Aluminum Nitrate Disposal??

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rybak97

Well-known member
Joined
Mar 14, 2013
Messages
69
Aluminum Nitrate Disposal
I’ve been silver refining for quite a while and have found myself with around 40 gals silver refining byproduct I need to safely dispose of. Once all my silver has dropped out of solution I use large pieces of aluminum to drop out the copper.

After a while the liquid turns nearly clear letting me know the majority of copper has been removed. I then dump the resulting solution in a large drum and now here I am.

My questions is what is the safest way to dispose of this byproduct? I’ve read aluminum nitrate is quit reactive so dumping it down the drain I assume is out of the questions. I want to make sure it’s done properly.
Any procedures to neutralize would be appreciated.
 
The addition of NaOH to your nitrate will yield aluminum hydroxide which is insoluble.

Al(NO3)3 + 3 NaOH → Al(OH)3 + 3 NaNO3
 
Add caustic to the aluminum solution to raise the pH to 7.2 at which point AlOH3 will drop out of solution.

Unfortunately, Aluminum Hydroxide is a gelatinous precipitate so it may be difficult to filter, settling would be the better option.
 
Once neutralised as per 4metals instructions you could try wicking the spent solution as described by GSP.
 
4metals said:
Add caustic to the aluminum solution to raise the pH to 7.2 at which point AlOH3 will drop out of solution.

Unfortunately, Aluminum Hydroxide is a gelatinous precipitate so it may be difficult to filter, settling would be the better option.

So once the AlOH3 has dropped out the remaining liquid can be disposed of down the drain? What about the gelatinous precipitate? Do I just throw it away?
 
Every municipality has different discharge limits so that is a difficult question to answer.

The aluminum will have knocked down all of the metals under it on the electromotive series and the caustic will drop the aluminum BUT, depending on a lot of variables it is possible for you to leave behind a few parts per million of some other metals which may or may not exceed your local discharge limits. I can say that I do have clients who used the same procedure and had the waste tested and it did meet standards for discharge. But to categorically say that is the case for your waste would be speculation. You could neutralize the water and put it in a solar still and evaporate it. If you generated 40 gallons over how much time? Solar evaporation may be capable of keeping up with your production.

You can dry the sludge and calcine it to make it into alumina (Aluminum Oxide) which can go to a landfill.
 
Listen to 4metals advice, if anyone can tell you the rules and procedures to follow its him,in the bad old days the acids were dumped into the system and got who knows where along with many heavy metals, it could end up back in your drinking water many days, months or years later. Now we have to be seen whiter than white as we are under scutiny from many government agencies let alone the moral responsibility to do the right thing.
If you are not sure check your local regulations and abide by them, need more help ask, I'm sure we are all too happy to help.
 
4metals said:
Add caustic to the aluminum solution to raise the pH to 7.2 at which point AlOH3 will drop out of solution.
Which is exactly what will happen if you're Dealing with Waste using a treatment system similar to what 4metals has laid out previously (see linked thread).

I use iron instead of aluminum, but the process is essentially the same: Use a more reactive metal to drop the copper out, then raise the pH to drop remaining metal content. Lower the pH again if necessary to neutralize your remaining solution. Properly dispose of your remaining solids and neutralized solution.
 
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