lanthanum chloride question

[mikesin]

Hello, how does lanthanum chloride work when treating 50lbs of dry rock in a bin of 15 gallons of saltwater? does it bind phosphate that is in the water column only? does it bind phosphate that is in the rock only to release phosphate at a later date? My concern with using seaklear as a phosphate remover is could the phosphate be released at a later date because it has bound to the rock? Is that a valid concern? I have read so many threads on phosphate and lanthanum chloride that I am getting confused. seems I remember reading that low PH causes bound phosphate to become unbound?
i am in the 4th week of trying to remove phosphate from dry BRS rock. I have not cycled yet as i want the phosphate low before cycling. RO/DI water was used for week one, saltwater is now being used. The rocks are removed every 2 days, rinsed with RO/DI water and placed back into new salt water. Phosphates have come down from .45 (hanna checker) to .28 on day two of my rock washing schedule.

[Randy Holmes-Farley]

Phosphate on the surface layers of rock can equilibrate between the water and the rock surface. Lanthanum, like GFO, will bind to phosphate in the water. It then precipitated as lanthanum phosphate and will settle out somewhere. What happens to that lanthanum phosphate over time is not clear.

[mikesin]

Originally Posted by Randy Holmes-Farley

Phosphate on the surface layers of rock can equilibrate between the water and the rock surface. Lanthanum, like GFO, will bind to phosphate in the water. It then precipitated as lanthanum phosphate and will settle out somewhere. What happens to that lanthanum phosphate over time is not clear.

So, rinsing the rocks to remove any precipitate is a must, but then there could be a concern with phosphate that is on the surface of the rock?
Not knowing much about chemistry, I invision phosphate on the surface of the rock, Lanthanum binds to it. then possibly at a later date, unbinds creating a food source for algae. if this is true, a scenario could be once the rock is in th DT, localized low ph could wreck havoc.

[Randy Holmes-Farley]

I don't think it likely that lanthanum will bind all that much to phosphate on the rock, because that phosphate is already bound to calcium. Essentially you are hoping to swap calcium phosphate attached to the rock for lanthanum phosphate that is loose.

[mikesin]

Thanks for the response Randy. I feel a little better using seaklear in a controlled environment such as the tub being used to cure the rock. I'll just make sure the precipitated lanthanum phosphate is rinsed from the rocks before they are added to the DT.

[gpx1200]

i have read a few threads that recomend driping the lanthanum into a filter sock slowly, aparently it will act quickly bonding with the phos inside the sock and the parcipatate is cought in the sock.
i recently added 20lbs of pukani rock to my dt before i knew about the phos, it took about a day and a half for the alge to explode, luckily most of my corals are stuffed into my other tank while i reaquascaped this one so i can leave the main lights off while the calurpa in my sump eats up the phos but this is taking to long so after doing some alittle to late reaserch i'm going to pick up a filter sock and try the seaclear, i plan to put about 30 gals of my tank water into my water change barel with a pump to circulate it and drip the seaclear into the sock, after giving some time for the reaction to finish ill put a filter sock over my pump and return the water to the tank, also thinking of runing a skimmer or carbon in the barel for a while before returning the water to the tank.

[Randy Holmes-Farley]

Yes, in a reef environment, using it upstream from a particulate filter is a preferred method.

[mikesin]

I would do the same and use a filter sock IF I was reusing the water treated with seaklear. Since i am not reusing the water I am simply dripping it in to the bin. Good luck.

[banzai75x]

Do you have to drip it into a outside bin or can you just add it in a larger dose?

Also, lets say I do a dose.. Water gets cloudy.. Wait 24 hours... Can I add another dose or do I have to change out the water in the bin before doing another dose?

[Randy Holmes-Farley]

There's no need to change the water, IMO.

The one concern with this "method" is that the rock may be getting coated with lanthanum, and it isn't clear to me that all of the phosphate will be removed.

[banzai75x]

Originally Posted by Randy Holmes-Farley

There's no need to change the water, IMO.

The one concern with this "method" is that the rock may be getting coated with lanthanum, and it isn't clear to me that all of the phosphate will be removed.

Would I be able to simply rinse off the lanthanum?

I was thinking that as the phosphate leaches out of the rock and binds to the lanthanum, then more phosphate would continually leach out until we get it all out.

Then I could simply rinse off the precipitate from the rocks using a fresh batch of saltwater/rodi.

My rocks are in the display tank now but I don't have many corals/fish and was going to do this in 2 batches. Half the rock and then the other half.

[tmz]

It worked for me a few times for PO4 leaching rock at about 15ml of 40% seaklear in ro water per day to a 20gallon curing bin of saltwter and rock,dosed at once. After a couple of weeks no further leaching was evident on tests. When testing be sure the particulates are settled and don't pollute the sample.

