Ammonium Persulfate disposal

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Engineer1138
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Ammonium Persulfate disposal

Post by Engineer1138 » Wed Feb 08, 2006 2:58 pm

I have always used Ferric Chloride for etching boards. On average, though, I only make about one prototype a year on my own: I've gotten spoiled by the cheap online vendors :-)

However, I can get my hands on a quantity of ammonium persulfate etchant at very low cost. Are there any disposal issues with this stuff, or is it just "dilute it and flush?"

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Chris Smith
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Re: Ammonium Persulfate disposal

Post by Chris Smith » Wed Feb 08, 2006 3:36 pm

You can always dehydrate it and make rocket fuel out of it. The more metal eched into it, the better it is.

Actually you can incinerate it as long as your state or county doesn’t have strict smog laws.

Washing it pure into the water table or using it as a fertilizer by it self is harmless, its the metals it etches out of the board and takes with it that are bad for the ground water and food consumption.

However if its just a decorative plant, you could use small amounts for fertilizer even with disolved lead, copper, and tin.

Mix in a little baking soda in case the PH is a little too high or low for the plant.

And try it out on your mother in laws plants first, just in case?

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haklesup
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Re: Ammonium Persulfate disposal

Post by haklesup » Wed Feb 08, 2006 4:48 pm

If it had a high copper content, it would act like any other copper ion containing solution and kill plants and most things in the soil.

If it had lead, it would be as bad as scraping lead based paint into the ground.

Tin would probably be somewhat less problematic

Naturally the concentration of the metals would make a difference.

For small amounts, it should be safe (though not necessarily permitted) to dilute and flush. In larger quantities, it can corrode your pipes directly. (some sinks have P-traps made of chrome plated brass or copper which will corrode quickly, Use PVC or ABS to replace if this happens.)

Your city would probably prefer you collect it into a bottle (diluted) and bring to a hazmat dump per the MSDS sheet.

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Chris Smith
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Re: Ammonium Persulfate disposal

Post by Chris Smith » Wed Feb 08, 2006 6:06 pm

Plants like people need metals, minerals, and vitamins as long as they are not in a heavy concentration or out of their useful PH balance.

Metals such as lead and copper are beneficial to some plants and their health.

Copper in the Environment
In plants, copper is especially important in seed production, ... Although copper concentrations in plants tend to increase with increasing copper ...
www.ene.gov.on.ca/cons/4141e.htm

Copper
In copper-deficient plants, the rate of photosynthesis can also be reduced for ... -Resupplying copper to deficient plants can restore the activity of ...
www.msu.edu/course/css/853/Copper.html

Lead in Garden Soils and Plants Since plants do not take up large quantities of soil lead, the lead ... Lead is relatively unavailable to plants when the soil pH is above this level. ...
www.grayenvironmental.com/lead_in_garden_soil.htm

<small>[ February 08, 2006, 06:08 PM: Message edited by: Chris Smith ]</small>

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philba
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Re: Ammonium Persulfate disposal

Post by philba » Wed Feb 08, 2006 6:29 pm

sheesh, nothing like helping the guy...

I love AP. No stains and its clear so you can watch the process of your etch.

best way to dispose of AP is to dehydrate it and wait for a local hazardous household waste disposal event. I put a jar of spent AP on a hot plate set to low and all that's left are some crystals.

By the way, AP works a lot better at 120-130F (or hotter). I use a hacked aquarium heater.

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Re: Ammonium Persulfate disposal

Post by Yerry » Wed Feb 08, 2006 6:57 pm

You can sure tell which answers are sincere and which ones are pure BS.

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philba
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Re: Ammonium Persulfate disposal

Post by philba » Wed Feb 08, 2006 11:30 pm

technically, I'm sure the facts are correct but it reminds me of a joke...

Two guys are flying in an airplane in Seattle and a dense ground fog comes up very quickly. They circle and circle and circle looking for a break in the fog. Suddenly a hole opens up and they see a guy standing on the roof of an office building. The pilot opens the window and shouts down "where am I". The guy on the building yells back, "you're in an airplane". The pilot immediately banks, executes a series of turns and lands at the airport. The passenger is amazed - "How did you figure it out?". The pilot says "Well the guy gave me a perfectly correct but totally useless answer so I must have been over Microsoft Technical Support. From there it was easy."

Tommy volts
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Re: Ammonium Persulfate disposal

Post by Tommy volts » Thu Feb 09, 2006 6:57 am

Chris,

It's true that people need metals and minerals in their diet. However, it takes nature millions of years to break down raw metals (iron for example) into dietary metals.

