does copper really bind to glass?

[pstolfo]

Just curious if copper really binds to glass and silicon. I've used tanks that had been treated with copper in the past and have yet to have a problem. Just looking for a chemist's opinion.

[Gamera]

As you want a chemists opinion, I'll add my two cents before Randy does. I'm uncertain if he'd agree with me, but here's what I think off the top of my head:

Yes.

Copper can bind to glass.

As the only forms of copper I'm used to working with are either Cu(II) and Cu(I) (ironic in that I go to CU, but there's also a CU in Denver...), I'm inclined to say that the answer is a wholehearted yes, but that chelation of copper by hydroxylated silicate species is most likely not the main method of removal of copper in a marine system.

On the other hand, the lability of SiO ligands is questionable. I know that water tends to be quite labile as a ligand, but that the addition of silicon to oxygen dramatically changes oxygen's inherent reactivity.

What does this mean?

(1) Lability (for the non-chemist) is really a function of how well something binds to the metal. The more labile, the less likely it is to bind and stay there for longer periods of time. If oxidized species of silicon are indeed less labile than water (at the business end for both), then I would presume that copper would find a comfortable home at the interface. There is precedence for this type of chemistry (at least) in the form of metallic deposition onto hydroxylated surfaces in the preparation of monolayers (just trust me when I say it's been done before :p ). Whether or not that type of chemistry is applicable, I can't say for certain, but it does bear a great deal of similarities at the surface (no pun intended).

(2) Get an inorganic chemist. I'm an organic chemist, so my experience with inorganic chemistry is limited. Take my advice/replies with a large grain of salt.

I'm in the process of waiting for a reply from a friend that is an inorganic chemist on this topic. I'll get back with his answer.

[Randy Holmes-Farley]

Gamera:

I'm always glad to get the input of other chemists, such as yourself and your friend. I'm looking forward to what he has to say!

pstolfo:

When someone asks "can it bind", the answer almost always is yes, regardless of the specifics of the question!

Then, one needs to think about how much binding might be significant to the person asking the question.

In the context of treating a fish in a quarantine tank, the glass apparently doesn't bind enough to be significant. I base this on the fact that people can easily attain stable levels of copper in a glass tank, and that one cannot so readily attain such stable levels in a tank containing calcium carbonate sand (which will bind substantially more copper as it can readily displace calcium in the crystal). In general, it is the calcium carbonate that is a much bigger problem than the glass in tank configurations.

In the context of toxicity of the tank itself after simple rinsing after use as a quarantine tank, it depends on a lot of factors. Ron has some experience in cleaning glass to remove copper, so you might also direct this question to him. As I recall from his comments, it can be done, but it takes a fair amount of work to get copper low enough so that it absolutely isn't an issue for any inverts.

Now some general copper chemistry:

Copper (as copper I or copper II) does bind to oxygen-containing species like silica. Copper in a reef tank will be only copper II (Cu++), except in anaerobic regions, so that's what we should focus on. Without doubt some copper will bind to the SiO- and SiOH species on the surface of the glass. In an application where you also have calcium carbonate rock and sand, glass binding can probably be ignored as being much smaller.

Silicone is another story. I don't believe that enough copper ion will absord into or adsorb onto silicone to be important in an aquarium application. However, some people use various forms of "chelated" copper. Depending upon what organic chelator is used, this species may be substantially more hydrophobic than bare Cu++, and it may absorb onto the silicone to some extent. Also, bare copper may chelate itself to organics in the tank, and these may bind to the silicone. Overall, however, I don't believe that silicone binding will be as great as glass binding, and can probably be ignored by aquarists.

I think different people have different thresholds for saying whether something is OK or not. If you have successfully reused copper-treated glass tanks for inverts, then I'd say don't worry too much about it. The copper coming off the glass and getting into the water may not be enough to be important to the organisms that you want to keep.

The water tests that Ron is running may give us a better handle on how much copper is typically in our tanks, and will give us a benchmark to think about. I know from at least one participant that he has copper levels 100x seawater, and doesn't apparently have a problem (at least that he's noticed). Consequently, I don't have a good handle on how much copper is OK, and find it hard to answer what procedures might be OK, and what ones might not.

[Gamera]

The reply from the inorganic chemist is that copper shouldn't bind in any significant quantity to hydroxylated silicates.

[Randy Holmes-Farley]

Gamera:

Thanks.