In a living reef tank, fine filtering out the particulates and slow dosing are much more important than in a curing set up,imo.

[Randy Holmes-Farley]

Some of the lanthanum may become incorporated into a surface layer, the way magnesium does from seawater onto pure CaCO3 surfaces. That is perhaps not a big deal (not sure), but it may trap the phosphate under and within it.

[mikesin]

I am hoping that it does not incorporate into a surface layer of the rock. This process is taking quite sometime. Lots of phosphate on this once dryrock.

[Randy Holmes-Farley]

OK, good luck.

[Dr. X]

There are posts regarding cleaning base rock with muriatic acid. The purportedly dissolves the surface of the rock, and so perhaps removes the Phosphate bound to the rock? What do you think, Randy?

I'm also wondering if I can keep the dry rock I am "cooking" by using lanthanum chloride in RO/DI water. Not sure if lanthanum binds phosphate in RO/DI water. Thoughts? With time, the dry rock may increase the pH of the fresh water, though this would likely take months... I'm just looking to save on the cost of salt.

[dkeller_nc]

This is quite an old thread, but I might be able to answer your question.

With regards to hydrochloric acid treatment of dry rock, there are few things to consider:

1) If the "dry rock" has recently been in the ocean, such as BRS's "Pukani", then there's a definite possibility that the outer surface of the rock has a lot of residual dead things on it. So treatment with hydrochloric acid would have a reasonable shot at knocking down leachable phsophates. Note: whether or not hydrochloric acid will dissolve aragonite or calcite rock isn't theoretical - it definitely will, and violently if the acid is concentrated enough.

2) If the "dry rock" is so-called "Reef Saver" rock, it's fossilized material dug up from a land-based quarry and pressure-washed to open up its structure. In this case, it's highly unlikely that any phosphate that it contains is concentrated at the rock's surface. So dissolving the outer most layers with hydrochloric acid doesn't make much sense, as the newly-exposed surface would likely have just as much (or little) phosphate as the original surface.

Regarding Lanthanum phosphate's solubility in water - it will make little to no difference whether you're using RODI or seawater. Either way, Lanthanum phosphate is incredibly insoluble in water of any reasonable pH, and you would need a strong acid to break the La-PO4 bond.

Having said this, though, if your rock is the terrestrial fossilized material, Lanthanum treatment is unlikely to make much difference for the same reason as noted above for hydrochloric acid. In theory, it might be possible to deplete just the very outer layer of the rock of phosphate using a phosphate-specific binding agent such as Lanthanum. But in practice, the problem is that the phosphate on the surface would already be in an insoluble calcium phosphate form. So for the Lanthanum to remove it , the calcium phosphate would need to dissolve into the water, then get precipitated as lanthanum phosphate.

Because calcium phosphate is so insoluble in water, and the kinetics of its dissolution are slow, you might be waiting a very long time for the phosphate to dissolve from the outer layer of rock to then be precipitated by Lanthanum.

[tmz]

I agree, lanthanum and fresh water is ok for dry rock from the ocean . I use saltwater to get the bacterial seeding process going and to use the time involved to help process out organics the rock may be holding as well .

[geomarq]

I have about 100 pounds of dry rock setup in my new DT.. no fish.. took phosphates this weekend from 1.2 to .02 with lanthanum. Going to monitor and see if rock continues to release po4, but I hope I cut some time before the tank is mature enough for fish and corals. Only seen one lanthanum reactor online for $400, seems pricey, but hopefully other companies will continue to research it's effects and provide competitive reactor prices.

[Dr. X]

Originally Posted by dkeller_nc

This is quite an old thread, but I might be able to answer your question.

With regards to hydrochloric acid treatment of dry rock, there are few things to consider:

1) If the "dry rock" has recently been in the ocean, such as BRS's "Pukani", then there's a definite possibility that the outer surface of the rock has a lot of residual dead things on it. So treatment with hydrochloric acid would have a reasonable shot at knocking down leachable phsophates. Note: whether or not hydrochloric acid will dissolve aragonite or calcite rock isn't theoretical - it definitely will, and violently if the acid is concentrated enough.

2) If the "dry rock" is so-called "Reef Saver" rock, it's fossilized material dug up from a land-based quarry and pressure-washed to open up its structure. In this case, it's highly unlikely that any phosphate that it contains is concentrated at the rock's surface. So dissolving the outer most layers with hydrochloric acid doesn't make much sense, as the newly-exposed surface would likely have just as much (or little) phosphate as the original surface.

Regarding Lanthanum phosphate's solubility in water - it will make little to no difference whether you're using RODI or seawater. Either way, Lanthanum phosphate is incredibly insoluble in water of any reasonable pH, and you would need a strong acid to break the La-PO4 bond.

