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[Questions] PCB etching, environment & safe disposal - how?

PostPosted: 13 Mar 2009, 07:18
by flood
and now for something completely different...

i etch PCBs using hydrochloric acid and hydrogen peroxide. this process is quick, efficient and seems to leave no horrible stains all over the place like FeCl3 does. it does leave me with a major problem, namely safe disposal of the CuCl2 solution left behind.

now, the simple solution would be to let the water evaporate until only the crystals are left behind and hand those over to the correct authorities, right? problem - i live in INDIA. we have nothing in the way of collection of hazardous goods or anything of the sorts. effluents, garbage, chemicals, you name it are dumped into the closest water body.

i don't like the idea at all though. so i need help...

this is what i did -

a. first batch - i took the used etchant and dumped baking soda (backpulver) into it until it would no longer effervesce. then i let it sediment and poured off the clearish liquid (an aggressive base) on the top into a beaker. using a pH meter i added HCl till it was around pH 7, diluted it with water and poured it down the drain. i think that should be quite safe. i still have the copper sediment - no idea what that is now, my chemistry lessons are failing me here. how do i get rid of it safely?

b. second batch - my current batch of etchant is still going strong, have done a few PCBs with it already - HCl, H2O2. it is going quite blue now, and i would like to think of a better method than method a. is it possible to electrolyse the copper out? does anyone know of any simple rig that could achieve this?

thanks to all on this great forum for any suggestions - i want to do my bit for the environment, status quo and lackadaisical attitude in this country be damned.

Re: PCB etching, the environment and safe disposal - how?

PostPosted: 13 May 2010, 07:29
by flood
rise, my undead thread, rise! i have a lot of copper chloride etchant in bottles now.... :(

Re: PCB etching, the environment and safe disposal - how?

PostPosted: 13 May 2010, 15:22
by lolbou
By adding sodium hydroxide in your solution, you'll get Cu(OH)2, which is a solid. Just filter it and your copper is out. Chloride ions are cool for water, and your copper is out!

Electrolyse would be nice to get the copper back to its metal form, but I have to check if there is any risk of chlorine to be formed in the process (on the other electrode)...

BUT I doubt your copper quantities are large, especially considering that most of the domestic pipes are made with copper... And copper is an essential dietary mineral, though I agree that a large quantity in waters is a mess...

Re: PCB etching, the environment and safe disposal - how?

PostPosted: 13 May 2010, 20:51
by Grendahl
lolbou wrote:By adding sodium hydroxide in your solution, you'll get Cu(OH)2, which is a solid. Just filter it and your copper is out. Chloride ions are cool for water, and your copper is out!

Electrolyse would be nice to get the copper back to its metal form, but I have to check if there is any risk of chlorine to be formed in the process (on the other electrode)...

BUT I doubt your copper quantities are large, especially considering that most of the domestic pipes are made with copper... And copper is an essential dietary mineral, though I agree that a large quantity in waters is a mess...



Why don't you just re-energize your etchant by adding more oxygen to it bubbling air through it? You'll go back to an almost clear color, and there's no possible way to add too much oxygen to the mix via bubbling. The etchant will simply stop accepting more when it's fully oxygenated. (if you don't have an old aquarium air pump to bubble with, you can always leave it out in an open container (with a lot of surface exposure between liquid and air)... but this method takes some time.

That, or you could add a couple capfulls of hydrogen peroxide solution... but go sparingly if you use this method, as the solution most readily available is 97% water.

Re: PCB etching, the environment and safe disposal - how?

PostPosted: 13 May 2010, 21:01
by lolbou
Grendahl wrote:Why don't you just re-energize your etchant by adding more oxygen to it bubbling air through it? You'll go back to an almost clear color, and there's no possible way to add too much oxygen to the mix via bubbling. The etchant will simply stop accepting more when it's fully oxygenated. (if you don't have an old aquarium air pump to bubble with, you can always leave it out in an open container (with a lot of surface exposure between liquid and air)... but this method takes some time.

That, or you could add a couple capfulls of hydrogen peroxide solution... but go sparingly if you use this method, as the solution most readily available is 97% water.


Adding oxygen won't help to get rid of the copper... :roll:

Re: PCB etching, the environment and safe disposal - how?

PostPosted: 14 May 2010, 04:12
by Grendahl
lolbou wrote:
Grendahl wrote:Why don't you just re-energize your etchant by adding more oxygen to it bubbling air through it? You'll go back to an almost clear color, and there's no possible way to add too much oxygen to the mix via bubbling. The etchant will simply stop accepting more when it's fully oxygenated. (if you don't have an old aquarium air pump to bubble with, you can always leave it out in an open container (with a lot of surface exposure between liquid and air)... but this method takes some time.

