The Science Of Sand Washing

[Dan_P]

I did look at it.
The polyquat algaecides didn't show any reduction in aragonite cloudiness that I could measure in a cuvette.
(I also cultured up a cloudy bacterial bloom and then killed it with heat and couldn't measure any removal of cloudiness with the algaecides.)
That doesn't mean it wouldn't be detectable clearer through 2 ft of tank water, but in ~1cm nothing I could quantify.
I also didn't think to compare to the Seachem Clarity etc polymers like polyDADMAC specifically for clarifying.

I just figured a polyquat is a polyquat is an algecide.

I didn’t realize polyDADMAC was Clarity. I have a small bottle of the brown liquid. It didn’t do anything to calcium carbonate cloudiness that was obvious, though in retrospect, I did not give it a disciplined test. Maybe I will give it a try and also see if it kills algae.

 

[Randy Holmes-Farley]

I just figured a polyquat is a polyquat is an algecide.

I didn’t realize polyDADMAC was Clarity. I have a small bottle of the brown liquid. It didn’t do anything to calcium carbonate cloudiness that was obvious, though in retrospect, I did not

I just figured a polyquat is a polyquat is an algecide.

I didn’t realize polyDADMAC was Clarity. I have a small bottle of the brown liquid. It didn’t do anything to calcium carbonate cloudiness that was obvious, though in retrospect, I did not give it a disciplined test. Maybe I will give it a try and also see if it kills algae.

Antimicrobial polymers are not usually very high in molecular weight, while flocculant are large to span between particles.

Polymer Flocculants

'Polymer Flocculants' published in 'Encyclopedia of Polymeric Nanomaterials'

link.springer.com

“Their molecular weight ranges from several million to less than 20 million. Cationic polymer flocculants are fully quaternized with methyl chloride and therefore positively charged over a wide pH range.

 

[taricha]

I didn’t realize polyDADMAC was Clarity. I have a small bottle of the brown liquid.

I don't know that it is. I just meant that Clarity is a polymer meant to act like polyDADMAC does, so just guessing they are similar.

 

[Tenecor Aquariums]

I just figured a polyquat is a polyquat is an algecide.

I didn’t realize polyDADMAC was Clarity. I have a small bottle of the brown liquid. It didn’t do anything to calcium carbonate cloudiness that was obvious, though in retrospect, I did not give it a disciplined test. Maybe I will give it a try and also see if it kills algae.

Polydadmac is not an algaecide per se. Polyquat is a polymeric quaternary ammonium compound (PCQ) used as a biocidal and disinfectant agent. It is used to control the growth of microorganisms on surfaces, in liquids, and in air. Polydadmac is another quaternary ammonium compound (QAC) used as a biocidal and disinfectant agent, but it is made with several different quaternary ammonium cations. The primary difference between polyquat and polydadmac is that polyquat is cationic, while polydadmac is non-cationic. Polydadmac also tends to have a longer residual activity than polyquat, making it more effective in certain applications.

 

[Tenecor Aquariums]

To the person who PM'd me. Yes, polydadmac is inert and safe. It is a synthetic polymer synthesized from polyethylene oxide and polymethylene oxide and has properties similar to cellulose, making it non-toxic and free from VOCs (Volatile Organic Compounds). Polydadmac is highly effective in providing a wide range of cleaning, clarification, odor control and conditioning benefits to many industrial processes and products. And it clears up aquariums!

 

[Randy Holmes-Farley]

Much of the previous two posts is just not true at all.

Of course polydiallyldimethyl. ammonium chloride is cationic. Every single monomer is positively charged. The ammonium nitrogen is quaternary and cationic.

I have to say that I’m pretty certain I’m the only member of reef2 reef who has synthesized antimicrobial polymers and polydiallyldimethylammonium chloride. None of these materials can be made from polyethylene oxide or polymethylene oxide, and it has almost nothing in common with cellulose.

 

[Tenecor Aquariums]

Much of the previous two posts is just not true at all.

Of course polydiallyldimethyl. ammonium chloride is cationic. Every single monomer is positively charged. The ammonium nitrogen is quaternary and cationic.

