Results from my home study phosphate binding kinetics

[Fish Fan]

Appreciate

Congrats! Well deserved I'm sure!

 

[JonasRoman]

Hi all friends. First of all thanks for alk feedback and good questions. And for the research award this encourage me to do more investigations. I have always been of that kind I question things and want to understand. Like so many of all members here in this fantastic forum.
Have to mention master Randy here, where I red all his articles back in the days, and have learned so much from him.

Just wanted to mention this and say thanks to a wonderful forum

/Jonas

 

[MnFish1]

But was it a well designed and controlled experiment with nice clean measurements and data and scientifically sound conclusions?

Or is it another example of someone taking a couple of Hanna checker readings, feeding the numbers and the story they wanted to hear into ChatGPT, and letting the AI synthesize a “scientific paper” that is loosely correct but fundamentally wrong on the methods and interpretation?

Because the latter is what I see, none of it stands up to scrutiny.

I can't tell when AI is being used ?

The other half is going back and forth according to the equilibrium for the more loose bridging connections.

This doesn't make sense to me. 1. I don't think you've proved that 0.06 is an equilibrium point (i.e. that once it reaches this point, you can assume all of the loose PO4 is removed. 2. I am not sure you can determine that this loose form of PO4 is doing what you were saying. You would need to use several concentrations of PO4 as well as longer times than 6 hours IMHO - you haven't proved that 0.06 is the equilibrium point for the loose PO4 - thus I don't think you can use it later in the experiment?

 

[JonasRoman]

I can't tell when AI is being used ?

This doesn't make sense to me. 1. I don't think you've proved that 0.06 is an equilibrium point (i.e. that once it reaches this point, you can assume all of the loose PO4 is removed. 2. I am not sure you can determine that this loose form of PO4 is doing what you were saying. You would need to use several concentrations of PO4 as well as longer times than 6 hours IMHO - you haven't proved that 0.06 is the equilibrium point for the loose PO4 - thus I don't think you can use it later in the experiment?

Not all loose bound (bridged CaPo4) is released when I had 0.06 in water. Its an equlibrium, some are left on stone, some are in water (0.06) according to the equlibrium. But then I put the stone in again in clean water and after seeral days po4 was only raised to 0.01 meaning most of the loose bound PO4 WAS actually released, and thats logic, the equlibrium for this loose bound is very much in direction to free PO4 (as the surrounding water was at the beginining with 0 in po4, so concentration gradient was loosing most of it).
Again, look at the data where the water has 0.01 po4 days after days telling us that prior to that most loose bound po4 was released (or at least not much left as water keeps 0.01 in po4).

0.06 was just the equlibrium in my test, that depends on surface area of stone versus water volume etc, so yes, the po4 conc will be something else with other conditions. That is not the point here, the point is to show we have 2 different way of bidning, one quick and loose, and one slow and tight. And approx the time frame for each process, and approx how much the 2 binds in a ratio aspect. The ratio will probably if I have waited severa,l weeks be even more in favour for the hydroxyapatit.

All this is not strange, bone and teeth using the same mechanism, using PO4 to strengthen the CACO3 structure.

/Jonas

 

[Dan_P]

Hi reefers


This experiment is an attempt to investigate the dual mechanisms of phosphate binding to calcium carbonate surfaces within a marine environment. The experiment aims to differentiate between rapid, reversible surface adsorption and long-term, irreversible crystallization. I have posted my study/article as a pdf.
Summary: The results demonstrate that while a significant portion of phosphate binds loosely and can desorb rapidly, approximately 57% of the total bound phosphate undergoes a slower transition into a stable, insoluble phase (likely hydroxyapatite), effectively permanently sequestering the phosphate within the calcareous matrix.

Include as pdf below

/Jonas Roman, Sweden

Sorry for being late to the party. Always enjoy reading about your work.

You may enjoy the attached paper by Millero.

Did you test the hydrochloric acid for phosphate?

The acid wash of the rock might have released phosphate that had diffused into the rock and become loosely bound. This could have caused some of the phosphate to appear to stop coming off the rock.

