Phosphate Absorption Rates in Aragonite

[teller]

Yes lets keep a remote DSB to handle phosphates..,.hupps.,,.in the mean time someone invented the GFO....let's go living in the past. You do not have to run GFO 24/7. Put a timer for running 4 hours a day or so, more or less.

 

[mcarroll]

Yes lets keep a remote DSB to handle phosphates..,.hupps.,,.in the mean time someone invented the GFO....let's go living in the past. You do not have to run GFO 24/7. Put a timer for running 4 hours a day or so, more or less.

Good idea, but we're just joking around. Really trying to see about phosphate binding to calcium carbonate.

 

[Lasse]

Am I dating myself too much? Does anybody even know what a remote DSB is anymore?

I do

Sincerely Lasse

 

[Randy Holmes-Farley]

Yes lets keep a remote DSB to handle phosphates..,.hupps.,,.in the mean time someone invented the GFO....let's go living in the past. You do not have to run GFO 24/7. Put a timer for running 4 hours a day or so, more or less.

Actually, I'm aginst a timer on a GFO reactor because the water can go stagnant.

 

[Lasse]

I agree with Randy - I once run my GFO reactor on timer and probably had a little for long stop period. suddenly I got a rise in the PO4 level. I was low in nitrate at that time also - the only explanation I can figure out is that my GFO reactor got anaerobic, 0 in nitrate, hence forming of hydrogen sulphide take place and the hydrogen sulphide released PO4 from the FePO4 complex.

Nowadays I run it in small cycles 60 seconds on – 60 seconds off if I want to halve the flow

Sincerely Lasse

 

[jda]

Bertoni, IIRC, had some study that said that bacteria/organics can start to coat GFO in stagnant water and it becomes very much useless. Maybe it was not him, but it was somebody who people respect.

Anyway, forgetting where we have been is a good way to make sure that we do not know where we are going.

Phosphate is here. I will get to testing and stuff a bit later today.

 

[Cory]

I wonder how well powdered caco2 would remove po4 and how much you would need?

 

[Randy Holmes-Farley]

I wonder how well powdered caco2 would remove po4 and how much you would need?

Fairly well. Not as well as GFO. If you leave it in the water, it can come back off.

 

[jda]

Carib Sea Arm soaking for a few days in 32 ounces of water has yielded 183 PPB of Phosphorus in the saltwater in the reactor - Hannah Ultra Low. .561 PPM, if I did the math right. 343 grams of media in 32 ounces of water does not release all the total phosphate in the world, but it is a lot in a 1L concentration... about 7.5ish total PPM if I did the math right from the figures on the last page. In any case, I dumped the water and and started running it on some media for a few days to get it as clean as possible. It will release even more now that the water is free of phosphate around it.

I took a mean diameter on a handful of dry chunks. They are about 19mm. Average weight was 4.5 grams. This is VERY rough - some of them are like footballs, some are squarish, but a pseudo-sphere is as good as I can approximate them to be. This is 283.4 sq mm per hunk. There is 76 chunks at 343/4.5. Total area of 21538.4 sq mm of surface area. Is this helpful at all?

 

[Randy Holmes-Farley]

Total area of 21538.4 sq mm of surface area. Is this helpful at all?

Probably not. The microscopic surface area of rough or porous materials is far, far higher than the apparent size would indicate. That's how a gram of Pukani can have a surface area of 5,000 cm^2.

 

[jda]

It did not seem like it was worth much... number was too low. This stuff is large chunk crushed up dead coral from Florida. If anybody sees any numbers of gulf rock, then maybe the transient property could apply in a horribly inaccurate way.

 

[mcarroll]

Probably not. The microscopic surface area of rough or porous materials is far, far higher than the apparent size would indicate. That's how a gram of Pukani can have a surface area of 5,000 cm^2.

Do you think 5000cm^2 is useful for us, or are you saying that's also too extreme below?

Gases used for these surface area measurements (as BRS did) get into smaller spaces than phosphate in water will.

