How Much Phosphate Can a Phosphate-Free Limestone Absorb?

[JonasRoman]

Hi again, this is a follow up study from me from my previos phosphate kinetic study. I do the opposite here, try to quantify the absorbtion by measure Po4 in the surrounding water. Finished that today aswell.

/Jonas

 

[Dom]

I would think that number varies depending on the size of the stone.

 

[Dom]

Hi again, this is a follow up study from me from my previos phosphate kinetic study. I do the opposite here, try to quantify the absorbtion by measure Po4 in the surrounding water. Finished that today aswell.

/Jonas

Do you have a link to that study?

 

[EnterName]

Hi again, this is a follow up study from me from my previos phosphate kinetic study. I do the opposite here, try to quantify the absorbtion by measure Po4 in the surrounding water. Finished that today aswell.

/Jonas

Do you have a link to that study?

here you go :)

 

[EnterName]

I would think that number varies depending on the size of the stone.

I think it mostly depends on:

• Overall surface area, which is proportional to size and porosity/density
• Bacterial activity (which this study purposefully excluded, so we can ignore that)
• Water flow (which might have a bigger impact when there is bacterial activity, but I'm not sure)

@JonasRoman The HannaChecker HI736 has a precision of of 5µg/L = 0.005mg/L. I assume T+2 (0.125mg/L) and T+3 (0.130mg/L) are simply within this error tolerance, or do you think a dropping pH over time could have re-dissolved some phosphate? Do you still know the T+4 oder T+5 measurements?

 

[JonasRoman]

Do you have a link to that study?

Its my own study. See pdf

 

[JonasRoman]

I think it mostly depends on:

• Overall surface area, which is proportional to size and porosity/density
• Bacterial activity (which this study purposefully excluded, so we can ignore that)
• Water flow (which might have a bigger impact when there is bacterial activity, but I'm not sure)

@JonasRoman The HannaChecker HI736 has a precision of of 5µg/L = 0.005mg/L. I assume T+2 (0.125mg/L) and T+3 (0.130mg/L) are simply within this error tolerance, or do you think a dropping pH over time could have re-dissolved some phosphate? Do you still know the T+4 oder T+5 measurements?

The 2 last value I conside as same as my methods accuracy is 0.005 mg/l PO4.

I agree about the possibility of variations. I think that this stine could absorb more. Tje water was not circulating and approx 22 degree C. With more cirk and warmer its building more hydroxyapatite. Also, the pH may have declined from initial 8.5, so also that could affect. The stone is porous and similar to those we use in tank.
So, with even longer waiting time, warmer, more circulating, and maybe another boost of NaOH to keep pH not below 8.5, would have continued the po4 absorption.
0.07 mg po4 for 300 gram stone is anyway interesting and tell us that stone can absorb a significant amount

 

[Randy Holmes-Farley Verified Community Expert]

I agree that such binding is surface area-dependent.