Safe to mix Sodium Hydroxide and lanthanum chloride in same solution?

brmreefer · Jan 31, 2021

I want to double the use of a dosing container since I have limited space. The dosing container is primarily used to dose sodium hydroxide/sodium sulfate in the evenings (part of the DIY 2-part mixture provide by @Randy Holmes-Farley on R2R). I want to use the same container to dose lanthanum chloride/RODI solution in the morning. I know the titled question is asking about mixing solutions, but in fact I am more concerned with each solution's left over residual content coming in contact with the next day's main dosing solution.

Should I re-consider this method due to some adverse affect from the solutions coming in contact with each other?

Randy Holmes-Farley · Feb 1, 2021

No, lanthanum hydroxide will precipitate.

Lanthanum hydroxide - Wikipedia

en.wikipedia.org

"Lanthanum hydroxide can be obtained by adding an alkali such as ammonia to aqueous solutions of lanthanum salts such as lanthanum nitrate. This produces a gel-like precipitate that can then be dried in air"

brmreefer · Feb 1, 2021

Thank you, sir. I had a feeling they couldn't, so I am glad I asked.

Randy Holmes-Farley · Feb 2, 2021

You're welcome.

Happy Reefing.

spicymikey · Apr 10, 2023

Randy Holmes-Farley said:
No, lanthanum hydroxide will precipitate.

Lanthanum hydroxide - Wikipedia

en.wikipedia.org

"Lanthanum hydroxide can be obtained by adding an alkali such as ammonia to aqueous solutions of lanthanum salts such as lanthanum nitrate. This produces a gel-like precipitate that can then be dried in air"

Hi Randy,

I know this is an old thread but this is my exact question as well. I already searched a bit online about the reaction of these two being mixed in H2O. I also did a small sample mix. Sure, there is a solid white precipitate produced. I am assuming it is the La(OH)3 and not the NaCl from the reaction:
==> LaCl3 + NaOH = La(OH)3 + NaCl

But is that really a problem? Other articles talk about how Lanthanum Hydroxide is also a good binder for PO4, maybe even better. So, I'm wondering what would happen if La(OH)3 was released into seawater with PO4. Would it bind and create LaPO4 with OH releasing into the water to assist with total alkalinity? If so, then this could be a good result and save on separate dosing containers, assuming the correct ratios were calculated for a solution to be used.

Randy Holmes-Farley · Apr 10, 2023

spicymikey said:
Hi Randy,

I know this is an old thread but this is my exact question as well. I already searched a bit online about the reaction of these two being mixed in H2O. I also did a small sample mix. Sure, there is a solid white precipitate produced. I am assuming it is the La(OH)3 and not the NaCl from the reaction:
==> LaCl3 + NaOH = La(OH)3 + NaCl

But is that really a problem? Other articles talk about how Lanthanum Hydroxide is also a good binder for PO4, maybe even better. So, I'm wondering what would happen if La(OH)3 was released into seawater with PO4. Would it bind and create LaPO4 with OH releasing into the water to assist with total alkalinity? If so, then this could be a good result and save on separate dosing containers, assuming the correct ratios were calculated for a solution to be used.

That's a complex question, but I think the precipitation greatly complicates alk dosing and control.

Since it lanthanum oxide/hydroxide may not dissolve when dosed, you may be mostly or completely adding insoluble particulates. Thos particles may bind phosphate just likely alumina (phosguard,e tc.) or GFO, , but isn't an alk supplement.

spicymikey · Apr 11, 2023

Randy Holmes-Farley said:
That's a complex question, but I think the precipitation greatly complicates alk dosing and control.

Since it lanthanum oxide/hydroxide may not dissolve when dosed, you may be mostly or completely adding insoluble particulates. Thos particles may bind phosphate just likely alumina (phosguard,e tc.) or GFO, , but isn't an alk supplement.

Good point. I was focusing more on the La(OH)3 bound to the PO4 particles being a "detritus" that would need to be vacuumed out, similar to the LaPO4 particles left after the LaCL3 binds with the phosphates. That, I suppose, is manageable since I siphon my gravel and sump alternating weeks. But if its keeping the OH molecules from binding with the phosphates then its not effective for the second key goal.