What method did they use, BTW?

And it seems that I never posted the link to the surface area number I used.....gah! Including both PDF's on this post so you can see what they did.

I wonder why Nauman's technique would be insufficient for our thread? (CT+3D reconstruction – which was apparently novel in 2008. It also yielded a number MUCH higher than other "standard techniques".)

Nauman (2008 – DOI 10.1007/s00338-008-0459-3):
Coral surface area quantification–evaluation of established techniques by comparison with computer tomography

Millero (2001 – https://doi.org/10.1023/A:101134411):
Adsorption and Desorption of Phosphate on Calcite and Aragonite in Seawater

 

[Randy Holmes-Farley]

What method did they use, BTW?

And it seems that I never posted the link to the surface area number I used.....gah! Including both PDF's on this post so you can see what they did.

BRS used a total surface area technique, BET, which absorbs gas onto the available surface area, including area inside pores.

The articles you are referencing are not trying to measure surface area inside of pores. They are measuring the outer edge area only (e.g., where tissue is growing and is exposed to the outside environment).

For example, a baseball sized piece of porous rock will have a huge surface area from internal pores, but only a few tens of cm2 on the outer surface that you can tough with your hands.

 

[mcarroll]

I still wonder then....the "established methods" they used/cited in that paper delivered numbers in the tens as well.

Thier Computer Tomography technique mapped two orders of magnitude more area. xx cm2 vs x,xxx cm2 from the same sample.

Do we really need to compute the added "resolution" that the gas technique appears to bring or is the lion's share of the PO4 load realistically going to be bound to the CT+3D "viewable" area anyway? (Or something closer to that?)

It seems like the BET number might be unrealistic for our purposes since we're talking about rock in natural seawater vs boiling nitrogen.

I hate to bring W into something like this, but their explanation of the use of BET on Activated carbon seemed useful. Activated carbonm apparently rates around 3000 cm2/g. Only 2/3 that claimed for live rock, but still they claimed that it was probably an overestimation and a more realistic technique ought be used for this purpose.

Not claiming that matches our usage case 1:1 but overestimation does seem to be a valid concern with BET.

 

[Randy Holmes-Farley]

I certainly agree that BET is an overestimate. The other methods are not even intending to measure surface area in pores.

 

[jda]

I let the aragonite circulate for a week in 0 PPB water with 550mls of Al Oxide. Then, I put in 1L of fresh seawater and let it soak for about 24 hours, like last time. This time, I got 15 PPB of phosphate. This is not very much phosphate and barely a trace in a larger aquarium (0.000068 ppm in a 180G tank), but it is clear that if the aragonite unbinds quite quickly at 80% in 24 hours, it takes a while for it to get in/out of all of the little pores.

I am going to run it for another week and see how much farther it goes down after another piece of time. It will be interesting to see if this is linear, or what... if so, it should be at 1 or 0 in another week.

For now: 183ppb to start, 15ppb after 1 week in 0ppb water.

 

[Randy Holmes-Farley]

So far so good.

 

[jda]

I got a little sidetracked, but had some time today to mess with stuff.

After more than two weeks of circulation in 0ppb water, the aragonite will still put out 3 ppb in 1L of water when sitting for about a day. There is still some in there - I think that it is pretty evident when combined with the accounts from hobbyists that it is reasonable to take a year or two to be rid of terrestrial phosphate bound in dry rock. I am going to have to live with this trace amount and forge on with the experiment.

Here in the next day, or so, I will add the sodium triphosphate to a concentration of about 1.0 ppm and put the aragonite reactor on it. I will try and test every day to see how much gets bound.

 

[mcarroll]

Interesting data and great work!!!

Keep it coming!

 

[jda]

I overshot my powder. Ended up with a concentration of 3.6 ppm in the 5 gallons. This was 2 teaspoons of the powder. My cheap gram scale broke, so I have no idea how much this was in g... sorry.

I turned the reactor on with the aragonite in it.