Tim,

Thank you very much for the quick response.


---- Tim Williams wrote:
>Yeah, you could hook up a 5V supply to a couple of electrodes, minding that the positive will corrode so you want to use something corrosion-resistant like sheets of solid graphite (probably not terribly cheap). Copper will plate out on the cathode (negative).

Not being a trained chemist / scientist, would both the anode and cathode
consist of graphite? By the way, I think I can find a relatively cheap source
for solid graphite: fishing rods / golf clubs (OK maybe not the latter). What
type of amperage are we talking here? I am assuming that you are talking about DC, yes? This is, perhaps, the most promising solution for reasons I state below.


> The pool guys probably say you can't because either there's a constant source, or there simply isn't enough to remove it from solution. Even copper metal has some solubility in water, and concievably a lot could dissolve in a whole swimming pool. And that's just pure water; you have all kinds of salts and chlorine and stuff to keep it clean. The chlorine tends to oxidize copper to cupric ions, usually a deep green (concentrated) or light blue (dilute) color
(probably easy to miss against water's normal blue color). Especially if the
pool is acidic, you could hold a lot of copper in solution.

No, there is no constant source. This winter, our outdoor fire pit (copper
bowl) got blown into the pool. I didn't realize it until very recently. I am
positive that this is the source as all the pool plumbing is PVC. And it's true
that the pH of the water was slightly acidic over the winter (about 6.8 or so). I noticed the green effect when I began to open the pool: adjust ph to ~7.2 and dumped in a boat load of 6% bleach, in effect getting about 20 ppm of chlorine to kill off algae (this level of chlorine was maintained for about a week). At first, I thought it *was* the algae, but as the shocking continued, the pool cleared up but stayed green. I am guessing that since I brought the pH into nominal for pools and then dumped in the chlorine the copper precipitated out of the water and attached itself firmly to my pool liner.


> So lemme see... you can try to find a stronger, insoluble complex. EDTA
(lemme see if I remember that, ethylene diamine tetracetate, yeah think so) is used to complex heavy metals in food and blood, to help prevent spoilage or cure heavy metal poisoning. You should be able to dump in a few ounces or pounds, run the filter and see if that clears it up.

I googled EDTA and it turns out that the main component of "Metal Out",
mentioned previously, is EDTA with a twist, MSDS lists its chemical name as:
Ethylenediaminetraacetric Acid Tetresodium Salt. Salt being the difference.
Could this possibly cause the chemical in "Metal Out" to be weaker than other
sources? The problem here is that even though this works, it's temporary as
indicated in my earlier email. As I understand it, my pool filter (diatomaceous
Earth) filters particles no smaller that 5 microns when clean and presumably
when EDTA binds with the copper in solution the particles are smaller than I can filter. Can you shed light on that?


> Other ways to remove copper are to raise the pH, precipitating copper
hydroxide as a green or blue sludge (if it isn't present as a complex that's
soluble in basic pH!), or to add a reducing agent (such as sodium sulfite) that
converts it to cuprous ions, or metallic copper. Cuprous ions are less soluble
and will precipitate as either white cuprous chloride (which turns green in
moist air because it would rather be the oxidized form!) or yellow to orange to brick red cuprous oxide, otherwise known as the mineral cuprite.

Yes, this is my experience. Unfortunately it precipitates right onto the liner
of my pool and no amount of scrubbing takes it off.

As you can see, this is a perplexing problem for pool owners and someone could make a mint off of a permanent solution. Which of course leads me to believe that a.) there isn't one and b.) it's too expensive for pool owners. Of the two, I have to think "a" is the answer because we spend WAY TOO MUCH money in general.

So, having bored you to death by now, a method to remove the copper via
electrolysis seems to have some promise.


Tim,

Thanks again for taking the time to help me solve a problem pool owners have been dealing with (unsuccessfully -- as in not permanent) forever. I truly appreciate the effort, especially considering we are total strangers. It's
great to live in the information age, where a guy looking to fix his pool can
get advice from an expert.

Best regards,

Troy

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