Engineer1138
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Re: Ammonium Persulfate disposal

Post by Engineer1138 » Thu Feb 09, 2006 7:58 am

OK, so it seems like the best method is to evaporate it and store the crystals until I can dispose of them safely. I like that: my water comes from a well just outside the house, so I'm a bit paranoid about what ends up in the soil!
Thanks guys.

Now I'm off to gnaw on an iron bar :-)

jimandy
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Re: Ammonium Persulfate disposal

Post by jimandy » Thu Feb 09, 2006 9:09 am

I'm wondering. If you still have life left in the solutiion then evaporate it down to crystals, could you not mix the crystals with water later and be back to a useable solution?

<small>[ February 09, 2006, 09:10 AM: Message edited by: jimandy ]</small>
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philba
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Re: Ammonium Persulfate disposal

Post by philba » Thu Feb 09, 2006 11:05 am

When it's spent, its gone. There may be a way to regen it, though. If you let used AP solution sit, slightly blue crystals precipitate out. They disolve in the heated solution. Spent solution is a very strong blue color - Copper Sulfate, I suspect. I suppose you could evaporate non-spent solution and then remix it, though. I wonder if you could decant the solution from the crystals - assuming they are all copper sulfate.

I think the AP + copper turns into copper sulfate and ammonia (and some h2o). I did a quick look but couldn't find the reaction equation. I don't smell ammonia when etching but suspect its a very small amount.

Anyone know the AP+Cu chemistry?

<small>[ February 09, 2006, 11:08 AM: Message edited by: philba ]</small>

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Chris Smith
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Re: Ammonium Persulfate disposal

Post by Chris Smith » Thu Feb 09, 2006 11:17 am

First of all, per chlorate crystals are fine, but heat on them isn’t. Not saying you cant do it, just don’t agitate it after you form crystals.

Remember the plant that blew up in Nevada, with the power of a small A bomb? Tons of Per chlorate and metals involved.

I know because I have made many a noise maker, [or should I say earth mover] out of perchlorates. Some go off just looking at them with the wrong attitude! The longer they stay a crystal mix, the more unstable they tend to get.


As to plants, YES, they are still in mother natures role playing out their million year cycles of growth, absorbing metals, minerals, etc, so yes,... plants love the stuff as long as you don’t OD them on a strong batch, and as long as you naturalize their PH over all so the plant doesn’t get burnt.

Ground water NO, potted plants yes. Humans need different forms of metals and minerals.

Try one plant at a time to make sure that plant likes it, or do a web search to make sure lead and copper are on its particular menu.

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haklesup
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Re: Ammonium Persulfate disposal

Post by haklesup » Thu Feb 09, 2006 1:14 pm

"Naturally the concentration of the metals would make a difference."

My assumption was that a solution used to etch copper PCBs would end up with a rather high concentration (perhaps as high as saturated) of copper when depleated.

Blue crystals (or solution) is the appearance of copper sulphate which is sometimes used to keep roots out of drain pipes (or where ever)
http://www.pestproducts.com/k77rootkiller.htm (though at very high concentrations for this application in pipes, when applied directly to soil in the vicinity of excavated pipes, is an effective root inhibitor at lower dilutions)

Copper IS beneficial but only as a Trace mineral. I suppose if you etched only a few boards in a decent sized bath it might not be so high. A single application to a house plant just might help but since CU is an element, it will not break down and is cumulative, one should not use it regularly as you would a nitrate fertalizer.

At medium concentrations (10%-20%)it is a very effective mildewcide and fungacide but as concentration increases it becomes toxic to more and more things, particularly fish.
http://extoxnet.orst.edu/pips/coppersu.htm

Diluted, a used etch bath might work as a fungacide for say rose plants. Any remaining nitrates should be beneficial too. Sulpher is usually not a problem in soil and is also a fungacide and plant nutrient in its own right.

Probably not advised but interesting to note: pouring it on your firewood to dry should yeild interestingly colored flames in the fireplace. (green I think)

What you can do and what you should do I will leave up to you.

jimandy
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Re: Ammonium Persulfate disposal

Post by jimandy » Thu Feb 09, 2006 2:09 pm

Would it be possible through electrolysis to remove the copper?
"if it's not another it's one thing."

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Bob Scott
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Re: Ammonium Persulfate disposal

Post by Bob Scott » Thu Feb 09, 2006 3:12 pm

Philba,

[QUOTE]Originally posted by philba:
[QB] When it's spent, its gone.

Have you ever tried feeding aluminum to ammonium persulphate or ferric chloride etchants? DON'T FEED THEM TOO MUCH AT ONCE! It is a fast reaction, generates heat and may bubble all over the place.

I'm wondering if alumimum and the so-called "spent" etchant would also react violently, with Al molecules replacing the Cu molecules.

Bob

<small>[ February 09, 2006, 03:16 PM: Message edited by: Bob Scott ]</small>
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