Regenerating GFO

[Randy Holmes-Farley]

It is sold wet by many companies. Not sure if there is a reason for that, but I can at least imagine that if you dry it out, small pores may close as the water leaves them, and may just not reopen on rehydration. In any case, I can't see any advantage to drying it.

 

[tmz]

Would drying it out before storing it be advisable?
I plan to put mine into a sealed container and keep it until I need to rotate gfo in use . It'll be stored for at least a month. If I store it moist should I worry about bacteria, etc?

 

[Randy Holmes-Farley]

No, it won't go bad.

 

[alanmorehead]

I read through this thread last night and was looking at doing some tests in the next few days. I have a Hanna photometer and some BRS pelletized GFO (new and exhausted). It looks like there is somewhat of a general consensus on the process.
What do you think of this test routine?

Step 1) Vinegar Pre-Rinse
Purpose: To remove precipitated calcium carbonate on the surface of the GFO
a) Mix 0.5 gallons of distilled vinegar in 1.5 gallons of RO/DI water in 5g bucket
b) Test PO4
c) Add 5 cups of exhausted BRS pelletized GFO
d) Test PO4 after 1 hour
e) Test PO4 after 2 hours
f) Empty 5g bucket and dump GFO in a cup

Step 2) Sodium Hydroxide Soaking
Purpose: To release bound phosphates from GFO media
a) Mix 640 grams NaOH in 4 gallons of RO/DI water (~1M NaOH solution)
b) Test PO4
c) Add 5 cups of pre-rinsed BRS pelletized GFO
d) Test PO4 after 1 hour
e) Test PO4 after 2 hours
f) Test PO4 after 6 hours
g) Test PO4 after 12 hours
h) Test PO4 after 24 hours

Step 3) Test Effectiveness of Regenerated GFO
Purpose: To see if it works, duh
a) Rinse GFO in RO/DI water
b) Test PO4
c) Add 5 cups of regenerated BRS pelletized GFO to reef tank
d) Test PO4 after 12 hours
e) Test PO4 after 24 hours

Any benefit to boiling the water?
Should I measure pH?
Use more or less vinegar?
Use more or less NaOH?
Wait longer for soaking?

- Alan

 

[tmz]

Thanks Randy, Drying it out is a nuisance. Not doing it saves some work.

How long should the sodium hydroxide soak last. Is 7 days necessary/less?

 

[redfishsc]

Alan, I can't answer any of your questions, but thank you for systematizing this. I am sure that your efforts and those of folks contributing to this thread will quickly produce a fairly simple step-by-step for regenerating GFO.


This thread alone has me considering using GFO. I avoided it it in the past because of the expense involved (which admittedly isn't THAT much esp. since my phosphate is already in the "low" range, ~0.05ppm).

 

[ScooterTDI]

Any benefit to boiling the water?
Should I measure pH?
Use more or less vinegar?
Use more or less NaOH?
Wait longer for soaking?

- Alan

What water are you thinking about boiling? The soak water?

I wouldn't bother with measuring the pH of anything. It won't tell you anything meaningful.

Vinegar and NaOH soaks look fine to me. I think you could get away with less NaOH if you wished. I have a 0.5M solution would work fine. I've been meaning to test this, but I have been a little busy lately.

Scott

 

[ScooterTDI]

Wait longer for soaking?

- Alan

I would base the soak time on the PO4 measurements you get. If there is still a significant change between the last two PO4 measurements, then I'd wait for an additional soak period. When the last two measurements are not significantly different (or there is only a minor change), then I'd consider it finished. I'd then pour off the liquid, rinse the GFO thoroughly with DI, and add fresh NaOH solution and soak for an additional period to see if the original soak volume was sufficient to remove all of the PO4 from the GFO.

Scott

 

[trueperc]

I am just wondering if any body has tried or see any problems in using this regen process on the higher end gfo from bulkreef the High Capacity Gfo or using it on the Rowaphos stuff?

 

[ScooterTDI]

I forgot to mention that the samples for testing may require pH adjusting, especially the NaOH soak solutions. I know that the API test kit required the pH of the NaOH soak solutions to be adjusted down with acid until very little of bottle #1 (acid) was required to drive the pH low. You will need to use a PO4-free acid for this, so test a diluted acid sample for PO4 before doing this.

Also, you may want to test blank samples (i.e. samples that have all of the same reagents, but have not been exposed to the GFO). This will ensure that your testing will actually reflect the PO4 from the GFO and not some PO4 from your reagents. This may be especially important for the vinegar.

Scott

 

[Randy Holmes-Farley]

How long should the sodium hydroxide soak last. Is 7 days necessary/less?


I suspect it is overkill, if you have adequate mixing, but do not know for sure,. When I've equilibrated phosphate containing solutions with GFO for testing at reef pH, it was always stabilized (fully equilibrated) after 48 h

 

[alanmorehead]

What water are you thinking about boiling? The soak water?

The vinegar bath. I didn't know if this would help or not since the vinegar pre-rinse will be relatively short.

I wouldn't bother with measuring the pH of anything. It won't tell you anything meaningful.

ok

Vinegar and NaOH soaks look fine to me. I think you could get away with less NaOH if you wished. I have a 0.5M solution would work fine. I've been meaning to test this, but I have been a little busy lately.

