Some Nitric Acid Questions

[jeff@performance-construc]

Hi there, hoping I can get some help with these questions:

1. What is a simple tried-and-true method to neutralize bulk dilute nitric acid solutions?
2. Is it possible to neutralize spent silver electrolyte solution before recovering the silver with via cementation?
3. Is there any type of test equipment made that can easily assay nitric acid solutions?

Thanks in advance for any help or thoughts on this.

Jeff

 

[Yggdrasil]

Hi there, hoping I can get some help with these questions:

1. What is a simple tried-and-true method to neutralize bulk dilute nitric acid solutions?
2. Is it possible to neutralize spent silver electrolyte solution before recovering the silver with via cementation?
3. Is there any type of test equipment made that can easily assay nitric acid solutions?

Thanks in advance for any help or thoughts on this.

Jeff

1. Easy to neutralize any acid, just add a caustic salt/Solution until the pH is 7.
Why do you want to neutralize it is another matter, is it waste treatment?
2. No keep the solution acidic so the cementation works.
3. Spectrographs will do that, but there are chemical means too like titrations.
What is the purpose?

 

[jeff@performance-construc]

Yggdrasil,

Thank you for replaying back to me I appreciate it very much.

So, we are looking for a safe cost-effective way to neutralize used nitric based electrolytic solution 90 liters every 24 hrs. for processing in our Metals Recovery system and the on to our resin tanks for filtration to distilled water. We have been using the mainstream caustic salt/Solutions and it's not as easy or clean as one would think especially at a larger volume. We were hoping to find a possible manufactured premixed liquid solution to use in the neutralization process.

We have tested cementing out silver with neutralized solutions and have had mixed results. The reason we are interested in assaying our nitric acid solutions is to learn all we can about the consumption of and strengths of nitric acid versus the yields on silver during the refining process.

So, our end goal here and we have been working on this for several years is to refine and mint silver without the use of any heat whatsoever and so far, we have met that goal. Our biggest challenge right now is to figure out better way to neutralize our used solutions.

Again, thank you.

Jeff

PS: I am attaching some photos of our R&D work

 

[Yggdrasil]

Yggdrasil,

Thank you for replaying back to me I appreciate it very much.

So, we are looking for a safe cost-effective way to neutralize used nitric based electrolytic solution 90 liters every 24 hrs. for processing in our Metals Recovery system and the on to our resin tanks for filtration to distilled water. We have been using the mainstream caustic salt/Solutions and it's not as easy or clean as one would think especially at a larger volume. We were hoping to find a possible manufactured premixed liquid solution to use in the neutralization process.

We have tested cementing out silver with neutralized solutions and have had mixed results. The reason we are interested in assaying our nitric acid solutions is to learn all we can about the consumption of and strengths of nitric acid versus the yields on silver during the refining process.

So, our end goal here and we have been working on this for several years is to refine and mint silver without the use of any heat whatsoever and so far, we have met that goal. Our biggest challenge right now is to figure out better way to neutralize our used solutions.

Again, thank you.

Jeff

PS: I am attaching some photos of our R&D work

I believe cementing should be done while still acidic.
If the solution is neutral there are nothing to drive the ion exchange to completion.

 

[Yggdrasil]

Yggdrasil,

Thank you for replaying back to me I appreciate it very much.

So, we are looking for a safe cost-effective way to neutralize used nitric based electrolytic solution 90 liters every 24 hrs. for processing in our Metals Recovery system and the on to our resin tanks for filtration to distilled water. We have been using the mainstream caustic salt/Solutions and it's not as easy or clean as one would think especially at a larger volume. We were hoping to find a possible manufactured premixed liquid solution to use in the neutralization process.

We have tested cementing out silver with neutralized solutions and have had mixed results. The reason we are interested in assaying our nitric acid solutions is to learn all we can about the consumption of and strengths of nitric acid versus the yields on silver during the refining process.

So, our end goal here and we have been working on this for several years is to refine and mint silver without the use of any heat whatsoever and so far, we have met that goal. Our biggest challenge right now is to figure out better way to neutralize our used solutions.

Again, thank you.

Jeff

PS: I am attaching some photos of our R&D work

Here is a snippet from "Finishing dot com"

An old fashioned way is 10 ml of solution in 100 ml distilled water, a couple of drops of methyl orange indicator,
titrated with 1N NaOH from a red to a yellow orange end point.
Titrate slowly so you do not get a false reading from dissolved metals that precipitate out as hydroxides.

