Sequestration or Chelation??

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?

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 :eek:, but I think they all seem to work the same :rolleyes:. Maybe Waterbear or Chem Geek will chime in and give us the chemical difference.

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!

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:confused:. 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.

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:D

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.:confused:

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.:)

[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:D
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!:eek:
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.:confused:[
Yup!
/quote]
Isn't chemistry FUN!:eek:

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.:rolleyes:

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. :D

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:confused:. 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:)

Quote:

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Originally Posted by 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.:rolleyes:

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. :D

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:confused:. 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:)

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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.

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.

I have used both sequasol and metal free. They are both good, so it doesn't matter which you use. I would add a good dose right after your fill - a little more than the bottle says. You will not have to do anything else when you close. I have already closed with stains and opened to a stain free pool - I don't know why, I can only guess, so don't worry about adding any sequesterer when you close. I would save the chemicals for next year when you open. Next year when you open, before putting anything else in the water add the sequesterer. This way any metals the were introduced over the winter or with your fill water will be taken care of. Then you only need to add it if you see any stain starting to form. If you see stain start, take your ph down to 7 - 7.2 and add sequesterer - it should lift the stains before they settle. Feel free to ask any questions you have:)

WOW --- this is great information and I do (almost) understand it.

Evan -- I've learned more chemistry since looking at this forum than I did at Brevard Engineering College (now FIT) in Melbourne back in the 60s.

Marie -- Keep the info coming about Metal Magic --- I'd just as soon have it settle so the robot can gobble it up and I can get rid of it. I do add quite a bit of water from the well so I guess the chelator or sequestrant will be a regular around here.

The free Cl has nearly quit dropping (2.8ppm) so I'm still waiting to add the Ascorbic Acid. Since the CYA is ~50 it could take a while based on Richard's half life explanations. Might have to add some sodium thiosulphate to lower it the rest of the way (Target = 1-2ppm)

Marie --- I'll have to look you up next time I make the run from Mahanoy to Shamokin. With all that coal leeche no wonder you get stains.:eek: Do you have to fight low pH too?:eek:

Mahanoy to Shamokin!!! We are neighbors:) Yep, the coal regions. I used to fight low ph, but this year for some reason my ph keeps rising:confused: It may be because it has been dry and I haven't used many trichlor pucks this year. I used to use them to keep the ph low so I wouldn't get stains. This year I didn't have any problem with stains so I have been just using bleach. I didn't check it today, but it probably is low from all the rain. What town are you from?

Quote:

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Originally Posted by 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.

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First thing I would do is get the water tested for metals...if there are non present then don't add either one....If it ain't broken don't fix it!

Stain Free followed up with Metal Free (both Natural Chemistry products) per the directions on the bottle. It was dark till the metal free went in so I don't know if it got cloudy or not. I do know that the stain disappeared almost immediately when the Ascorbic acid hit the water.:)
We'll see the results in the morning.

The jug of Metal Free said to run the pump 72 hours then change DE (in my case) but I'm wondering how long I should keep the Cl down??? It does not say --- with the rain that we are supposed to get, I'm a bit nervous with it down around 1.5 ppm and CYA ~50. Any thoughts?? Phosphates are <100 so there isn't anything for algae to eat.

After 24 hours and if the stain is gone, you can start to balance the water. Your ph and alkalinity will be probably be low after the ascorbic acid, and you will probably have trouble keeping chlorine in the water. You can get your ph up to 7.2 and then start to add the bleach, add enough to take it up about 2ppms, waiting a little while and adding more until you reach about 4 or 5 for your cya. If you start to see stain forming, make sure your ph is no higher than 7.2 and add more metal free. You should be fine. Just don't shock for at least a week, maybe 2. You can keep your chlorine at the high side for your cya which at 50 would be 6-8ppms, but I wouldn't go higher for the 2 weeks. Feel free to ask any questions you have, good luck:)

The pH was ok this morning (7.5) TA down to 90 but FCl was 0.0:eek: Added a bit of 6% (diluted first in pool water) to bring it up to ~1ppm and threw the robot in to keep stuff stirred up. The water is crystal clear and no apparent sediment on the seams of the liner where it always collects.

Still no rain but they are predicting 4-6 inches around here --- We'll see. I want to get CYA down to ~20 for winter then see where it needs to be for operations next year.

I'll keep you posted on the stains removal process.

