Sequestration or Chelation??

[Jakebear]

The chemical dictionaries define these as follows:
Sequestration
--The inhibition or prevention of normal ion behavior by combination with added materials, especially the prevention of metallic ion precipitation from solution by formation of a coordination compound with a phosphate.
--To hold (as a metallic ion) in solution especially for the purpose of suppressing undesired chemical or biological activity.

Chelation
--A chemical compound in the form of a heterocyclic ring, containing a metal ion attached by coordinate bonds to at least two nonmetal ions.
--The chemical process that takes place in chelation is complicated, but put in simple terms, the metals, bind to the chelating agent and then are eliminated.

Both definitions reference Ascorbic Acid ---- Are these both the same??

In terms of stain removal, which is better?? What is the product of choice?

[mbar]

In a lot of pool glossary's they say the same thing. Some definitions of sequestering agents say they bind onto the metals to keep them in suspension, and some of the chelators say the same thing. Some of the sequesterers say they will bind with the metals and filter out, some of the chelators say the same thing. Ascorbic acid is supposed to be a chelator, but you have to put in a sequesterer to bind onto the metals once they go back into solutions so that they don't precipitate out again. I have used Metal Free (supposed to be a chelator), Sequasol (supposed to be a sequester), and the directions are the same on both. I have also used Jack's Magic. I just used Metal Magic by proteam today, since we had a lot of rain, and I had to shock the pool. So far they all seem to work the same. Metal Magic is supposed to turn the metals into salts so that they can be filtered out. I let you know if I see any difference.

It is all very confusing , but I think they all seem to work the same . Maybe Waterbear or Chem Geek will chime in and give us the chemical difference.

[waterbear]

Well, I hope I don't confuse you even more....all chelators are sequesterants but not all seqesterants are chelators...chelating compounds have a ring structure (this is just what it sounds like, the atoms are arranged in a ring shape except it is broken and not complete so it can 'clamp' onto the metal ions...sequesterant might or might not have one, but they both will 'deactivate' a metal ion so it does not react with other substances in the water....As far as ascorbic acid...it is actually a reducing agent (this is why vitamin C, ascorbic acid, is referrred to an Anti-Oxidant...the opposite of oxidation is reduction) that changes the oxidation state of metal ions...it does not deactivate them...just makes them dissolve back into solution (It's actually a bit more complicated than that but you really don't want to hear about electron states and orbitals and redox equations ...do you?. (Almost like a line from Wizard of Oz... "electron states and orbitals and redox equations, Oh MY!") Once they have redissolved the sequesterant or chelator added to the water (You did remember to add it, didnt' you?) then deactivates them.

Realize that my explanation is very over simplified but is basically correct. If chem geek or any othe techno geeks care to discuss this with me we can meet in the china shop! This one is for the non technical crowd!

[mbar]

Thanks Evan!! you always make chemistry easier to understand. Most of the products claim to do the same thing - some even claim to "reduce" metals, and some claim that they will filter out. I learned from you, that they are really only sequestered, and stay in the water - unless the product does change the metal so it can fall out in a substance that can be filtered, as the metal magic claims. One of the products I looked at said that ascorbic acid was a chelator, that's where I got that from. It is so hard to believe anything they claim. So I always go back to the experience I have with my own staining. I just tried the metal magic yesterday - so far I don't see any difference. Will keep you posted.

[Jakebear]

Marie -- Evan

Thanks for the info.

The weather has been crappy here in PA so now's the time to do this --- I have a supply of Stain Free and Metal Free (Natural Chemistry). As soon as the CL gets down to between 1 & 2 ppm I'll do my thing. With "Ernesto" coming up the coast we probably won't be swimming anyway (even though there is no restriction).

I was in another Chemical reference book today --- they said the same thing you did Evan so perhaps you use the same book

I still can't get over my 0 iron and copper especially the iron. The Taylor kit doesn't lie --- Even though one of the people I work with had an explanation wanting to know what kind of Iron the test was for???? Since Taylor sells the K-1716 kit for pool water testing I figure it is for the "right kind" of iron.

[mbar]

Today I checked to see if the metal magic did anything. I did see some sediment on the bottom of the pool. The ph was low - I guess that's why metal magic wants the ph to be at 7.5 before you use it. I started at about 7.5 - 7.6, and today it was about 7.1 - I had slight staining in two spots before I put the metal magic in, and they were still there after 24 hours. I do have some ascorbic acid, and since we are having bad weather, I may use it to see if the metal magic will turn the metals that are lifted into the metal salts. My chlorine is at 10ppms, so I won't use any until it comes down - it will just waste it. I do have to say that since I had a lot of new water in the pool, and took my chlorine up to 12, I didn't get anymore stains - so at least the metal magic did work in sequestering, and maybe chelating the metals (the sediment). Jakebear, I live in PA too, so I figure now is the time to experiment with these products , while the weather is bad- I don't have much in staining though. The water is crystal clear, I'll see if it clouds after the ascorbic acid is used. I'll keep you all informed.

[waterbear]

[quote=Jakebear]Marie -- Evan

Thanks for the info.

The weather has been crappy here in PA so now's the time to do this --- I have a supply of Stain Free and Metal Free (Natural Chemistry). As soon as the CL gets down to between 1 & 2 ppm I'll do my thing. With "Ernesto" coming up the coast we probably won't be swimming anyway (even though there is no restriction).

