Desorbing phosphate from sand with lanthanum.

[Garf]

Finally got around to a hap hazard test for desorbing sand with lanthanum. The sand has been churning around in my fluidised media reactor for a week on a tank currently measuring 0.6 ppm. From previous measurements in the Aragonite adsorption thread, Dan-P kindly calculated my sand had adsorbed approximately 20mg PO4, from results I had from testing in tank using 1.8 kgs of sand.
My mission here is to see if it’s feasible to re-use this sand cheaply, using lanthanum.

a) Firstly I quickly rinsed the sand in tapwater to remove detritus (there was actually very little).
b) then a very quick rinse in a little RODI.
c) put the sand (1.5 kgs) into RODI (4.5 litres) with a small power head for circulation.
d) added 5 ml of lanthanum according to Randy’s excerpt below.
e) waited 24hrs with occasional stirring.
f) added 3% ish Tropic Marin salt to the test sample so the Hanna would read correctly.

Now, unless I’ve calculated summit wrong with the lanthanum dosage,or done summit really daft, that should bind 23mg phos. My 1.5 kgs of sand is a little lower than the normal 1.8 kgs that I have used previously, so it would churn over better.

Testing the water results in a 0.2 to 0.25ppm concentration. Therefore I’ve concluded that all of the Lanthanum in the dose has been consumed already, so re-dosed.

Ive assumed lanthanum is ok to use in RODI.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, lanthanum will work in RO/DI.

 

[Garf]

Tested again today at 44 hrs, got a 0.07 result. Visually the Hanna had a slight blue tinge, so I tend to believe it. This suggests the second dose of lanthanum has been consumed. This time I filtered the test solution with a coffee filter. So far then that’s 46 mg phosphate removed (I hope) so I’ve added another 2 mls in an attempt not to overshoot, test again tomorrow. I plan on removing my fluidised filter and running it through that soon to speed up the process. Then I’ll just be able to remove it from the regen bucket, rinse, plop it on the tank in seconds.

 

[Garf]

2 hrs after inviting the media reactor to the party, Hanna is reading 0.00.
I think I should remove the solution and replace with straight RODI, to see if leaching has stopped or excess lanthanum is still binding;

 

[Garf]

Alrighty then. The bucket RODI remained at zero. To me this indicates any Phosphate that can be desorbed, indeed has been. Therefore, back on to the tank it goes to load it back up. Hopefully the next few cycles will give an indication in loss of efficiency (by measuring lanthanum consumption), either through permanently bound phosphate or other strange effects that I am unaware of;

The tank;

 

[Randy Holmes-Farley Verified Community Expert]

Alrighty then. The bucket RODI remained at zero. To me this indicates any Phosphate that can be desorbed, indeed has been. Therefore, back on to the tank it goes to load it back up. Hopefully the next few cycles will give an indication in loss of efficiency (by measuring lanthanum consumption), either through permanently bound phosphate or other strange effects that I am unaware of;

The tank;

You might put a little in seawater just to make sure that does not facilitate desorption. I think it might.

 

[Dan_P]

Alrighty then. The bucket RODI remained at zero. To me this indicates any Phosphate that can be desorbed, indeed has been. Therefore, back on to the tank it goes to load it back up. Hopefully the next few cycles will give an indication in loss of efficiency (by measuring lanthanum consumption), either through permanently bound phosphate or other strange effects that I am unaware of;

The tank;

Nice demonstration.

If the is a place to put down bets, I am leaning towards wagering “no loss detected for the next round”.

 

[Garf]

You might put a little in seawater just to make sure that does not facilitate desorption. I think it might.

Probably try that, ta

Nice demonstration.

If the is a place to put down bets, I am leaning towards wagering “no loss detected for the next round”.

got a bloody odd partial result on the next cycle. After adding 5ml lanthanum last time, the test indicated 0.2 to 0.25ppm. This time it’s 0.4ppm. Perhaps I didn’t rinse the sand well enough. I don’t suppose lanthanum that’s unbound to phosphate can bind to calcium carbonate instead, and still bind phosphate?
Oh well, I’ll find out next cycle I suppose, lol.

 

[Dan_P]

Probably try that, ta

got a bloody odd partial result on the next cycle. After adding 5ml lanthanum last time, the test indicated 0.2 to 0.25ppm. This time it’s 0.4ppm. Perhaps I didn’t rinse the sand well enough. I don’t suppose lanthanum that’s unbound to phosphate can bind to calcium carbonate instead, and still bind phosphate?
Oh well, I’ll find out next cycle I suppose, lol.

Not quite a Game of Thrones plot twist but still an interesting development

 

[Randy Holmes-Farley Verified Community Expert]

Probably try that, ta

got a bloody odd partial result on the next cycle. After adding 5ml lanthanum last time, the test indicated 0.2 to 0.25ppm. This time it’s 0.4ppm. Perhaps I didn’t rinse the sand well enough. I don’t suppose lanthanum that’s unbound to phosphate can bind to calcium carbonate instead, and still bind phosphate?
Oh well, I’ll find out next cycle I suppose, lol.