Do you know what happens exactly when La(OH3) binds with PO4? I was looking for chemical calculators online but they all seemed to be just for balancing. We want to know what the right side of the equation would be.

Randy Holmes-Farley · Apr 11, 2023

spicymikey said:
Good point. I was focusing more on the La(OH)3 bound to the PO4 particles being a "detritus" that would need to be vacuumed out, similar to the LaPO4 particles left after the LaCL3 binds with the phosphates. That, I suppose, is manageable since I siphon my gravel and sump alternating weeks. But if its keeping the OH molecules from binding with the phosphates then its not effective for the second key goal.

Do you know what happens exactly when La(OH3) binds with PO4? I was looking for chemical calculators online but they all seemed to be just for balancing. We want to know what the right side of the equation would be.

If it dissolves first, and then precipitates, it forms the same thing lanthanum chloride does: lanthanum phosphate and lanthanum carbonate and possible lanthanum oxide.

If you have particles, then it binds phosphate just like aluminum oxide or GFO, with the negatively charged oxygen atoms of phosphate attaching to positively charged aluminum or iron ions exposed at the surface.

bozo · Apr 11, 2023

If you use LaCl, you should be using very fine filter socks. Like 10 micro and lower. Your socks will clog up fast depending on the amount of phosphate it binds.

I’ve had my tangs react adversely as a result of the precipitate staying in the water column.

I’d dose super slowly and not mix it with anything else

spicymikey · Apr 12, 2023

Just an up

CON CAC said:
If you use LaCl, you should be using very fine filter socks. Like 10 micro and lower. Your socks will clog up fast depending on the amount of phosphate it binds.

I’ve had my tangs react adversely as a result of the precipitate staying in the water column.

I’d dose super slowly and not mix it with anything else

Good advice. Many people seem to get burned by that fact. Because of that I slow drip it into the first receiving chamber before a dense filter mat. No problems really doing it that way. I've heard people drip it into a skimmer, but from my experience that is not effective, probably because LaPO4 not charged . Its just a insoluble solid heavier than water from what I understand.

spicymikey · Apr 12, 2023

Randy Holmes-Farley said:
If it dissolves first, and then precipitates, it forms the same thing lanthanum chloride does: lanthanum phosphate and lanthanum carbonate and possible lanthanum oxide.

If you have particles, then it binds phosphate just like aluminum oxide or GFO, with the negatively charged oxygen atoms of phosphate attaching to positively charged aluminum or iron ions exposed at the surface.

Thanks Randy. Here is some results from observations during simple test yesterday after your post.

LaCl3 + NaOH + H2O results in some lighter than water gel substance. Seems to be Lanthanum Hydrochloride according to online sources - Na(OH)3. .

When I add tank water to this mix the gel mostly breaks down into tiny solid particles which look like what results when LaCL3 is mixed directly with tank water. There is a small amount of gel substance left but most is gone.

I'm totally guessing but I suspect the phosphate in the water was bound up from the La(OH)3 and accomplished the same thing as dosing LaCL3 alone. HOWEVER, since this initial mixing of LaCl3 + NaOH creates this gel, it does not lend itself to auto dosing. Since the goal is to dose it with something else, this clearly won't work. I'll look for other ways to save on dosing pumps.

Randy Holmes-Farley · Apr 12, 2023

spicymikey said:
LaCl3 + NaOH + H2O results in some lighter than water gel substance. Seems to be Lanthanum Hydrochloride according to online sources - Na(OH)3. .

I presume you meant to write lanthanum hydroxide.

spicymikey · Apr 13, 2023

Randy Holmes-Farley said:
I presume you meant to write lanthanum hydroxide.

Yes. Thanks for pointing that out

spicymikey · Apr 25, 2023

FYI Randy, and anyone else interested...

In the end I used my existing Mag Chloride dosing container to play double duty for the Lanthanum Chloride. They mix together with no reaction. I put them into the proper proportions based on prior usage and I am now trying out this mix to auto dose Mag and Lanthanum to the tank. Been doing it for a week and it seems to be working. PO4 is stable under 0.1ppm and Mag is staying around 1350ppm. I suspect the ratio will need to change over time but I only use a 2.5 liter container so adjustments are easy enough when the time comes. Thanks for all the help!