The rock might contain phosphate before exposing it to a phosphate solution. After the initial acid wash, did you check to see if it was releasing phosphate, i.e., running a blank?

 

[JonasRoman]

Sorry for being late to the party. Always enjoy reading about your work.

You may enjoy the attached paper by Millero.

Did you test the hydrochloric acid for phosphate?

The acid wash of the rock might have released phosphate that had diffused into the rock and become loosely bound. This could have caused some of the phosphate to appear to stop coming off the rock.

The rock might contain phosphate before exposing it to a phosphate solution. After the initial acid wash, did you check to see if it was releasing phosphate, i.e., running a blank?

Hi, welcome:-)
Yes, I agree that not 100% of the PO4 that was released thanks to acidification must be from hydroxyapatit, BUT I think majority is. Because first I cleaned the stone by soak in very acid soultion an hour or so, making it clean from all types of "old" bindnings. Then after the quick release, the stone was washed, and after that ALMOST no more release occured, only 0.01, for several days, which I interpret as mostly of the loose bound PO4 was released, and only po4 left now on stone must be hydroxyapatit, and that one is then released in the last acidification.

Last question, good one, no I didnt, I assumed it was all released. I do not think its so important, as the last acidification was much less acid and less time than the very first "cleaning", meaning that the difference should reflect the new uptake. I mean, that po4 that was not released in the first wash, will probably not be released in the last one, as the first one was much more agrressive (longer and even more acid).

/Jonas

 

[Randy Holmes-Farley Verified Community Expert]

I'm not sure of the implications to a reefkeeper if there are (or are not) some types of phosphate that get bound and become unable to desorb under ordinary reef conditions. In some settings it might simply be that the adsorbed phosphate gets buried under more calcium carbonate that piles on top of it.

That said, do you know of any implications for reefers if your data is correct?

As an aside, I'm not sure if the procedure you used will account for phosphate that is simply part of the calcium carbonate at the start of the study, buried inside it, and that gets released when you do the acid "removal". Taking a bit of the calcium carboante you started with, rinsed or not, and simply dissolving the whole thing in the same amount of acid will detect if that is the source of the detected P (as well as Dans concern about P in the acid), rather than coming from newly formed calcium phosphate.

 

[JonasRoman]

I'm not sure of the implications to a reefkeeper if there are (or are not) some types of phosphate that get bound and become unable to desorb under ordinary reef conditions. In some settings it might simply be that the adsorbed phosphate gets buried under more calcium carbonate that piles on top of it.

That said, do you know of any implications for reefers if your data is correct?

As an aside, I'm not sure if the procedure you used will account for phosphate that is simply part of the calcium carbonate at the start of the study, buried inside it, and that gets released when you do the acid "removal". Taking a bit of the calcium carboante you started with, rinsed or not, and simply dissolving the whole thing in the same amount of acid will detect if that is the source of the detected P (as well as Dans concern about P in the acid), rather than coming from newly formed calcium phosphate.

I do not think hydroxyapatite is formed inside deep in stone but same as for emalj on teeth, on surface or close beneath. That's why I think acid bath will remove it.

Implications for today aquarist may be that it's common nowadays with dead naked stone probably not coated with calcium phosphate, and therefore play a crucial roll in the po4 kinetics the first period of newly set up tank.
I have seen many cases lately of new tanks based on dead rock of different kinds where we see this phenomenon, that po4 is consumed , in hours and after maybe a few months it's suddenly stops and po4 is detectable again.
This kinetic could be a partial explanation.

Jonas

 

[Randy Holmes-Farley Verified Community Expert]

Many types of calcium carbonate have phosphate in them.

 

[JonasRoman]

Many types of calcium carbonate have phosphate in them.

The stone must have some surface and or channels. And yes lime stone has thanks to its porosity. So in a way I think you are right that calciumphospate may formate deeper in BUT still in surfaces where water reach. With that said, I still think my prior acidifacation released relevant hydroxyapatit to show the presence of the new ones released in the second acidification.

