EMRFD Message Archive 7482

Message Date From Subject
7482 2012-05-08 06:05:33 Ashhar Farhan disposing of the etchant
i am using hydrochloric acid and hydrogen peroxide to etch some pcbs.
what is a safe way to dispose this the etchant? i have heard that one
can throw in sodium hydroxide pellets into it until it turns into
solid copper and salt water. is this true? i don't have access to any
'safe disposal' systems where i live. any help will be appreciated.

i have heard about regenerating the etchant but sooner or later the
etchant is going to grow bigger than the bottle...

- farhan
7483 2012-05-08 09:57:01 Paul Anderson Re: disposing of the etchant
Be careful with sodium hydroxide. It's fierce stuff. Is this a mixture of hydrochloric acid and hydrogen peroxide?

Sent from my iPad

On 2012-05-08, at 9:05 AM, Ashhar Farhan <farhanbox@gmail.com> wrote:

> i am using hydrochloric acid and hydrogen peroxide to etch some pcbs.
> what is a safe way to dispose this the etchant? i have heard that one
> can throw in sodium hydroxide pellets into it until it turns into
> solid copper and salt water. is this true? i don't have access to any
> 'safe disposal' systems where i live. any help will be appreciated.
>
> i have heard about regenerating the etchant but sooner or later the
> etchant is going to grow bigger than the bottle...
>
> - farhan
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
7484 2012-05-08 10:05:30 Ashhar Farhan Re: disposing of the etchant
yes, it is a 2:1 mixture of hydrogen peroxide and hydrochloric acid. i have
heard that one could add NaOH to it so, the toxic copper salt is turned to
copper and common salt.

- farhan

7485 2012-05-08 10:14:48 Tim Hills Re: disposing of the etchant
I live in a big enough city that the impact on the sewage system from
the rare times and small amounts of etchant I use in negligible if I
flush it down the throne.

Wouldn't do that with a septic system though.

Tim Hills
Sioux Falls, SD

7486 2012-05-08 10:23:04 Paul Anderson Re: disposing of the etchant
If I figure right, you'll get copper chloride and water. If you add some phenolphthalein solution you'll be able to tell when the acid is properly neutralized. Copper chloride might be problematic, it's fairly soluble in water. Copper carbonate, however, is insoluble. If you add sodium carbonate(washing soda) or sodium bicarbonate(baking soda), you should get sodium chloride and copper carbonate.

Be careful, as I recall this is exothermic. Do it outside and add the base slowly.

Sent from my iPad

On 2012-05-08, at 1:05 PM, Ashhar Farhan <farhanbox@gmail.com> wrote:

> yes, it is a 2:1 mixture of hydrogen peroxide and hydrochloric acid. i have
> heard that one could add NaOH to it so, the toxic copper salt is turned to
> copper and common salt.
>
> - farhan
>
>
7487 2012-05-08 11:41:15 Leon Heller Re: disposing of the etchant
7488 2012-05-08 13:59:46 Tamás Fábián Re: disposing of the etchant
Hi,

it just popped into my mind: if you guys can't get NaOH directly, you
probably still be able to acquire certain drain cleaners with high NaOH
content. It'll do the trick too. It's a ferocious chemical, be careful.

Cheers,

Tamas HA5FTL.

On 8 May 2012 20:41, Leon Heller <leon355@btinternet.com> wrote:

> **
>
>
>
7489 2012-05-08 14:16:10 Paul Anderson Re: disposing of the etchant
It's used for saponification of animal fats by those making soap. Sold as lye. When handling it, use gloves and splash goggles. NaOH in the eyes can blind you in under fifteen seconds.