I have to say that I’m pretty certain I’m the only member of reef2 reef who has synthesized antimicrobial polymers and polydiallyldimethylammonium chloride. None of these materials can be made from polyethylene oxide or polymethylene oxide, and it has almost nothing in common with cellulose.

I think you sir are correct. I will be having a conversation with some people tomorrow morning.

 

[taricha]

Back to the solubility question, for a moment...

This data makes clear that wash water turbidity rapidly increases with the time that sand is exposed to tap water. Interestingly, stirring aragonite sand for one hour in tap water resulted in wash water resembling a thin, translucent white paint.

Aragonite is typically formed by living organisms and is less stable than calcite,..The consequence is that when aragonite dissolves in water (calcium carbonate is slightly soluble in freshwater), the concentration of calcium carbonate exceeds the solubility limit of calcite and crystals form. This dissolution-crystallization process can continue as long as there is aragonite present because crystallization continually removes calcium carbonate from solution, allowing more aragonite to dissolve. Stirring aragonite sand for an hour created a large amount of microscopic crystals that formed an emulsion-like mixture resembling thin paint.

So Dan, your water as a conveyor belt slowly dissolving aragonite CaCO3 to its higher solubility and precipitating calcite CaCO3 due to its lower solubility, is simply a consequence of the solubility fundamentals...

Dissolution of a solid stops when the multiplication product of the concentrations of the components it turns into on dissolution hit a certain threshold, called the Ksp, the solubility product constant.

In this case, it is the concentration of calcium times the concentration of carbonate.

So simply vigorous stirring provides agitation that speeds up calcite to precipitate and keeps exposing fresh aragonite to the water that's losing calcite. No other weird local mechanism like higher or lower small scale temperatures needed to explain the conveyor belt.

Makes you wonder if the process is normally halted when things settle down enough that calcite precipitation covers some of the aragonite.

(off topic, but this also gives me a good candidate mechanism that could produce the large amounts of super-fine CaCO3 dust in my old sandbed that started entirely as large aragonite grains)

 

[Dan_P]

So simply vigorous stirring provides agitation that speeds up calcite to precipitate and keeps exposing fresh aragonite to the water that's losing calcite. No other weird local mechanism like higher or lower small scale temperatures needed to explain the conveyor belt.

The conveyor belt is powered by the precipitation of calcite. A lack of precipitation would stop the aragonite dissolution no matter how powerful the mixing. I wonder if we used a very high concentration of Mg++, we could stop calcite formation and the conveyor belt.

Makes you wonder if the process is normally halted when things settle down enough that calcite precipitation covers some of the aragonite.

The notion of the aragonite sand grains becoming covered with calcite crystals might need further modeling (debate). On the extreme end of things, calcite precipitates on the aragonite grain surface or the Ca++ diffuses away and then precipitates as a separate particle. The surface crystallization could lead to the cementing of sand grains while individual particle formation leads to ”dust” formation. For me the aragonite system is dustier than the silicate version.

(off topic, but this also gives me a good candidate mechanism that could produce the large amounts of super-fine CaCO3 dust in my old sandbed that started entirely as large aragonite grains)

We are totally in alignment here.

Also, there is a notion that sand beds dissolve over time. I will take that idea further and propose that pure calcite beds might be more resilient, only succumbing to the low pH of the beds but not the background dissolution that aragonite suffers from.

 

[taricha]

The conveyor belt is powered by the precipitation of calcite. A lack of precipitation would stop the aragonite dissolution no matter how powerful the mixing. I wonder if we used a very high concentration of Mg++, we could stop calcite formation and the conveyor belt.

I was thinking that in a solution that is super-saturated, precipitation can be driven my mixing/agitation and presence of other crystals.
So maybe just mixing the water vigorously speeds calcite crystal formation falling out of the super-saturated solution.

Also, in the past you've used chelating agents to prevent saltwater precipitation during chemical tests. Could one of these chelating compounds stop precipitation in a useful way or would it just increase how much CaCO3 the water can hold and thus not slow down aragonite dissolution?