Even if there was a mechanism for a stone to incorporate po4 also in the core without channels and pores, that is not making my findings less interesting. It still shows how a " clean" stone (on surface and channels and pores) may absorb po4 in 2 diff ways where one is not released back, and that could explain what we see more today with dead stone in beginning of a newly set up tank. The study also gave us a hint about the time frame for the 2 diff kinds of binding. That is at least my interpretation

Jonas

 

[Randy Holmes-Farley Verified Community Expert]

It gets incorporated during deposition/formation, not after the fact.

https://www.uky.edu/KGS/minerals/im...tone contains unusually,e.g., Pomeroy, 1970).

 

[JonasRoman]

It gets incorporated during deposition/formation, not after the fact.

https://www.uky.edu/KGS/minerals/im...tone contains unusually,e.g., Pomeroy, 1970).

Its the kinetics after that, in the tank, that we talk about. SO the fact that it can incorporate more hydroxyapatite. For sure on surface area, pores etc. In my last acidifation its not likely I release "core" po4 but more likely just those more newly formed po4 bindnngs, thus those on surface and pores, that are involved in this dynamic kinetics. Whats deep inside the core and only can be released if you melt down the stone totally, is not of any interest.
In practial term we see this, stone is cosuming po4 during a quite long period. And not all of this can leak back, Not the hydroxyapatit part.

I plan to do some more tests to also see if I can measure a reduction in the water(need more stone and lower conc of po4), and see if I can show a total and definitive consumption of PO4, and if he acidifaction will release approx same amount that was consumed.

 

[Randy Holmes-Farley Verified Community Expert]

Its the kinetics after that, in the tank, that we talk about. SO the fact that it can incorporate more hydroxyapatite. For sure on surface area, pores etc. In my last acidifation its not likely I release "core" po4 but more likely just those more newly formed po4 bindnngs, thus those on surface and pores, that are involved in this dynamic kinetics. Whats deep inside the core and only can be released if you melt down the stone totally, is not of any interest.
In practial term we see this, stone is cosuming po4 during a quite long period. And not all of this can leak back, Not the hydroxyapatit part.

I plan to do some more tests to also see if I can measure a reduction in the water(need more stone and lower conc of po4), and see if I can show a total and definitive consumption of PO4, and if he acidifaction will release approx same amount that was consumed.

I am pointing out that there may be calcium phosphate in the near surface region at the start of the experiment exactly as there may be calcium phosphate deep inside. You attribute that to a conversion of crystal form, which may be correct, but showing it did not come from the starting material is not difficult, and is necessary to support the conclusion.

 

[Dan_P]

I am pointing out that there may be calcium phosphate in the near surface region at the start of the experiment exactly as there may be calcium phosphate deep inside. You attribute that to a conversion of crystal form, which may be correct, but showing it did not come from the starting material is not difficult, and is necessary to support the conclusion.

Some years ago I reported on the presence of both iron and phosphate in aragonite sand. Natural minerals can be complex mixtures which are affected by how they are formed. This mixture complexity can be a surface phenomenon or exist throughout the solid. This is probably why Millero synthesized his own aragonite when studying phosphate adsorption.

 

[JonasRoman]

I am pointing out that there may be calcium phosphate in the near surface region at the start of the experiment exactly as there may be calcium phosphate deep inside.

But I had the stone in acidity before I started the experiment (below pH 1.0 this first acidification) to remove such preexisting calcium phosphate.

 

[Randy Holmes-Farley Verified Community Expert]

But I had the stone in acidity before I started the experiment (below pH 1.0 this first acidification) to remove such preexisting calcium phosphate.

Correct me if I have misunderstood, but here’s my quickie understanding of what you did.

1. You acid washed and removed some of the surface, not what was underneath.

2. Then you adsorbed and desorbed some phosphate from the surface.

3. Then you dissolved more of the bulk to show there was some nondesorbable phosphate.

But you did not show a control where you skipped step 2 and looked for phosphate that was there all along and got detected in step 3.

