Is GFO a type of exchange material?

[Reeferdood]

Good morning Randy,
we had a conversation recently about GFO and copper. Well this experiment is still ongoing and the one performing the experiment is still finding copper. He feels that in order for the copper to be "released" per se from the GFO there has to be phosphate available, does this even sound possible?
He is still finding copper elevating after running this with his tank water in a sterile bucket over 5 days. He has found no elevation in copper with freshly mixed saltwater doing the same experiment.
Thanks for your help in this matter.

 

[Dr. Reef Verified Sponsor]

Gfo will absorb free copper and total copper quite well but not exceedingly well. While gfo has hardly any effect of absorption on complex copper like chelated or ionic.

If this gfo had absorbed copper at some point of time and now if in use in the tank, it will release copper to make room for phos.
Highly possible.

 

[Reeferdood]

Interesting... Thank you for your input in this experiment.

 

[Randy Holmes-Farley Verified Community Expert]

I don't understand the experiment. He has copper in freshly mixed seawater? Why use GFO when designed metal binders are available?

This question is a lot more complicated than it seems. In short, then answer is certainly that copper bound to GFO can be released from GFO in the absence of phosphate, but also that phosphate might (or might not) cause bound copper to be released.

An ion exchange resin, like in an RO/DI MUST release an ion to bind another ion.

GFO is much more complex, in terms of the chemistry taking place at the surface, but it is not a swap the way that an ion exchange resin is.

Copper is also extraordinarily complicated in seawater since most or all of it is already bound to organic matter in reef tanks and in the ocean. It is not necessarily just Cu++ ion binding to GFO. It might be some of that. But it also may be the organic complex binding to GFO (or GAC, purigen, etc.)

FWIW, many things will bind to and/or interact with GFO.

 

[Reeferdood]

I don't understand the experiment. He has copper in freshly mixed seawater? Why use GFO when designed metal binders are available?

This question is a lot more complicated than it seems. In short, then answer is certainly that copper bound to GFO can be released from GFO in the absence of phosphate, but also that phosphate might (or might not) cause bound copper to be released.

An ion exchange resin, like in an RO/DI MUST release an ion to bind another ion.

GFO is much more complex, in terms of the chemistry taking place at the surface, but it is not a swap the way that an ion exchange resin is.

Copper is also extraordinarily complicated in seawater since most or all of it is already bound to organic matter in reef tanks and in the ocean. It is not necessarily just Cu++ ion binding to GFO. It might be some of that. But it also may be the organic complex binding to GFO (or GAC, purigen, etc.)

FWIW, many things will bind to and/or interact with GFO.

No copper in the freshly mixed saltwater, only in the water he is pulling from his system and allows to react with GFO.

 

[Randy Holmes-Farley Verified Community Expert]

No copper in the freshly mixed saltwater, only in the water he is pulling from his system and allows to react with GFO.

I wouldn't be sure the GFO is doing much at all for copper at normal to slightly elevated levels. I've not seen any evidence that it does, but I suppose it may. Dana's experiment (link below) was at super high copper levels and it plateaued (meaning no more lowering of copper) at levels well above what is suitable for a reef tank. Would fresh GFO in that experiment lower it more? Not sure.

https://www.advancedaquarist.com/2012/2/chemistry

Ubnless this was a test for fun, I'd use a known copper binding material such as Cuprisorb, Metasorb, or a Polyfilter.

 

[Reeferdood]

I wouldn't be sure the GFO is doing much at all for copper at normal to slightly elevated levels. I've not seen any evidence that it does, but I suppose it may. Dana's experiment (link below) was at super high copper levels and it plateaued (meaning no more lowering of copper) at levels well above what is suitable for a reef tank. Would fresh GFO in that experiment lower it more? Not sure.

https://www.advancedaquarist.com/2012/2/chemistry

Ubnless this was a test for fun, I'd use a known copper binding material such as Cuprisorb, Metasorb, or a Polyfilter.

Well he is desperately trying to find the source of copper in his system. He has a total of about 3000 gallons, really impressive actually..
I seek advice from you because he is not on the forums to do so himself..
He is a neurosurgeon so he will tinker until he finds a smoking gun and you are the best one to ask.
Thanks again.

 

[Randy Holmes-Farley Verified Community Expert]

Well he is desperately trying to find the source of copper in his system. He has a total of about 3000 gallons, really impressive actually..
I seek advice from you because he is not on the forums to do so himself..
He is a neurosurgeon so he will tinker until he finds a smoking gun and you are the best one to ask.
Thanks again.

How high is it?

Sources of copper could be

1. top off water (0 ppm TDS from RO/DI of drinkable water won't typically be a source, but tap water can be )
2. brass or similar metal fittings on anything in contact with water (including between the end of the DI and the tank).
3. Copper pipes somewhere above the tank or sump that condense moisture and drip
4. Contaminated rock or other things from a different tank where copper was used as a med

 

[Cory]

Also if hes using a pool pump some old ones used brass inside.