Personally, I expect that his answer is based on the fact that copper binds other things more strongly. In this application, however, it may not take much binding to be problematic. Many chemists just don't think of ppb levels as being significant. However, I'm certainly open to the possibility that some people may have exaggerated the concern in the past.

I see from your profile that you are studying liquid crystals. Care to tempt us with some details?

[Gamera]

Randy -

Sure thing. It's not really reef chemistry related (though I did start off as a natural products/hardcore synthetic chemist), but you asked, so I guess I'll try to describe what I'm doing...:D

Liquid crystals, like the name implies, is a state of matter that is neither purely liquid or purely crystalline. It's best thought of as a liquid with one or more degrees of long range positional order, up to, but not including three dimensions. There are 'soft crystals' that have short range order in the third dimension, but no long range order in that dimension, but that's a nit-picky detail.

Materials that display liquid crytallinity are pretty fascinating. They also make for great displays and telecom switches, among other things. However, there's a fairly large dearth of information regarding their behavior that isn't at an empirical level, mainly because the field is relatively new (my particular subset of LC chemistry is only 6 or so years old). That's not to say people in the field aren't making advances.

There are a multitude of reasons industrially why we want to study these things. They're all pretty obvious. Academically, it's along the lines of looking for new phases of matter (since that's what they really are). Theoretically, there could be an infinite numberof phases, and (in my opinion) matter really should be viewed as a continuum rather than quantized (take that p-chemists :p ).

I won't go into the details of my particular field of LC chemistry. Needless to say it boggles the mind. Suffice it to say that life as we know it is typically based on molecules that have a handedness (ie - chiral). Typically, an ensemble of chiral materials in nature leads to a chiral 'macromolecule.' In other words, there's an energetic preference to be 'left' or 'right' handed if you start from left or right handed molecules. Oddly enough, with the liquid crystals I study, you can take chiral materials and get no preference to be one way or another, or start from materials that have no handedness and prefer to be one way or the other. Again, it's best to simply state that as a chemist, it's extraordinarily disturbing.

However, I've been also starting to research an associated field of liquid crystals that deals with biological systems that create liquid crystals, and then lock them into macrostructures that are no longer liquid crystals, but function like liquid crystal cells. It's quite fascinating. Jeweled scarabs are a classic example. The more research that's done, the more species people are finding that use this as a means of differentiated communication based on region, as different regions will lead to different growth patterns - and therefore different optical activity.

That's basically it. In a nutshell.

As another chemist (or at least, recognized chemist on the way), I'll be trying to put my two cents in here as well. If nothing else, just to keep Randy honest. :p

[rshimek]

Hi,

As a tangent to this, I would like to explain why I have a significant "distrust" of much copper in tanks - and why this water study may be interesting in that regard.

About 10 years ago I was the head honcho of the marine biology section of an engineering consulting firm in the Puget Sound region. We specialized in remediating highly political, very nasty environmental disasters (read this as: superfund sites).

We used a number of different tests to examine various sediments, pollutants, etc. in the real world and to note their effects. One set of these tests were bioassays - particularly we usually tested 3 types of animals for acute and chronic reactions to the chemicals. The animals were sediment burying amphipods, sea urchin larvae, and polychaete annelids (aka "bristle worms').

We tested a lot of sediments that contained a large number of metals - arsenic, copper, iron, zinc, silver, and mercury were the "biggies."

After running the bioassays we found that we could clean all of the other metals out of our aquaria pretty easily (or at least my techs could) If we had sediments high in mercury for example, and ran a test with them, we could clean the system easily enough and thoroughly enough that a subsequent test would not show any effects. However, if we ran the test with either a diluted copper compound or sediments containing copper, any further tests using that aquarium were compromised and would give increased mortality. We sent a couple of sample aquaria to another research institute (one of the Battelle labs, I think) to see what was the problem, and they came back and told us it was "adsorbed" copper.

The concentrations of copper in these tests were sometimes quite low, only margninally above ambient sea water, but still often caused problems within some of the bioassays - primarily the larvae.

So... I got a good healthy distrust of any excess copper.

Now.... how this will all shake out in light of the water sample results, I don't know. High concentrations of copper may be (and probably are) tolerable to some animals. Yet, at the same time copper is a very potent molluscicide and even in small concentations will effect larvae. In effect, high concentrations of copper in our tanks may be "filtering" our animals...

More to come, I suppose, pending my analyses of the results of the water study.