 

[JonasRoman]

Correct me if I have misunderstood, but here’s my quickie understanding of what you did.

1. You acid washed and removed some of the surface, not what was underneath.

2. Then you adsorbed and desorbed some phosphate from the surface.

3. Then you dissolved more of the bulk to show there was some nondesorbable phosphate.

But you did not show a control where you skipped step 2 and looked for phosphate that was there all along and got detected in step 3.

No. Point 1 you have misunderstood
I soaked stone for 2 -3 hours in a pH below 1. So not just washed surface. That deep presoaking removed for sure all capo4 on areas (and some deeper( that are reachable for the new formation of capo4.

But I could have added a 1b step to prove that all is gone.

The last acidification was much less aggressive thantjhe first one (step 1) just to be sure its newly formed po4 I deattach.

 

[EnterName]

It might be a stupid idea as it isn't simulating rocks anymore, but if you precipitate CaCO₃ from high purity CaCl₂ and Na₂CO₃/NaHCO₃ you should get "fresh" CaCO₃ without any PO₄ contamination. This would render the acid washes unnecessary and the only contaminants would be "balling salts", NaCl, and CO₂, all of which are absolutely common in reef tanks and can be reduced to a minimum by rinsing the CaCO₃ a few times.

Are bacteria playing a significant role in the binding process? Because in that case I wonder if you would have seen even more phosphate binding when waiting longer for these bacteria to establish.

 

[JonasRoman]

It might be a stupid idea as it isn't simulating rocks anymore, but if you precipitate CaCO₃ from high purity CaCl₂ and Na₂CO₃/NaHCO₃ you should get "fresh" CaCO₃ without any PO₄ contamination. This would render the acid washes unnecessary and the only contaminants would be "balling salts", NaCl, and CO₂, all of which are absolutely common in reef tanks and can be reduced to a minimum by rinsing the CaCO₃ a few times.

Are bacteria playing a significant role in the binding process? Because in that case I wonder if you would have seen even more phosphate binding when waiting longer for these bacteria to establish.

I do honestly not think you'd have to do your own stone.I think it will be fine using already formated stone as I soaked in extremely acid solution for several hours. I'm sure it is absolutely free of phosphate after that treatment, even the hard bounding ones.
Concerning microbiology.I boiled the stone before and I used reference water which is with absolutely no organics, so I don't think there are any bacterial activity at all In my tests

 

[EnterName]

It might be a stupid idea as it isn't simulating rocks anymore, but if you precipitate CaCO₃ from high purity CaCl₂ and Na₂CO₃/NaHCO₃ you should get "fresh" CaCO₃ without any PO₄ contamination. This would render the acid washes unnecessary and the only contaminants would be "balling salts", NaCl, and CO₂, all of which are absolutely common in reef tanks and can be reduced to a minimum by rinsing the CaCO₃ a few times.

Are bacteria playing a significant role in the binding process? Because in that case I wonder if you would have seen even more phosphate binding when waiting longer for these bacteria to establish.

I do honestly not think you'd have to do your own stone.I think it will be fine using already formated stone as I soaked in extremely acid solution for several hours. I'm sure it is absolutely free of phosphate after that treatment, even the hard bounding ones.
Concerning microbiology.I boiled the stone before and I used reference water which is with absolutely no organics, so I don't think there are any bacterial activity at all In my tests

I thought so, but it might have adressed the concerns about residual PO₄ others mentioned.

I don't know much about how these stones form, but if PO₄ accumulates throughout the whole formation of the rock, it might be really hard to get fully rid of it. Dissolving the surface layer of the rock with acid would just expose the underlying layer with just as much phosphate. You would basically need a solution that is capable of releasing bound phosphate without slowly dissolving the rock.

I can still imagine that the residual phosphate in your experiment was negligible and probably didn't exceed the expected error of the used measuring device, but I understand why people are having some concerns about residual PO₄.

I remember reading that you boiled the stone (sounds dangerous btw), and that you did your best to get rid of organics. I was just asking because the measured results might look differently in a reef tank with bacterial activity.