I was in another Chemical reference book today --- they said the same thing you did Evan so perhaps you use the same book
Only reference I used was what was stored in my head....nice validation that the stuff I said was actually correct!
I still can't get over my 0 iron and copper especially the iron.
If you have stains in your pool then you probably no longer have metals dissolved in the water....they are now precipiated out as stains. The ascorbic acid (or other reducing agent) will cause the stain to convert to a form that will dissolve back into the water (It changes the oxidation state)....and the stain vanishes but now there are metals in the water! This is where the sequesterant comes in.

FYI, NaturalChemistry's Metal Free is a chelating agent (EDTA) while Proteam's Metal Magic (HEDP, a phosphonic acid derivative) is a seqesterant. EDTA has a ring structure HEDP does not.
To confuse matters even more, sequesterants are measured in how well they seqester a particular metal by their "chelation index" for that metal!
The Taylor kit doesn't lie --- Even though one of the people I work with had an explanation wanting to know what kind of Iron the test was for????
The Taylor test uses Tripyridyl-s-triazine which tests for Fe(II)...Fe is the Chemical symbol for iron. The (II) refers to it's oxidation state.
There ARE different oxidation states of iron, Fe(II) and Fe(III).
Since Taylor sells the K-1716 kit for pool water testing I figure it is for the "right kind" of iron.[
Yup!
/quote]
Isn't chemistry FUN!

[mbar]

Thanks again Evan! Now I see why metal magic will not take the stains off the surface of the pool - which it says it will. The only way that the metal magic will take the stains off somewhat is the same reason that taking the ph down to 7 and then putting in a sequesterer will work. The metal magic takes the ph down on it's own. Therefore, if the stain is there for a long time (more embeded) then you will need ascorbic acid or some other reducer to remove the stain from the surface of the pool and then any sequesterer will work. The only thing that the metal magic claims that would be different is if it really does turn the soluable metals into metal salts so they can be filtered out.

To say this is confusing is an understatement! I know what has worked, through my own experimenting on my pool, but now you are giving me the background to understanding why.

Let's see if I have this right:
You need a reducing agent (like ascorbic acid) to take the metals off the surface of the pool, putting them back into solution so they can be sequestered.

Then you need a sequestering agent or a chelator to bind with the metal to keep it in solution.
Metal sequesteres and chelators, even though they are doing different things, are acting the same way as far as the metals in the pool are concerned. Neither one is actually taking the metals out of the water.
The only way to get the metals out of the water without them staining is to find something that will turn the metals into a solid form that can be filtered out. This is what Metal Magic is claiming to do.

I am going to try my experiment with the ascorbic acid to see if the removed stain - I never thought I would say I wish I had more stain! - will get turned into metal salt with the metal magic that is in the water, so it can be filtered out.

This morning there was some more sediment in the bottome of the pool - hopefully it is the metal magic working to change the metals that are in solution into metal salts so they can be filtered out, or vacuumed out.

I will try this again in the spring when I open the pool. It will be easier to test if I let some stains form, but it will worth it to find out how to get the metal out!

I will keep you all posted

[waterbear]

Thanks again Evan! Now I see why metal magic will not take the stains off the surface of the pool - which it says it will. The only way that the metal magic will take the stains off somewhat is the same reason that taking the ph down to 7 and then putting in a sequesterer will work. The metal magic takes the ph down on it's own. Therefore, if the stain is there for a long time (more embeded) then you will need ascorbic acid or some other reducer to remove the stain from the surface of the pool and then any sequesterer will work. The only thing that the metal magic claims that would be different is if it really does turn the soluable metals into metal salts so they can be filtered out.

To say this is confusing is an understatement! I know what has worked, through my own experimenting on my pool, but now you are giving me the background to understanding why.

Let's see if I have this right:
You need a reducing agent (like ascorbic acid) to take the metals off the surface of the pool, putting them back into solution so they can be sequestered.

Then you need a sequestering agent or a chelator to bind with the metal to keep it in solution.
Metal sequesteres and chelators, even though they are doing different things, are acting the same way as far as the metals in the pool are concerned. Neither one is actually taking the metals out of the water.
The only way to get the metals out of the water without them staining is to find something that will turn the metals into a solid form that can be filtered out. This is what Metal Magic is claiming to do.

I am going to try my experiment with the ascorbic acid to see if the removed stain - I never thought I would say I wish I had more stain! - will get turned into metal salt with the metal magic that is in the water, so it can be filtered out.

This morning there was some more sediment in the bottome of the pool - hopefully it is the metal magic working to change the metals that are in solution into metal salts so they can be filtered out, or vacuumed out.

I will try this again in the spring when I open the pool. It will be easier to test if I let some stains form, but it will worth it to find out how to get the metal out!

I will keep you all posted

To the best of my understandintg you have it right! As far as Metal Magic goes....they might have a reducing agent in it as well as a seqesterant. Can't tell from the MSDS.

[doggie]

I hope nobody minds me butting in here. I was wondering which would be a better product to use to remove any potential metals from my fill water when we refill after the new liner is installed. I have some of both GLB's Sequa-Sol and also Natural Chemistry's Metal Free.

Would one be better than the other on a fresh fill? Or should I use them both before I close for the winter? (not at once of course)

I want to make sure and get all the metals before they have a chance to do anything. I don't know the metal content, but it seems most of your opinions is more is better when it comes to preventing metal stains. This will be city water by the way.


Thanks.