Regenerating GFO

[dkeller_nc]

One comment about regeneration via the "batch" method (i.e., just adding the acid or NaOH to glass container of GFO, giving it a stir and letting it settle). While equilibration in the bulk solution will be nearly instant, it takes some amount of time for the liquid in the pores of the media to equilibrate with the surrounding liquid. How much time depends on the pore size of the media, how big the particles are, and the temperature of the liquid.

This is one explanation of how the 0.01N HCl rinses remained acidic after contact with the regenerated GFO, but the RODI rinse was fairly basic - you may not have left the acidic rinse in contact with the media for a sufficient period of time. In my case, I let the rinse and the GFO stand in the container for at least 10 minutes between rinse changes, which empirically appears to be sufficient for equilibration with Bulk Reef Supply's high-capacity GFO.

That said, I'm not at all sure what the pH of very pure water in contact with GFO would be. It wouldn't surprise me that the pH would turn out to be somewhat basic, though the buffering capacity would be so low that it really wouldn't make any difference for use in a reef tank.

 

[david00061]

What kind of GFO are you regenerating? The only one I have any experience with is BRS High Capacity and we have had no clumping issues.

how much more lye do you use for BRS High Capacity

 

[dkeller_nc]

The 1N NaOH solution typically used is more than enough to regenerate the BRS HC GFO, but you still want to use several successive add/soak/rinse cycles to ensure that you've driven the equilibrium all the way to native GFO (i.e., GFO with little or no phosphate adsorbed to it).

For lye, that's about 40 grams per liter of RODI, or about 6 teaspoons or 2 tablespoons per quart.

 

[david00061]

The 1N NaOH solution typically used is more than enough to regenerate the BRS HC GFO, but you still want to use several successive add/soak/rinse cycles to ensure that you've driven the equilibrium all the way to native GFO (i.e., GFO with little or no phosphate adsorbed to it).

For lye, that's about 40 grams per liter of RODI, or about 6 teaspoons or 2 tablespoons per quart.

Are you saying I should shut pump off and let GFO soak in NaOH solution several times if so how long and how many?
I just ran it through reactor for 84 hours.
i checked phosphate in tank and they are at .32 Hanna test. I check coming out of reactor and they are at .20, is this normal?

 

[dkeller_nc]

I would recommend taking the GFO out of the reactor, putting it into a mason jar, rinsing it thoroughly with tap water to remove built up organics/sludge, then regenerate it by adding 1N NaOH solution at about 2 to 1 GFO volume-to-solution. Mix this thoroughly by stirring, then allow it to stand for at least a few hours if not overnight. Pour the solution off, then repeat twice more. Rinse the heck out of it with RODI to remove the excess NaOH solution (this might take as many as 10 rinses).

Some, including me, add an additional dilute hydrochloric acid (0.05 N or so) soak before using the NaOH solution to remove any precipitated calcium carbonate.

Some store the regenerated GFO wet, though I prefer to dry mine in a glass baking dish in the oven.

A tip: wear rubber dishwashing gloves when manipulating the NaOH. Even a brief splash will remove the fats/oils from your skin, and cause hardening/dermatitis. Nothing like a bad acid burn, but unpleasant nonetheless.

 

[david00061]

What is dilute hydrochloric acid (0.05 N?

 

[trueperc]

Hello, I thanks this thread for saving me a tone of money. I have been regenerating gfo for the past three years. Usually brs stuff. For the past year hrs HC which I find the best so far. However I was wondering has any one regen rowaphos with out any issues as I just picked up a great deal on a large 5kg bucket.

 

[Randy Holmes-Farley]

What is dilute hydrochloric acid (0.05 N?

Full strength muriatic acid (hydrochloric acid) from the hardware store is about 12 N. So you need to dilute it something like 1 part muriatic acid into 250 parts fresh or RO/DI water.

 

[david00061]

What is dilute hydrochloric acid (0.05 N?

