Ferric Chloride Disposal

I have in a small container "used ferric chloride with copper", which now I am trying to dispose.

Based on the information from the web I decided to use Sodium Carbonate or Sodium Hydroxide to first neutralize. I bought Sodium hydroxide and tried to add this to my used etchant... Nothing happened.
I added two table spoons . I got this as NAOH crystals and added "as is". Do I need to powder it before adding or any one can specify a quantity? Also now if I add sodium carbonate over the already added naoh will it be a problem (or could fix the issue) ?

Forgot to tell one thing. When I took this back after this, the container bottom was hot..

It will be nice if someone could give a link or so for a video demo of this. (could be great).

In my website I have an article on this ... **broken link removed**
Check the "Etching with Ferric Chloride" section
I used Sodium Carbonate ...

Forgot to tell one thing. When I took this back after this, the container bottom was hot..

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Its normal its an exothermic reaction so it will produce heat...

Good Luck

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Do I need to powder it before adding

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Not needed but doing so can increase the reaction a bit..

any one can specify a quantity?

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It will depend on the quantity of your ferric chloride

Also now if I add sodium carbonate over the already added naoh will it be a problem (or could fix the issue) ?

Click to expand...

I guess you will have problem,stick to NaOH only...
You just need to naturalize the solution .... before disposal

I used Sodium Carbonate ... as I find it more suitable for this job
In my website I have an article on this ... http://royhomes.edaboard.eu/pcb/tonnertransfer.html
Check the "Etching with Ferric Chloride" section

Forgot to tell one thing. When I took this back after this, the container bottom was hot..

Click to expand...

Its normal its an exothermic reaction so it will produce heat...


Good Luck

Actually I added some NAOH, no reactions....... but container bottom was hot. what does that mean ? what I have read in documents - when adding NaCo3 or Naoh , the reaction causes It to become foam like and will almost overflow initially.
What do you suggest I keep adding this until it happens?

sunil21 said:

Actually I added some NAOH, no reactions....... but container bottom was hot. what does that mean ?

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The reaction is exothermic, which quickly heats up the solution, and is also proof that there is a reaction going on. What happens is the following, presumably:
FeCl2 + 2NaOH => Fe(OH)2 + 2NaCl
CuCl2 + 2NaOH => Cu(OH)2 + 2NaCl
FeCl3 + 3NaOH => Fe(OH)3 + 3 NaCl
The last reaction is from the left over, unused FeCl3 in the solution. Since there are no gases produced in either reaction, you won't notice any bubbling. And while NaOH is a white powder and colorless in solution, all the hydroxides are rust brown. Hence, you'll hardly notice the color difference before and after the reaction.

While Fe(OH)2 and Fe(OH)3 are simply iron rust and harmless, copper salts are not. There is no easy way to separate iron and copper salts. The best way to dispose of it is letting the (insoluble) hydroxides precipitate to a crust and pouring off the clearer liquid to reuse the excess NaOH solution. Tip: I use NaOH as developer, so I have both chemicals readily available at all times! When the crust has dried, I bring it to a metal recycling station.

Adding Na2(CO)3 is a bad idea, by the way, because the reaction is
Na2(CO)3 + FeCl2 + H2O => Fe(OH)2 + 2NaCl + CO2
Which will cause the solution to bubble because CO2 is released in gaseous form. And since FeCl3 strains are really hard to remove, you should avoid splashing at all costs.

Thanx for the reply.

So I keep adding NAOH to neutralize the solution. so the solution will change the color in the end or what?
How do I know (with no bubbling etc) the entire neutralizing is complete?
(BTW) I used Dry film photoresist method for pcb , so I had with me some NACO3 and NAOH, NAOH was leaked and so I had to get rid of it. so then I bought 0.5 KG of NAOH (min. available to buy). So with that much quantity of NAOH , I started using NAOH for this neutralization. I only have small quantity of NACO3 (I don't know how much will be required for this purpose, what if the quantity I have is not enough? so I may be stuck half way). If I had 1/2 kg of NACO3 , I sure would have used it (it is already powder).

one more question( for future disposals) - which one is good - NACO3 or NAOH?

sunil21 said:

one more question( for future disposals) - which one is good - NACO3 or NAOH?

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For future disposals, do NOT use Na2CO3: in reaction it will cause bubbling, bubbling causes splashing and splashing is bad when you're dealing with corrosive substances!

Neither NaOH or Na2CO3 do not dissolve well in a low pH, so it's best to make a (concentrated) solution of NaOH and then add that to the FeCl3/FeCl2/CuCl2 mixture you want to neutralize. Upon pouring a solution of NaOH in the ferric chloride, you can see a brown cloud of hydroxides forming if you're looking closely.

Another tip: dissolving solid NaOH in water is also an exothermic reaction, and depending on the concentration the solution can get really hot. Therefor I recommend to simply buy these solutions. In most of Europe you can find them in hardware stores as liquid drain cleaners, with a concentration between 20% and 30% NaOH. I dilute these solutions to develop my boards, and use the concentrated solution to dispose of ferric chloride.

When neutralizing ferric chloride, feel free to use an excess of NaOH to make sure all chlorides are properly converted to NaCl.

I appreciate your effort mr.ArticCynda.

I am from india.


While Fe(OH)2 and Fe(OH)3 are simply iron rust and harmless, copper salts are not. There is no easy way to separate iron and copper salts. The best way to dispose of it is letting the (insoluble) hydroxides precipitate to a crust and pouring off the clearer liquid to reuse the excess NaOH solution. Tip: I use NaOH as developer, so I have both chemicals readily available at all times! When the crust has dried, I bring it to a metal recycling station.


so I assume from your previos post that "I keep adding NAOH " until I get a colorless solution like water which I can pour down. Copper smuges at the bottom which I will mix with plaster of paris .

Correct me if I am wrong?

sunil21 said:

so I assume from your previos post that "I keep adding NAOH " until I get a colorless solution like water which I can pour down. Copper smuges at the bottom which I will mix with plaster of paris .

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This is essentially correct yes, however, when the hydroxides are formed in solution they are extremely finely dispersed, and thus it might take a while before they sink to the bottom of the reaction vessel. What I typically get is a thick smudge of dark brown hydroxides at the bottom and a lighter colored liquid above it. It never gets water clear.

If your quantities aren't too big (i.e. do not require a continuous process), I'd recommend to neutralize the ferric chloride with an excess of NaOH and just wait until the water evaporates. Both the unreacted NaOH as well as completely harmless NaCl (= table salt) will dry out with the hydroxides, but this isn't a huge problem.

If you're interested in making PCBs yourself I can highly recommend you this article: https://www.ijeir.org/administrator...arch/files/publications/IJEIR-454 Final N.pdf