Ion exchange column chromatography

[Gern]

Hello,
I just stumbled across this forum while I was looking online for some information and thought I would ask a question.

I am currently trying to purify Cu from a solution containing Ga, Co, Au, and large (relatively) amounts of Zn. The final product has to be EXTREMELY pure Cu, like .13ppm all other metals.

I am not sure if this is the sort of thing discussed on this board as most posts seem to be about HPLC type equipment.

I will provide further details if there is someone with experience or willing to help with this problem.

[tom jupille]

What's the question?

[Bill Tindall]

I'm going to assume the question is how to purify and that answer would be electrodeposition of the copper.

[Gern]

The question is how to purify the Cu, so you remove all other metals.

Bill, we have looked at electrodeposition, however the problem we run into is that we have a solution with 500+mg Zn, and barely a microgram of copper at the most.

In looking at papers involving the electrodeposition of Cu from a solution such as this, they have noticed decreasing yeilds as your Zn concentration went up, and ours is way off the charts.

What we have done so far is used an AG50W resin to remove the Ga, and an AG1 resin to remove the Zn. While we get about a 99% separation of Zn doing this, we need to get a better result, without loss of copper along the way. We also have a problem of large volumes due to the column size needed to contain the Zn.

What I would really like is a resin/column that was selective for Cu, and would let the Zn pass through. It is a much easier seraration that way, but I have not been able to find something to do that with.

Other options we have explored are precipitating the Zn to remove the bulk of it, but we have not found a good way to do that yet either.

We can use any chelating agent we would like, so long as it can be removed completely. We can add anything we want basically, as long as we can also remove it.

Ideally, I am looking for a process, that is short, produces a small volume (1-5mL), and leaves the Zn in one place (we need to get it back after the Cu is removed).

[Uwe Neue]

You might be able to do this with a resin containing amino groups that complex the copper specifically.

[Gern]

Uwe, can you point me to some information on that type of separation? I have no experience with it.

Thanks,

Gern

(Edit)I have just found an interesting resin (Dowex M4195) that I think might be able to help with this. Has anyone here ever used it?

[Bill Tindall]

Adjust pH and dump out copper as sulfide along with what ever else comes down. You might even need to add something to come down with the copper so what comes down is enough to see and handle. this step removes all the copper from essentially all the zinc. Then in step 2 do a second purification, electrodeposition or other.

I am curious as to why one would need to do this separation.

[Gern]

Bill,

The reason I need to do this separation is because I work in the radiochemical industry. Zn is our starting material, Cu is the product, Ga and Co are biproducts of the reaction.

The process is to separate the two, while retaining as close to 100% of each. The Zn starting material is over $10,000 per gram, and any Cu we lose, is loss of product.

The nature of the chemicals involved also limit our process. Columns are greatly prefered because pump systems, vaccum and pressure can be used to move the liquid and require little or no contact to the operator. We like to keep everything in a closed system to provide as little opportunity for spilling as possible. Manipulator arms are less than graceful.

I am curious about your precipitation suggestion though. Will Zinc sulfide not come down as well? Also, what assumptions are you making about the solution itself (All metals are in Conc HCl)?

[Uwe Neue]

Considering your task, an enrichment with a suitable amino-phase is probably at least part of the solution. Copper is retained strongly on any resin that contains amino groups. The complexation is favored in the neutral to mildly alkaline pH range. I recommend a clean organic resin to do this. (There are plenty of silica-based amino packings around, but the stability of the bond is not very good.)

If you call me tomorrow at 508-482-2157 and we can discuss some possible solutions. Or you can contact me at my work e-mail Uwe_Neue@Waters.com.

(PS, I am not trying to sell you something. This is not the point. But I may have a solution for you.)

[Mark Tracy]

Dionex makes a couple of columns you might want to look at: CS5A is a low-capacity analytical column, and the MFC-1 is a high-capacity metal-trapping column. You can search www.dionex.com for those products. I don't think we ever tried what you want, but there might be a some good ideas there.

The CS5A separates the metals in the form of their oxalate complexes. With this scheme, copper elutes ahead of zinc by a wide margin.

[Uwe Neue]

I checked on the product that I thought might be suitable. It is a high-purity sample preparation product, the Oasis WCX. It contains a cyclic diamine, which I believe will be ideal for collecting the copper.

[Gern]

Uwe, thanks for that suggestion.

I have ordered the M4195 that I mentioned earlier and will do some testing with it next week. I started pulling information on the Oasis WCX as well.

Jesse

[Uwe Neue]

Sometimes I think I am daft... I was talking about the Oasis WAX - weak anion exchanger. The WCX (weak cation exchanger) does of course NOT contain the diamine, while the WAX does...

Sorry!

[Bill Tindall]

Copper sulfide will precipitate from acidic solution while zinc will not. Also copper will precipitate from a basic solution while zinc will remain in solution. But I can see that ion exchange will be easier to automate. I

I alsoam quite sure you can make a copper complex that will be extractable in organic solvent, leaving zinc behind.

[HW Mueller]

Gern, it would be quite interesting for me to be informed of the activities, halflifes, and concentrations of your isotopes, and of course, how you finally solve the problem. For short halflife species the handled concentrations are so low that the addition of cold isotope (carrier) is sometimes required. In other words, conventional chemistry can often not be applied, especially gravitational methods. So my expectation would be that you would have to go with adsorptive methods. ie, chromatography as some suggested, unless you have mg amounts or more. Or maybe you can devise some surface chemistry, akin to Bill´s electrodeposition??