Having said this, though, if your rock is the terrestrial fossilized material, Lanthanum treatment is unlikely to make much difference for the same reason as noted above for hydrochloric acid. In theory, it might be possible to deplete just the very outer layer of the rock of phosphate using a phosphate-specific binding agent such as Lanthanum. But in practice, the problem is that the phosphate on the surface would already be in an insoluble calcium phosphate form. So for the Lanthanum to remove it , the calcium phosphate would need to dissolve into the water, then get precipitated as lanthanum phosphate.

Because calcium phosphate is so insoluble in water, and the kinetics of its dissolution are slow, you might be waiting a very long time for the phosphate to dissolve from the outer layer of rock to then be precipitated by Lanthanum.

Extremely helpful and uncommonly available information. I'm not sure what my "rock" is made of, honestly. I wonder how may of us truly do.
Most of my rock is likely man-made, aragonite-based, bought dry from LFS. Fairly inert, I think.

The hair algae and cyano-magnets in my tank are the clean coral skeletons I bought from another reefer. Clean, dry, and probably full of phosphate. I say probably because I did not previously cook my rock and now am trying to figure out what the source the phosphorus in my tank is. Perhaps it's the crushed coral substrate, though the cyano does not like to grow on it.

In any case, with very little bioload (five fish less than two inches in a 150gal tank), my dissolved phosphorus level is ~0.1 despite regular use of Lanthanum chloride (I built my own reactor). Yes, the lanthanum decreased the phosphorus by half initially, and then drops it somewhat lower each time, but then it slowly rises again.

I'm now removing some of my rocks and trying to see if they are leeching out PO4, in RO/DI. I'm also buying other dry rock and doing the same. Your answer certainly helped, and I will continue to use RO/DI and test the water the rock is in. I'm experimenting, honestly. I will try muriatic acid with some, lanthanum with others. I may even need to remove the substrate (not all at once), if all else fails.

Thanks again for your help.

[slief]

If it were me, I'd use it just like I do when I treat my tank. That way there is no precipitant left in the water or on the rocks and I could measure the results. I'd have constant circulation in the holding bin and slow drip measured amounts of lanthanum diluted into RODI water into filter socks that have water circulating through them. I think it's one of those things that is going to have to be done daily over the course of weeks to effectively remove embedded PO4 from the rocks for the long term.

[Dr. X]

Originally Posted by slief

If it were me, I'd use it just like I do when I treat my tank. That way there is no precipitant left in the water or on the rocks and I could measure the results. I'd have constant circulation in the holding bin and slow drip measured amounts of lanthanum diluted into RODI water into filter socks that have water circulating through them. I think it's one of those things that is going to have to be done daily over the course of weeks to effectively remove embedded PO4 from the rocks for the long term.

Thanks slief. Unfortunately, that's exactly what I've been doing, for a couple of months.

I had a large infusion of phosphate into the system about 6 months off, and am hopeful that you're right - that at some point the calcium-bound phosphate in the rocks and substrate will be removed from the system via my lanthanum chloride reactor. I'm not sure that's where the phosphate is coming from, but I'm operating on the assumption that the phosphate is surface-bound and not part of the man-made rock itself.

As dkeller_nc pointed out:
"Because calcium phosphate is so insoluble in water, and the kinetics of its dissolution are slow, you might be waiting a very long time for the phosphate to dissolve from the outer layer of rock to then be precipitated by Lanthanum."
That's why hydrochloric acid would be a shortcut if the phosphate seems like a worthwhile endeavor-if done right it strips the outer layer of the rock itself.

Thanks to all of you who are more educated in these topics. Randy, I don't think many know about the magnesium-calcium issue, which may be relevant to those who are trying to rid themselves of surface-bound undesirable organisms by raising magnesium to very high levels.

[Dr. X]

This hobby is so frustrating, yet so interesting. The story above reinforces for me one of the tenets espoused by those with knowledge and experience: if you don't want undesirable organisms, you must quarantine. "Cooking" dry rock is one of those things I did not think of as quarantine, but it seems to be.

[Dr. X]

Originally Posted by tmz

I agree, lanthanum and fresh water is ok for dry rock from the ocean . I use saltwater to get the bacterial seeding process going and to use the time involved to help process out organics the rock may be holding as well .

For the organics, I use would chlorine bleach (>24 hrs soak) first before the muriatic acid.

[twiddybr]

I know this is a very old thread, but I am curing some dry rock and cycling my tank at the same time. No livestock or anything. Any disadvantage to dosing the Seakler in bulk and running a skimmer? Mainly, detrimental effect on the bacterial colonies?