Sent from my iPad

On 2012-05-08, at 4:59 PM, Tamás Fábián <giganetom@gmail.com> wrote:

> Hi,
>
> it just popped into my mind: if you guys can't get NaOH directly, you
> probably still be able to acquire certain drain cleaners with high NaOH
> content. It'll do the trick too. It's a ferocious chemical, be careful.
>
> Cheers,
>
> Tamas HA5FTL.
>
> On 8 May 2012 20:41, Leon Heller <leon355@btinternet.com> wrote:
>
>> **
>>
>>
>>
7490 2012-05-08 18:54:46 Ashhar Farhan Re: disposing of the etchant
I have used NaOH pellets as a kid! Nasty stuff. I have been
recommended baking soda as well. That looks safer and easier to get as
well. Lemme try that out today....
- Farhan

On 5/9/12, Tamás Fábián <giganetom@gmail.com> wrote:
> Hi,
>
> it just popped into my mind: if you guys can't get NaOH directly, you
> probably still be able to acquire certain drain cleaners with high NaOH
> content. It'll do the trick too. It's a ferocious chemical, be careful.
>
> Cheers,
>
> Tamas HA5FTL.
>
> On 8 May 2012 20:41, Leon Heller <leon355@btinternet.com> wrote:
>
>> **
>>
>>
>>
7491 2012-05-08 21:23:11 Paul Anderson Re: disposing of the etchant
One quick point: copper carbonate likes to stain things. It can be difficult to get off things short of using acid. I don't foresee it being a real problem in your situation, but it can be a nuisance if you want to use a container for other things. It's a light blue color.

Sent from my iPhone

On 2012-05-08, at 9:54 PM, Ashhar Farhan <farhanbox@gmail.com> wrote:

> I have used NaOH pellets as a kid! Nasty stuff. I have been
> recommended baking soda as well. That looks safer and easier to get as
> well. Lemme try that out today....
> - Farhan
>
> On 5/9/12, Tamás Fábián <giganetom@gmail.com> wrote:
>> Hi,
>>
>> it just popped into my mind: if you guys can't get NaOH directly, you
>> probably still be able to acquire certain drain cleaners with high NaOH
>> content. It'll do the trick too. It's a ferocious chemical, be careful.
>>
>> Cheers,
>>
>> Tamas HA5FTL.
>>
>> On 8 May 2012 20:41, Leon Heller <leon355@btinternet.com> wrote:
>>
>>> **
>>>
>>>
>>>
7492 2012-05-09 05:43:06 Jon Iza Re: disposing of the etchant
Folks,
when you use Hydrochloric acid+hydrogen peroxyde, you are oxidizing
the cooper metal to an oxidized cooper ion which is soluble.
There are two soluble cooper ions, Cu(I) and Cu(II), which lead to
cuprous and cupric salts, respectively.
Cu(II) is also an oxydant, and may eat solid Cooper from PCBs.
That is the basis of the method using Cupric Chloride with some acid
added (which is needed to keep all those salts soluble). Without the
acid, when the pH of the medium become alcaline some precipitates may
appear.
So Cu(II) attacks solid cooper -Cu(0)- forming Cu(I) which remains in
solution when acid is present.
The best part is that you may regenerate the medium by just bubbling
air through it. The oxygen from air oxidates the newly formed Cu(I) to
Cu(II) and, voilà!, fresh medium.
And you may do it again and again without worrying about destroying
your sink pipes.

Should you want to know more, here you have the gory details:

http://techref.massmind.org/techref/pcb/etch/CuCl2.htm

In case you want to get rid of it, take care and do not use any sink
with chromed parts. They may get discoloured. Also, never send the
stuff to a septic tank unless you want to dope your friendly microbes
with lots of copper. They may stop doing their work.

jon, ea2sn

--
Jon Iza
Professor of Environmental Technologies
University of the Basque Country
Ham: EA2SN -since 1978-
7494 2012-05-09 10:51:32 scriabini Re: disposing of the etchant
The resultant Copper Chloride is useful to
gardeners as a root killer or root control
agent. It may be used to kill any roots
which penetrate home sewage drain lines
(except in those locales where its use is
prohibited.)

If it were me I'd evaporate it to concentrate
it then put it into labeled bottles. Then I'd
call local nurseries and garden shops to see
if they'd like to have it.

Or place an "offer" with "FreeCycle" or
offer it