I do expect that lanthanum can bind to calcum carbonate surfaces (with or without bound phosphate exposed), and exposed lanthanum can bind some phosphate on top of it.

 

[Garf]

Ok, got a zero phos this time after 10 mls lanthanum which is 10% to 20%ish lower than last time, however that may well be within my margin of test error.
I’ve actually been running a second test simultaneously. When I take out the fluidised reactor from the tank, I replace it with a bag of sand. I’ve been testing this bag for leaching / regeneration and getting similar results. I must say that taking out a bag, plopping it in a regen bucket with a power head for 24 hrs is a lot less hassle than messing with a media reactor. From previous tests, this bag regen could be done every 3 days efficiently, and the main advantage is the speed of uptake. Currently, 1.5 kgs in a heavily fed 60 gallon, once a week is keeping the status quo. However, this may be only efficient at high phos levels (currently 0.55ppm).
I’ll keep going

 

[Garf]

I’ve slacked on testing the regen bucket and just dosing it with 11 mls lanthanum this week. Changed the bag over twice this week and the phosphate level in the tank has dropped, as if it were new sand. I’ve now employed a 7 inch filter sock with 3 kgs sand in just placed in the sump with extremely mild flow (obviously had to use some new sand to up the quantity). My main problem is that I celebrate any drop of phosphate in the tank with a hefty pinch of algae pellets, the fish get some too

 

[Dan_P]

I’ve slacked on testing the regen bucket and just dosing it with 11 mls lanthanum this week. Changed the bag over twice this week and the phosphate level in the tank has dropped, as if it were new sand. I’ve now employed a 7 inch filter sock with 3 kgs sand in just placed in the sump with extremely mild flow (obviously had to use some new sand to up the quantity). My main problem is that I celebrate any drop of phosphate in the tank with a hefty pinch of algae pellets, the fish get some too

Do you think this method for phosphate removal will catch on? It certainly sounds like a “natural” way to do it (I offer the “natural” suggestion free of charge for your new product )

 

[Garf]

Do you think this method for phosphate removal will catch on? It certainly sounds like a “natural” way to do it (I offer the “natural” suggestion free of charge for your new product )

Probably be as popular as my bubbly CO2 reducer
I’m actually gonna try another version of that, using the aforementioned media reactor.

On a positive note, my LFS has got some fine grain sand that I’m guessing has 10 to 20 times more surface area than what I’m using, therefore phosphate reduction potential, but not too fine as to escape a 100 um filter sock.

 

[Dan_P]

Probably be as popular as my bubbly CO2 reducer
I’m actually gonna try another version of that, using the aforementioned media reactor.

On a positive note, my LFS has got some fine grain sand that I’m guessing has 10 to 20 times more surface area than what I’m using, therefore phosphate reduction potential, but not too fine as to escape a 100 um filter sock.

Will flow through the sand be an issue with the finer sand?

 

[Garf]

Will flow through the sand be an issue with the finer sand?

Maybe, but I really want to regen it Weekly, so it’s got a week to get saturated. My current sand appears to take 3 days, then just sits there, waiting. I would add, I’ve still noticed no obvious difference in coral growth now the tank is at 0.45ppm PO4 (from 1.4 ish). I’ve reached my kalkwasser limit now on this tank, fully saturated with 45mls vinegar per gallon, I’m at maximum evaporation replacement.

 

[areefer01]

Curious question - ease of maintenance as it relates to mess, time, and effort any factor at all?

Looking at it from say a use of GFO compared to LC point of view.

 

[Garf]

Curious question - ease of maintenance as it relates to mess, time, and effort any factor at all?

Looking at it from say a use of GFO compared to LC point of view.

Only ever used GFO once, many years ago, ended up spending 2 years of my life messing with algae scrubbers, lol.

A summary of this is;

Put sand in mesh bag in tank.
Take mesh bag out after 1 week and put it in a bucket with Lanthanum circulating for 24 to 72 hrs.
Quick rinse in RODI.
Put back into tank.

I would add that I’ve only regenerated the sand a few times so far, early days. I normally mess with things for longer.

 

[Dan_P]

Maybe, but I really want to regen it Weekly, so it’s got a week to get saturated. My current sand appears to take 3 days, then just sits there, waiting. I would add, I’ve still noticed no obvious difference in coral growth now the tank is at 0.45ppm PO4 (from 1.4 ish). I’ve reached my kalkwasser limit now on this tank, fully saturated with 45mls vinegar per gallon, I’m at maximum evaporation replacement.

There are some interesting looking goldfish these days. When saltwater aquarium keeping gets too exciting, I am going back to those boyhood shiners

 

[Garf]

Decision time soon. Do I push this low, to see how low it can get (phos at 0.3ppm now)? Create a maintenance schedule to hold it where it is? Push it low and feed the hell out of the tank (will give me a Nitrate challenge)? Remove the bag, to see how fast phos goes back up? Decisions, decisions.