 

[brandon429]

I guarantee if Dan and Taricha make a team-based podcast or youtube page on reefing chemistry it will be popular and might even allow for early sustained retirement / loads of cash. I will subscribe for sure. hurry up and get it on tik tok before it's banned and no longer a revenue stream, you might could pull a hundred grand off chemistry companies that pay you there for legit endorsements of chemistry items or procedure before the app is yanked all around.

 

[Randy Holmes-Farley]

Also, in the past you've used chelating agents to prevent saltwater precipitation during chemical tests. Could one of these chelating compounds stop precipitation in a useful way or would it just increase how much CaCO3 the water can hold and thus not slow down aragonite dissolution?

You'd need a different type of chemical.

A standard chelator will speed dissolution by effectively lowering the free calcium concentration.

I did experiments with polyacrylic acid years ago and it coats bare calcium carbonate surfaces and prevents precipitation. I could push supersaturation very high (adding B-ionic two part alk portion to tank water) before it crashed out faster than the polymer could coat new surfaces formed. Similar experiment without the polymer precipitated much earlier.

 

[taricha]

I guarantee if Dan and Taricha make a team-based podcast or youtube page on reefing chemistry it will be popular

hehe. Thanks.

I'll update ya if we ever get around to posting something
https://www.youtube.com/@mythsandmeasurements/about

 

[brandon429]

subbed!

 

[PotatoPig]

Sorry if I missed it, but is the Aragonite dissolving or grinding?

From the description of getting an almost paint like consistency from an hour mix it sounds like the relatively soft material is just getting knocked around too much when mixing and grinding itself into an ultra fine suspension?

 

[Tamberav]

This may be off topic kind of...

but what I do is buy fairly clean sand like reef flakes then wash a small amount under tap at a time with a metal strainer. It is fairly quick process for a shallow sand bed in small to moderate size tanks and doesn't waste water.

I found putting it all in a bucket and trying to rinse it took longer and wasted my time and water.

I have also ripped clean sand by putting it in the same metal strainer (they are stainless I believe) and simply shake it like I am panning for gold in old tank water bucket. This was to preserve the large number of spaghetti worms I had. Worked to well to clear debris while keeping larger organisms alive. I did that for a 20g nano.

 

[Dan_P]

I was thinking that in a solution that is super-saturated, precipitation can be driven my mixing/agitation and presence of other crystals.
So maybe just mixing the water vigorously speeds calcite crystal formation falling out of the super-saturated solution.

Also, in the past you've used chelating agents to prevent saltwater precipitation during chemical tests. Could one of these chelating compounds stop precipitation in a useful way or would it just increase how much CaCO3 the water can hold and thus not slow down aragonite dissolution?

I thought about sodium citrate but stopped when I remembered how much it took to solubilize Mg++. I didn’t have that much left in the bottle to try. Could be a future experiment!

 

[jda]

For practical purposes, put 3 to 4 inches of sand in the bottom of a 5 gallon bucket. Stick a hose in the bottom, constantly move it around and rinse until the overflowing water is clear. You can do a pretty darn good job - not perfect, but really good. For a 20 lb sack of sand, I do 1/3 to 1/4 of the bag at a time.

With larger particle sizes, you can get the stuff almost perfectly clean.

This is not a good idea if your tap water is horrible and you are worried about what nasty compounds will bind to the aragonite.

I read this method from ReefmanRon a long time ago and it is the best that I have ever seen.

 

[Daniel@R2R]

For practical purposes, put 3 to 4 inches of sand in the bottom of a 5 gallon bucket. Stick a hose in the bottom, constantly move it around and rinse until the overflowing water is clear. You can do a pretty darn good job - not perfect, but really good. For a 20 lb sack of sand, I do 1/3 to 1/4 of the bag at a time.

With larger particle sizes, you can get the stuff almost perfectly clean.

This is not a good idea if your tap water is horrible and you are worried about what nasty compounds will bind to the aragonite.

I read this method from ReefmanRon a long time ago and it is the best that I have ever seen.

Thanks for this! I'll do this in prep for the new build.

 

[BirdFish5000]

I misread the title as "the science of sandwich"