 

[cejohnsonsr1]

I would have to think that the best way to “neutralize” nitric acid would be to add more silver until it is all consumed. If you’re processing silver in an electrolytic cell, you must be using a feedstock. Is that feedstock not being processed to remove base metals and recover the silver prior to running through the cell? If so, you’re most likely dissolving it the same way you dissolve more pure silver for electrolyte. Just take your spent electrolyte and put it right back into the process at an earlier point. Saturation of silver nitrate with copper and other base metals is much lower as an electrolyte than as a primary solution in the recovery stage. After cementation (or whatever precipitation method you use) the remaining copper nitrate can be cemented onto iron and then neutralized much easier. This method of waste management has the benefit of being more efficient by consuming rather than neutralizing nitric acid and producing less waste which is easier to process. It also produces metallic copper as a byproduct which can be sold.

 

[BGDOCK]

just throwing this out :

If instead of cementation you make silver chloride . Then when using the sugar/ lye method couldn’t you use the lye and washings to bring the ph to 7 ? It’s early and no coffee yet for the record . I use my spent lye solutions in the last couple of stages of waste treatment . That is a great setup by the way .

 

[andu]

If you cementing silver I assume with copper can't you just use all the nitric up on copper? You can even recover some nitric if you wanna bother with it.

 

[jeff@performance-construc]

We are kind of doing just that, but we have to rush the cementing process to reduce the amount of copper that gets dissolved into the solutions. We are using rotating 6" tubes that hang down into a 30-gallon tank. Once we recover the silver, we then neutralize the used nitric solution with Sodium Bicarbonate on a 1 to 1 ratio. We have to do this before we can process the liquids through filtration. This the part of the refining process that I dislike the most lol

 

[cejohnsonsr1]

just throwing this out :

If instead of cementation you make silver chloride . Then when using the sugar/ lye method couldn’t you use the lye and washings to bring the ph to 7 ? It’s early and no coffee yet for the record . I use my spent lye solutions in the last couple of stages of waste treatment . That is a great setup by the way .

Without a really good reason, like some contaminant that can’t be gotten rid of any other way, using the lye and sugar method just adds 3 steps to the process and produces significantly more waste that has to be treated, just to wind up with the same mud you get from cementing on copper.

 

[andu]

We are kind of doing just that, but we have to rush the cementing process to reduce the amount of copper that gets dissolved into the solutions. We are using rotating 6" tubes that hang down into a 30-gallon tank. Once we recover the silver, we then neutralize the used nitric solution with Sodium Bicarbonate on a 1 to 1 ratio. We have to do this before we can process the liquids through filtration. This the part of the refining process that I dislike the most lol

If you let it settle you should be able to siphon most the solution without filtering. Heat always seems a good idea, I like to take advantage of the sun for example, I understand why you'd avoid heat. I now assume the solution is not aireated.

Why you mind the copper going into solution as long as it doesn't contaminate your silver? Pardon me here but i'm a novice, I know a small amount of it tends to go with the cemented metal but it's usually minimal and would get rid in electrolysis.

Can't one nearly completely neutralize nitric with the copper?

 

[cejohnsonsr1]

If you let it settle you should be able to siphon most the solution without filtering. Heat always seems a good idea, I like to take advantage of the sun for example, I understand why you'd avoid heat. I now assume the solution is not aireated.

Why you mind the copper going into solution as long as it doesn't contaminate your silver? Pardon me here but i'm a novice, I know a small amount of it tends to go with the cemented metal but it's usually minimal and would get rid in electrolysis.

Can't one nearly completely neutralize nitric with the copper?

Copper doesn’t really neutralize nitric acid. It consumes it.

 

[BGDOCK]

Oops posted I. Wrong place

 

[BGDOCK]

If you let it settle you should be able to siphon most the solution without filtering. Heat always seems a good idea, I like to take advantage of the sun for example, I understand why you'd avoid heat. I now assume the solution is not aireated.

Why you mind the copper going into solution as long as it doesn't contaminate your silver? Pardon me here but i'm a novice, I know a small amount of it tends to go with the cemented metal but it's usually minimal and would get rid in electrolysis.

Can't one nearly completely neutralize nitric with the copper?

That may be but isn’t there less copper in the silver when performing L/S method vs Cementation, if the quality is better that would be a good reason . However time is money so perhaps .995-.997 is ok . I personally think L/S gives better looking silver.

 

[BGDOCK]

Posted in wrong place again I was trying to respond to cejohnson reply . I’m done good night jeez

 

[andu]

Copper doesn’t really neutralize nitric acid. It consumes it.

That's precisely my point, you can recover the nitric atleast partly if you care, and get rid of maybe most acidity.

 

[cejohnsonsr1]

That may be but isn’t there less copper in the silver when performing L/S method vs Cementation, if the quality is better that would be a good reason . However time is money so perhaps .995-.997 is ok . I personally think L/S gives better looking silver.