Full strength muriatic acid (hydrochloric acid) from the hardware store is about 12 N. So you need to dilute it something like 1 part muriatic acid into 250 parts fresh or RO/DI water.

thanks

 

[david00061]

So, how much lye should i add to each soak? i want to regenerate 7 cups of GFO each time

 

[dkeller_nc]

So, how much lye should i add to each soak? i want to regenerate 7 cups of GFO each time

A bit of a clarification - I stated above that I use a 2:1 ratio of NaOH solution to the volume of GFO to be regenerated. My actual usage is somewhat less than this - for 1 cup of GFO, I use enough NaOH solution to give me a total volume of 2 cups.

While I've never done any experimentation to prove it, I doubt the ratio is all that critical.

 

[david00061]

should gfo be rinse thoroughly with r/o between soaks

 

[bheron]

definitely. you can feel the sliminess when you first rinse it.

 

[FullBoreReefer]

Would something like this work?...

http://www.bulkapothecary.com/raw-i...droxide-lye/?gclid=COCRw4S6kMACFbTm7AodACEAXA

I have never done this the "regenerating" stuff but have been saving my gfo for a couple months in hopes to try it. Is there somewhere you would recommend getting it? Or cheaper(not that its expensive, but)?


Thanks!

 

[dja1980]

That might be a good find... I e-mailed Bulk Reef Supply a few months ago to see if they might be interested in offering this, but they said they had safety concerns. I don't know what their margin is on the HC GFO, but I would think they they could make the margin on Sodium Hydroxide even higher, and reefers would gladly purchase it due to savings compared to HC GFO. It seems like it would be a win-win for everyone, and they could even make one of the how-to videos on the subject. Oh well... maybe one day they'll change their mind. It would be nice to purchase this along with all my other bulk reef products from BRS.

 

[Randy Holmes-Farley]

Would something like this work?...

http://www.bulkapothecary.com/raw-i...droxide-lye/?gclid=COCRw4S6kMACFbTm7AodACEAXA

I have never done this the "regenerating" stuff but have been saving my gfo for a couple months in hopes to try it. Is there somewhere you would recommend getting it? Or cheaper(not that its expensive, but)?


Thanks!

That is a fine grade of sodium hydroxide for any reef use.

 

[FullBoreReefer]

My lye showed up today. Mixed up a liter to 1m, then added 4 cups of gfo and 8 cups solution into a container. Let the soaking begin...

 

[david00061]

I rinsed used GFO (7 cups) with tap water till pretty clean.
Nexted I soak with 15 cups of ro/di and a cap of Full strength muriatic acid (hydrochloric acid) for a few hours rinsed with ro/di.
I used a half of cup of lye and 15 cups of ro/di 7 cups of GFO let soak for 24 hours, stirring every once in a while. Rinse with ro/di. repeated 2 more times. Does this sound right?

After running GFO thru reactor for 24 hours I test tank water it is 0.15. I test water coming out of reactor it is 0.09. Does this sound like a good reduction of Phosphate? Or should it be reduced more?

 

[dkeller_nc]

Your regeneration procedure sounds about right, and your 1/2 cup of solid lye to 15 cups of RODI should make about 3.5 liters of approximately 1M NaOH. However, one thing you didn't mention is rinsing after the regeneration - it's essential that you get as much NaOH out of the GFO as reasonably possible. That might take as much as 10 rinses with RODI, as the GFO is porous and it takes a while for the NaOH solution in the pores to diffuse into the bulk solution so that it's removed by the rinses.

Adding a little bit of NaOH to your tank water by virtue of some being left in the GFO isn't a big deal, it will just boost your alkalinity a bit. But if a lot's left in the GFO, that might boost your alkalinity way more than you want.

From the standpoint of the in/out concentration measurements from your GFO reactor, your results sound OK. There's a lot of imprecision in phosphate tests, and whether all, most, or just a little of the incoming phosphate is absorbed depends on a lot of complex factors like particle size of the media, bed height of the media, and flowrate.

A better assessment is simply to measure your tank water's phosphate concentration over a few days. You should see a gradual downward trend followed by a leveling off. When the phosphate concentration begins to rise over a few day's measurements, it's time to change out the GFO.

 

[david00061]

I'm using BRS HC GFO I did rinse it 10 times. I'm using a 4" reactor. How much flow do you recommend? I have it so it just moves a little throughout the reactor