OK Marie ---- How long should I expect it to take (getting the chlorine back up)??

I've read to bring it up slowly (1ppm per day) but at this rate it'll be next summer:D

Since I did the Ascorbic Acid and the Chelator, I have added Chlorine 8 times, and still the cl is <1ppm after a few hours. I suspect it is still consuming the Ascorbic Acid but after 3 days --- Enough already:(

One good thing --- We had 4.06 inches of rain, so my CYA is now near 40 :) So I should be able to go down a notch on Ben's BG Chart. I'm still shooting for between 4 & 6 just to keep it on the high side.

For those who care:
Water Temp 68 BRRRRRRR:(
pH 7.5 by titration
FC .4 ppm (FAS-DPD)
TC .6 ppm (FAS-DPD)
CC .2 ppm (FAS-DPD)
TA 80 ppm (by titration)
CH 240 ppm (by titration)
Phosphates <50 ppm
CYA = ~43 (turbidimetric)

Yes, the ascorbic acid is eating the chlorine. You can start to raise the chlorine to 6, just lower the ph back down to 7.0 - 7.2. You don't have to raise it so slowly when the ph is down. You should be fine - just keep adding chlorine to take it back to 6. As long as the chlroine is still being eaten, you won't get any stains - it won't be high enough long enough to stain;) You should be ok with the sequesterer. Don't worry so much, I know it's a pain, but you will get the hang of it. If stains do start to come back, just lower the ph and add more sequesterer - it will fade the new stains right away. It is just the embedded ones that need the ascorbic acid. My water temp is 68 too:eek: I am hoping to get some more swim season in, but it doesn't look too good - I get really sad when I have to close the pool:( Keep us posted on your progress.

Rather than leave everyone hanging, Here is the end of this saga. The stain is gone and the pool is back to normal.

It took a total of 6 days to bring the chlorine and pH back into range and keep it there without a lot of extra messing around. I have started using the maintenance dose of Metal Free so hopefully this process will not have to be repeated anytime soon (Never will be too early). So far I do not see anything "falling out" so I suppose it has been captured (hopefully forever).

Other than the cool nights and lack of sunshine, swimming might get back into the near future but the weatherman is not cooperating (65 high tomorrow) :( -- Pool temp is 79 today (my minimum is about 83).:o

Thanks again for the help and Information. This thread gets printed and filed for future reference.

Glad to hear all is well:) Don't worry, if you get any stains back next year, you will know how to get rid of them before they become hard to remove. The key is to keep the water balanced with the ph on the low side, and keep up with the chlorine so you don't have to shock very often. Plus keeping the sequesterer in the water at all times. It is the first thing I put in the water when I open in the spring - sequesterer goes in as soon as the cover comes off - then chlorine. Tomorrow I close the pool, I am sad:(

Hello again,

Well, nearly a year has past and the same stain is back. I have used a chelating agent (Metal Free [Natural Chemistry]) religiously. The pool is sparkling and the Chemistry is great (see below), I just don't understand why this stain keeps coming back??

The pool gets cleaned 3 or 4 times a week with the Aquabot (it's never dirty -- mostly the pool gets cleaned -- because ---) so if something would drop out, it would get gobbled up before it could go (dissolve) back into the water.

Since we are full BBB with bleach injection everything has been very stable, and the water has been great. Not even any good reason to shock.

My only thought was that I do not change the DE filter unless there is a back pressure situation and this has only occurred twice since I opened the pool.

Perhaps I need to change to a sequesterant?? What do you think?? Any recommendations??

H2O Temp = 86
FC = 3.6
CC = 0
CYA = 28
Phosphates <50 PPB
pH = 7.6
TA = 90

This is only a theory on my part. I used to get a lot more staining when my cya was under 40. I now keep my cya at 50 or a little higher. One year I experimented with keeping it at about 30 and had a lot of stains, Last year I kept it at about 50 and had very little staining. The lower cya may make the chlorine eat up the sequestering agent faster. I have been using Proteams Metal Magic, and it seems to work really well. If I see any stain starting to form, I add it and it takes it away. I also have been keeping my ph low - not higher than 7.4, with alkalinity no higher than 90. I also used a clarifier that Waterbear reccommended - Seaklear natural clarifier, here is a link: http://www.poolgeek.com/SeaKlear-Nat...ools-p/skq.htm
I am not sure which it is, or the combination of all three, but my pool has not had much staining at all this year after the initial ascorbic acid treatment I had to do at the beginning of the year after opening to a green swamp and having to have my chlorine levels at shock levels for 2 weeks:rolleyes: I am working with a friend of mine that has had a lot of pool problems, algae and staining:( I am going to try using this theory on her pool too. I will keep you informed.