No. There’s no less copper in one process than the other. The starting solution is silver nitrate and copper nitrate. Whether you cement on copper or convert to silver chloride, all of the copper nitrate is still present and mixed just as thoroughly with the silver. You still have to rinse the silver chloride the same as you would the cement silver and, like the cement silver, you’ll never get it all out. The difference is that when you’re done rinsing you have to make 2 more conversions that require additional rinsing to remove the lye and sugar but leave exactly as much copper as it already contained. And when you arrive at that point you’ve got exactly what you would have had if you had just cemented on copper. But you will have spent more time and money on 3 extra steps and produced significantly more waste which has to be treated.

 

[kurtak]

No. There’s no less copper in one process than the other. The starting solution is silver nitrate and copper nitrate. Whether you cement on copper or convert to silver chloride, all of the copper nitrate is still present and mixed just as thoroughly with the silver. You still have to rinse the silver chloride the same as you would the cement silver and, like the cement silver, you’ll never get it all out. The difference is that when you’re done rinsing you have to make 2 more conversions that require additional rinsing to remove the lye and sugar but leave exactly as much copper as it already contained. And when you arrive at that point you’ve got exactly what you would have had if you had just cemented on copper. But you will have spent more time and money on 3 extra steps and produced significantly more waste which has to be treated.

This is mis- information (not true information)

If you want to know why this is mis-information read what I have posted in this thread -----

https://goldrefiningforum.com/threads/converting-925-scrap-silver-to-shot-for-my-anode-basket.33490/

 

[snoman701]

We have to do this before we can process the liquids through filtration. This the part of the refining process that I dislike the most lol

Same my friend, same!

For your desilvered solution.

Quit using sodium bicarb. You want to use sodium hydroxide or potassium hydroxide. In bag quantity it's pretty inexpensive. I think I was paying $2/lb or so. Make a stock solution of the caustic and utilize it to raise your pH of your electrolyte to around 10 as slowly as possible with a lot of stirring action. For the quantities you are doing, you want to do this with a mechanical stirrer. Now you have choices in how to handle your slurry. You can use a filter press for ease, but they are expensive. You can also give it 24 hours to settle out, decant off the liquid then pour the sludgy material into a vacuum filter. Dry the copper hydroxides and batch them. I'd say they are a sellable product, but they may not be as you do not have any gold in them. The liquid, you will need to add enough sulfuric acid to to bring the pH back down to 6. At this point, legally, you should batch it into 250 gallon totes and pay to have it disposed of. Before you do that, you need to get it checked via ICP to make sure it's dissolved metal free. It should be.

There's of course a lot more legal requirements to doing this in the US.

 

[4metals]

I missed this thread, it is actually more details of the other thread the OP started describing his unique bowl cells.

but we have to rush the cementing process to reduce the amount of copper that gets dissolved into the solutions. We are using rotating 6" tubes that hang down into a 30-gallon tank.

I assume that the reason you want to reduce the copper that gets dissolved into solution is because those 6" diameter copper tubes you rotate in the solution are pricey and you don't want them to dissolve too quickly. I do not understand why you rotate the tubes, is there some sort of scraper that dislodges the cemented Silver from the rotating cylinder? I usually aerate a cylinder that copper slabs hang inside of inside the tank of liquid to be cemented to guarantee circulation and allow the aeration to dislodge the Silver. One thing I would look out for if you have concerns for dissolving too much copper is the free nitric acid that may be in your solution before you start the process. Since you will be dropping the Silver out as a cement anyway, one easy method would be to add some cement Silver you have from previous lots and mix it well. Not a lot, a few ounces should suffice. If there is substantial free nitric you will see the red cloud which the Silver will generate as it consumes the free nitric on it's path to becoming Silver Nitrate. If there is no free nitric, or if there is some added Silver remaining, no issue because you will be cementing the Silver now in solution into the same vessel so there will be no lost Silver and no excessive consumption of Copper

I never worry about too much copper dissolving because once the cementing is done, the electrolyte is treated with sodium hydroxide to raise the pH and drop the copper as copper hydroxide. Copper starts coming out of solution at a pH of 6 and it is done dropping at a pH of 8. This method drops the copper remaining in solution into the fractional PPM range. At a pH of 8 the solution may or may not be right for your resin to be effective but you can neutralize easily with sulfuric acid. The down side to this method is the remaining solution is a very briny solution.

The resulting copper hydroxide sludge will settle and the thick sludge can be de-watered in a typical filtration funnel but it is very slow, a filter press is the best bet but for around 25 gallons per day a vacuum filter may work. Once the bulk of the hydroxides settle, the liquid on top can be siphoned off to go through your resin process. The solid material is saleable to copper smelters.

Below is a chart showing different metals and what pH they drop out at. Notice some metals, lead and zinc in particular go back into solution if the pH goes too high. Notice that Silver doesn't actually start to drop until you are at a pH of 10.