that I am trying to determine the silver content of. The powder contains Silicon, Copper, Aluminium Iron and Tin. We already have an XRF analysis showing that it contains 0.4wt% silver.
I would like to confirm this result via chemical assay. This would also have the added benefit of having a way to test silver in house without XRF.
On that matter I've already tried a couple of things and am looking for some advice. In short, I've tried the silver chloride method a couple of times and tried once to plate silver out onto copper but need advice on both. I am also wondering if there is a relatively simple titration I could perform to determine silver content of the solution without having to isolate the powder (something like reverse argentrometry?)
Silver Chloride method
I've added silicon powder to excess 30% Nitric acid and heated under stirring until evolution of NO2 stopped. I then filtered the solution and rinsed the powder to collect a clear blue solution to which I added excess NaCl. This caused a colour change to lime green and the formation of a very fine precipitate.
Attempts to filter this solution and collect the insolubles resulted in no collected powder and a milky solution in the buchner flask below. It appears that the precipitate is so fine that it can't be filtered?
Is there anything I'm missing here? Should I be adjusting the pH prior to adding NaCl?
Silver Plating
I followed the same procedure to collect the clear blue solution above. I then attempted to neutralise this with a concentrated NaOH solution. The reason I did this is that I wanted to take the pH to a point where the nitric didn't react with the copper so the plating would be obvious to observe and easier to collect for weighing. Addition of NaOH caused the temporary formation of a black precipitate which would go back into solution. I kept adding NaOH at this point hoping to stop the formation of the precipitate but pushed it too far and a permanent precipitate formed . At this point I was discouraged so I discarded the solution.
So for this experiment I have the questions;
- What pH should I neutralise to ? I don't have an easy way of testing pH so would rather just add a fixed amount of NaOH or bicarb
- Should I use sodium bicarbonate instead?
- Should I just keep adding copper that will dissolve until silver starts to plate out on it? Seems quite wasteful and generates a lot of soluble copper which obviously isn't ideal from a disposal point of view.
- What is that black precipitate?
- Will this method be an accurate way to determine silver content once I've collected the silver?
Titration
Looking for any suggestions here, anyone have any experience with this? The more I think about it the better of an idea this seems as there will be no losses from filtering and likely I can use a much smaller sample.
Thank you so much in advance for any help
I have a silicon powder from crushed up solar panels that I am trying to determine the silver content of. The powder contains Silicon, Copper, Aluminium Iron and Tin. We already have an XRF analysis showing that it contains 0.4wt% silver.
I would like to confirm this result via chemical assay. This would also have the added benefit of having a way to test silver in house without XRF.
On that matter I've already tried a couple of things and am looking for some advice. In short, I've tried the silver chloride method a couple of times and tried once to plate silver out onto copper but need advice on both. I am also wondering if there is a relatively simple titration I could perform to determine silver content of the solution without having to isolate the powder (something like reverse argentrometry?)
Silver Chloride method
I've added silicon powder to excess 30% Nitric acid and heated under stirring until evolution of NO2 stopped. I then filtered the solution and rinsed the powder to collect a clear blue solution to which I added excess NaCl. This caused a colour change to lime green and the formation of a very fine precipitate.
Attempts to filter this solution and collect the insolubles resulted in no collected powder and a milky solution in the buchner flask below. It appears that the precipitate is so fine that it can't be filtered?
Is there anything I'm missing here? Should I be adjusting the pH prior to adding NaCl?
Silver Plating
I followed the same procedure to collect the clear blue solution above. I then attempted to neutralise this with a concentrated NaOH solution. The reason I did this is that I wanted to take the pH to a point where the nitric didn't react with the copper so the plating would be obvious to observe and easier to collect for weighing. Addition of NaOH caused the temporary formation of a black precipitate which would go back into solution. I kept adding NaOH at this point hoping to stop the formation of the precipitate but pushed it too far and a permanent precipitate formed . At this point I was discouraged so I discarded the solution.
So for this experiment I have the questions;
- What pH should I neutralise to ? I don't have an easy way of testing pH so would rather just add a fixed amount of NaOH or bicarb
- Should I use sodium bicarbonate instead?
- Should I just keep adding copper that will dissolve until silver starts to plate out on it? Seems quite wasteful and generates a lot of soluble copper which obviously isn't ideal from a disposal point of view.
- What is that black precipitate?
- Will this method be an accurate way to determine silver content once I've collected the silver?
Titration
Looking for any suggestions here, anyone have any experience with this? The more I think about it the better of an idea this seems as there will be no losses from filtering and likely I can use a much smaller sample.
Thank you so much in advance for any help