etchant disposal

[Mcgyver]

I'm about to try etching for the first time and am using Ammonium Persulphate crystals. I've built a tank with heater and bubbler and have read a lot on the subject, but before I make up the etchant I'd really like to know what to do with it afterwards? I've found instructions for Ferric Chloride, but not what do with the Ammonium Persulphate - ie how to neutralize/dispose of it.

also, the msds says to store in a vented container because it gases - that doesn't sound like something one would want around the shop??

So can anyone help me with a practical/environmentally responsible approach with what do with etchant afterwards?? thx

[anoel]

Pour it in the toilet and flush it, is the typical way to dispose. When it mixes with enough water it basically becomes inert through dillution.

[ger21]

A quick google search shows a lot of msds sheets that say to treat it as a hazardous waste.

When it mixes with enough water it basically becomes inert through dillution

Until everybody does it, and then it's not so diluted anymore.

[damae]

MSDS for FeCl:

http://www.jtbaker.com/msds/englishhtml/f1060.htm

A few quotes:

"US Regulations (CERCLA) require reporting spills and releases to soil, water and air in excess of reportable quantities. The toll free number for the US Coast Guard National Response Center is (800) 424-8802."


"Whatever cannot be saved for recovery or recycling should be managed in an appropriate and approved waste facility. Although not a listed RCRA hazardous waste, this material may exhibit one or more characteristics of a hazardous waste and require appropriate analysis to determine specific disposal requirements. Processing, use or contamination of this product may change the waste management options. State and local disposal regulations may differ from federal disposal regulations. Dispose of container and unused contents in accordance with federal, state and local requirements. "


Of course, I don't know how well this applies to FeCl that has been neutralized with copper...

[Mcgyver]

thanks for the responses. Using a combo of google, the manufacturer and a chemistry forum I was unable to address this in what i would call a environmentally friendly manner. It seems that anoel is correct, although few admit to it. Basically the chemist at the manufacturer said to neutralize it with baking powder and flush it. Reading between the lines, I got the feeling he thought my environmental concerns were noble, but that it was a first for him. He had no advice on how to neutralize, extract or otherwise deal with the copper ions which I understand is a toxic heavy metal and as far as he knew everyone just flushed it. one more reason to make a circuit board mill.

[Chris D]

I am just getting into etching too so I know nothing yet, but, can't you just put the product somewhere, in a container with holes in it, away from people that could get to it, and simply let it evaporate?

I would guess it is primarily water, which should evaporate. When it's done evaporating, all that should be left is the copper, and perhaps some other dried "stuff" which will be very minimal is size. Then this could be disposed of much more easily and economically than the full liquid state of the product.

Chris

[H500]

Do a search for copper chloride. It's essentially a mixture of HCL and hydrogen peroxide. This etchant never needs to be disposed since it can be regenerated indefinitely by bubbling air through it. I haven't tried it yet, since I can't find a local source for 30% peroxide.

HCL is easy to get and dirt cheap ($8 for 4 liters in Canada).