[Gamera]

While this may or may not be applicable, or even viable, it was recommended as a possible test to take tanks that were treated with copper, 'clean out' the tank to eliminate as much copper as possible (via water changes, what have you), and then rinse out the tank with a health dose of methanol.

The methanol from the rinse can then be run through either ICP-AA or electrospray to try to quantify the actual concentrations.

I'm sure this is already being done, but I just thought I'd add it here.

I honestly don't think that copper stays very long in the aquarium given enough water changes (though I'm sure this will be pointed out as being highly subjective with regards to how many is 'enough'). I could easily be wrong.

I won't argue that copper is a potent toxin. In terms of a biochemical agent, copper is extremely potent in my experience. However, I will argue that copper stays resident in the tank to a significant degree in terms of a measurable concentration. Ppb? I can see that being significant.

But, naturally, I'm a chemist and not a biologist. I don't even know what Ld numbers are for copper toxicity.

However, just as a point of interest for me, I'd like to know what's going on biochemically with the copper in tanks that results in invertebrate death and only stress in larger fish. Is this simply an argument of overall concentrations over varying system sizes?

[Randy Holmes-Farley]

Thanks again for the input Ron. I knew we could keep you busy here as well! I recalled your experience about copper , but didn't remember enough details to give to others.

<< Now.... how this will all shake out in light of the water sample results, I don't know. High concentrations of copper may be (and probably are) tolerable to some animals. Yet, at the same time copper is a very potent molluscicide and even in small concentations will effect larvae. In effect, high concentrations of copper in our tanks may be "filtering" our animals... >>

In Spotte's "Captive Seawater Fishes" he goes into detail on how copper is toxic, and makes the claim that for many inverts (but not all) it is the free copper (Cu++ not bound to an organic, but certainly complexed to other inorganics like CO3--) that is most toxic.

My thought is that since our tanks have far greater concentrations of organics than seawater, we may be able to bind up the copper in the organics in ways that are substantially less toxic than free copper. The only exception Spotte gave were some species that pulled in copper with the organics. So maybe we select out some, as you suggest, but perhaps not all.

Gamera:

<< I'd like to know what's going on biochemically with the copper in tanks that results in invertebrate death and only stress in larger fish. >>

As I mentioned above, Spotte has an extensive discussion of this. I'll check it later and give more detail if you don't have that book, but one of the pathways involved zinc, with copper actually causing a release of zinc that itself was the real toxin. In general, he makes the claim that copper is substituting for other ions in certain reactions, but I don't recall which, if he even mentioned them specifically.

[Randy Holmes-Farley]

Gamera:

<< It's not really reef chemistry related (though I did start off as a natural products/hardcore synthetic chemist), but you asked, so I guess I'll try to describe what I'm doing... >>

I think it's interesting for others to know people's experiences even if only tangentially related. Thanks for posting it.

I have some small experience with biological liquid crystals, but in our case we are stimulating them to form in vivo. Unfortunately, I'm not sure whether we have made that aspect of that program public, so I can't go into it any further without checking.


<< I'll be trying to put my two cents in here as well. If nothing else, just to keep Randy honest. >>

The more the merrier!

[Gamera]

Unfortunately, I really only have academic texts with me (and even then, primarily organic chemistry texts - though I do have a good number of biochemistry texts laying around somewhere). I tend to rely on Abel, Fry & Jencks for biochemistry as it typically presents biochemistry from the chemists viewpoint. Unfortunately, again, the emphasis on this text is in secondary metabolites. I really don't own any texts on marine biology/chemistry as I don't have ready access to purchase them. Not to mention, most academic texts are (as I'm sure you know) notoriously expensive.

With regards to the liquid crystals you're working on, while I'm sure it's not possible to discuss them in the forum, feel free to email me if you wish to discuss them. I'm also not able to freely discuss the details of my projects, pet or not, to avoid risking the possibility of having someone else grab the idea and farm it for their own publication. Paranoid, yes. However, as a doctoral candidate it's fairly clear that I need to 'publish or die' as the saying goes. Unfortunate, but a necessity given the competitive nature of the institution and field I'm working in.

Given what you mentioned already, I'm guessing you're working in cholesterics or lyotropics. I'm sure most people don't know what those terms mean, or would bother looking them up, so I should be safe throwing around either term. :D

I'm guessing if we discussed our research here in as specific a means possible we could sufficiently obfuscate what we're discussing to be safe. :p