From your water chemistry, everything seems to be in order. I would try to raise the cya up a bit and see if it helps keep the sequestering agent in the water longer. Maybe even try the SeaKlear. I don't think there is much difference between the good sequestering agents. So it is up to you. I do like the Proteam Metal Magic, but I also liked Jack's Magic and Sequasol too. I have heard good things about getting a metal out from Ace Hardware that is cheaper too. I can't remember the name right now. I would suggest taking the ph down and adding the sequestering agent, to see if that will do the trick by itself. If not, a little ascorbic acid will do it - I know it is a pain, but you may not need a lot. I am still experimenting to see what works best, that is why it's great that you let me know works well for you, so we can put them in the "stain eliminator" reference:)

Hi Marie,

Thanks for the reply. I was looking at the Metal Magic web site, this product seems a lot cheaper than the Natural Chemistry. Just wondering, did you use the SeaKlear because the Metal Magic made things cloudy?

I've been procrastinating since things are finally nice and warm and the stain is still "minor" (not visible except the skimmer boxes & not the steps yet) and I don't want to lose a day of swimming right now. Also, I did not see anything about phosphates on the Metal Magic label either. I'm still investigating.

What bugs me is where this is coming from since the K-1716 Iron Kit from Taylor shows 0 ppm, same with copper using the K-1730 kit (0 ppm) (both samples of my make-up water). What else is there? Or better yet how do I test for it?

All HEDP based seqesterants will cause phosphate levels to rise. Don't worry about the phosphates. It's really a scam. Chitosan based clarifiers (like SeaKlear) have some sequestering abiltiy but not as much as a HEDP based product. The Ace product is O-Ace-Sis Metal Out Plus.

Hi Evan,

Thanks for weighing in. I'll look for a Ace with a pool section. Most everything in my area are TV or Do it Best, but around work there are a few.

Any SWAG why I don't show levels (Metals) when I test my make-up water (K-1716 & K-1730 [both Taylor])??

Thanks Evan:) I am wrinting that name down now. As far as the metals testing in the water, I never have metals, but I get stains. When the metals have fallen out, or are sequestered, the test will not show metals. So, you would have to get it at the perfect time to have the metals show up on the test - unless you test your fill water - that will show metals (if that is where they are coming from). Metals can get in the water in so many ways - If your pool stains, then there is some metal in there that has to be controlled. I'm sorry, I just don't know where your metals are from, and I don't know where my metals come from either:confused: If I ever figure it out I will post - and I hope you do the same:D We can all help each other by posting what works, because every pool is a little different so there are a lot of things to try:)

Evan, what would make the water cloud when you put bleach in it? Today when I added bleach, you can see a cloud forming. The water was clear before the bleach. Could it be the sequestering agent? Would it be that there is too much in my water? The ph was low this morning so I added some borax, then I add some chlorine a little while later. My numbers are:
FC - 7
CC - 0
PH - 7.5
Alk - 100
Cal - 170
CYA - 50

I added about 4oz. of metal magic and 2oz. of SeaKlear on Thursday. The water was a little hazy, but when I added the bleach today, it clouded up. My alkalinity has gone up about 20ppms too. We did have a storm last Sunday (that's why I added the sequestering agent and SeaKlear), and it has been very hot here, so I have had a heavier bathing load. I just can't figure it out, maybe you can help;)

If you have a lot of seqeusterant in the water I suspect that the bleach was oxidizing some metals and the sequesterant reacted with it to form a metal phosphonate precipitate (remember that Metal Magic is supposed to form 'crystals' that your filter willl filter out:rolleyes:). That is about the only thing I can come up with.

I am just stumped:confused: Although it may be algae, my pool used up about 7ppms of chlorine today, which is very high with a cya of 50, the only swimmers were my husband and I, I don't think we have that many cooties:eek:. I just can't fiure out why it clouds with the addition of bleach, using up sequestering agent sounds right, but I really don't think I have too much sequestering agent in it, I will have to test it with the sequestering kit I just got, and have been too busy to look at:D