That, or you could add a couple capfulls of hydrogen peroxide solution... but go sparingly if you use this method, as the solution most readily available is 97% water.


Adding oxygen won't help to get rid of the copper... :roll:


That's true. But after the first few etches are done with the HCL, it's the cupric chloride that does the etching. This stuff should be like sourdough starter. I haven't run into this situation on mine yet, but I also don't do a whole lot of etching. Bubbling has always worked fine for me with the low volume of boards I do. Even with the extra copper.

Re: PCB etching, the environment and safe disposal - how?

PostPosted: 14 May 2010, 04:32
by Grendahl
http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html
That link, along with the one on my own site, addresses the process. I haven't had any disposal issues yet, but I can see from this topic that I am going to have to research it. :)

I'll let you know what I come up with.

Re: PCB etching, the environment and safe disposal - how?

PostPosted: 14 May 2010, 05:23
by flood
regenerations sounds like a good idea... while i certainly am not running an industrial sized etching rig ( i etch in a plastic ice cream tray lol) i'd like to do as much as i can to conserve... so thanks for the help so far, and keep the ideas coming.

Sodium persulfate disposal

PostPosted: 02 Jun 2010, 23:29
by menlow
I'm finally ready to etch my first pcb with some sodium persulfate I got from Steve over at Small Bear. I emailed him about how to dispose of the used stuff and he said he thought the copper left over after evaporation was safe to pitch, but that I should check with a certain 'other' forum. I've got a pregnant wife and a few pets I'm trying to look out for, so does anyone have any info as to how to get rid of the used solution? I've checked the MSDS sheet and it vaguely says something about "disposal in accordance with federal and state laws." I really want to do this the right way so any help is greatly appreciated. Thanks!

Re: Sodium persulfate disposal

PostPosted: 06 Jun 2010, 02:36
by DeanM
Its prob classed as a "hazardous waste" like ferric chloride that people also use to etch. It would have to be disposed of at a hazardous waste disposal place or something, not really sure! but its good to hear your not dumping it. if you plan to etch on a regular basis there is another etching solution that can be reused over and over that you could check out aswel. it takes a lot more preparation but is straight forward enough. I posted a thread on here recently about it. it had been posted before that aswel.

Re: Sodium persulfate disposal

PostPosted: 06 Jun 2010, 11:22
by salocin
I just flush it down the toilet.

Re: Sodium persulfate disposal

PostPosted: 06 Jun 2010, 12:03
by rocklander
I've been informed that the used ferric chloride is not really any danger to anything other than marine life (and that's the copper, not the FeCl). I pour mine into the garden as there's little chance it'll make it to any waterways. it shouldn't be any danger to my dogs, but to be sure I pour it into an area they can't get to.

Re: Sodium persulfate disposal

PostPosted: 07 Jun 2010, 02:50
by menlow
Thanks for the info guys. It seems ridiculous that when I go to Google and type in 'sodium persulfate disposal' I can't get an answer that's worth a turd.

And btw I did try to etch my first board - failure. I put the etchant in a plastic bowl and put it inside a larger bowl and kept filling the outer bowl with hot water. I agitated it every couple minutes, and it took forever. I have no idea what I did wrong. I even followed Steve's instructions from his website... When it didn't etch fast enough I added some more crystals. The whole thing kind of bummed me out, but I'll get back at it tomorrow.

Re: Sodium persulfate disposal

PostPosted: 09 Jun 2010, 11:24
by DeanM
menlow wrote:And btw I did try to etch my first board - failure. The whole thing kind of bummed me out, but I'll get back at it tomorrow.

I have yet to do any of my own etching but i have stuff ordered so will hopefully start experimenting soon. I dont expect to get it right the first time either! so dont worry man im sure ya'l get it right the next time! let us know how it goes!

Re: Sodium persulfate disposal

PostPosted: 10 Jun 2010, 03:42
by menlow
DeanM wrote:so dont worry man im sure ya'l get it right the next time! let us know how it goes!


Thanks man! I did try a pair of boards yesterday - a Stratoblaster and an SHO. They etched ok (the secret was to get the etchant/water mix almost boiling before dropping the boards in!), but I don't have any way to drill the pcbs right now. If I can wait til this weekend, I can use my pop's drill press. But in the meantime I ordered some vero to tinker with. I need to get a Stratoblaster built for my father-in-law for father's day and I think the vero will make a simple circuit even simpler!