I will go with a ~0.5 M NaOH solution then. I see that NaOH solutions greater than that are supposed be be labeled corrosive.

I would base the soak time on the PO4 measurements you get. If there is still a significant change between the last two PO4 measurements, then I'd wait for an additional soak period. When the last two measurements are not significantly different (or there is only a minor change), then I'd consider it finished.

That was kind of my idea. I want to do a tests after 1 and 2 hours, then less frequent tests after that.

I'd then pour off the liquid, rinse the GFO thoroughly with DI, and add fresh NaOH solution and soak for an additional period to see if the original soak volume was sufficient to remove all of the PO4 from the GFO.

Ok, good idea.

I am just wondering if any body has tried or see any problems in using this regen process on the higher end gfo from bulkreef the High Capacity Gfo or using it on the Rowaphos stuff?

I don't think there should be any issue with the HC GFO. The Rowaphos may not work well if it's similar to Phosban (comment earlier in this thread about this)

I forgot to mention that the samples for testing may require pH adjusting, especially the NaOH soak solutions. I know that the API test kit required the pH of the NaOH soak solutions to be adjusted down with acid until very little of bottle #1 (acid) was required to drive the pH low. You will need to use a PO4-free acid for this, so test a diluted acid sample for PO4 before doing this.

Also, you may want to test blank samples (i.e. samples that have all of the same reagents, but have not been exposed to the GFO). This will ensure that your testing will actually reflect the PO4 from the GFO and not some PO4 from your reagents. This may be especially important for the vinegar.

Ok, that's what my "b" steps are for

 

[Randy Holmes-Farley]

I will go with a ~0.5 M NaOH solution then. I see that NaOH solutions greater than that are supposed be be labeled corrosive.


I'm not sure why that particularly concerns you, but even 0.1 M NaOH is also definitely corossive per regulatory standards (which I believe in the US is pH 12.5 or higher for a base). 0.1 N NaOH will have a pH about 13.

 

[ScooterTDI]

Ok, that's what my "b" steps are for

Sorry, I missed that.

Scott

 

[tatuvaaj]

I'm not sure why that particularly concerns you, but even 0.1 M NaOH is also definitely corossive per regulatory standards (which I believe in the US is pH 12.5 or higher for a base). 0.1 N NaOH will have a pH about 13.

Here in EU "R-phrases" (http://en.wikipedia.org/wiki/List_of_R-phrases) go as follows:

0.5 M : R36/38 - Irritating
1.0 M : R34 - Corrosive
1.66+ M : R35 - Strongly corrosive

 

[paraletho]

We regenerated about 4 cups of BRS High Cap GFO and have it installed in the reactors on our 58 and 125 gallon mixed reefs. We are having no issues other than a brief ph spike of about .5. (8.0 to 8.5) for about 2 or 3 minutes. Probably due to insufficient rinsing. It's doing the job. We see no rise in phosphate as measured by Salifert in the week that it has been in. +1 to tatuvaaj for starting this thread.

 

[redfishsc]

Fantastic, thanks for sharing that!


Anyone willing to mix up a 5g bucket of tap water that has some phosphate and run some of this regenerated GFO on it for around 24 hours to see how effective it is at removing phosphate?

 

[Randy Holmes-Farley]

Here in EU "R-phrases" (http://en.wikipedia.org/wiki/List_of_R-phrases) go as follows:

0.5 M : R36/38 - Irritating
1.0 M : R34 - Corrosive
1.66+ M : R35 - Strongly corrosive

OK, the EU just has to be different.

That said, in the US corrosive generally means reactions with metals, not people. But it is certainly true that the stronger it is the more damage it will do to you.

 

[alanmorehead]

I forgot to mention that the samples for testing may require pH adjusting, especially the NaOH soak solutions. I know that the API test kit required the pH of the NaOH soak solutions to be adjusted down with acid until very little of bottle #1 (acid) was required to drive the pH low. You will need to use a PO4-free acid for this, so test a diluted acid sample for PO4 before doing this.
Scott

I got my phosphate test packets and picked up a bottle of NaOH today. Just wanted to clarify a few things before I do the tests:

- I assume the purpose of using vinegar is the low pH, which allows the calcium carbonate to dissolve since the pH is below ~6.5? Also, the only reason I am neutralizing the solution is to get an accurate PO4 reading? If so, then I will need to take an isolated sample of the vinegar/water mix, neutralize it, then test the PO4. Then the same thing after the GFO is soaked, right? I was planning on just using baking soda to neutralize it, since it is readily available and phosphate free. Sound good?

- On the NaOH side. I assume I need to do the same thing, neutralize and isolate, for testing the sample? If so, what do you recommend for neutralizing the NaOH solution?

Alan

 

[tatuvaaj]

- I assume the purpose of using vinegar is the low pH, which allows the calcium carbonate to dissolve since the pH is below ~6.5?

Yes

Also, the only reason I am neutralizing the solution is to get an accurate PO4 reading? If so, then I will need to take an isolated sample of the vinegar/water mix, neutralize it, then test the PO4.

I don't think you need to raise the pH of vinegar solution. AFAIK it is the high pH that is problem for PO4 test kits.

On the NaOH side. I assume I need to do the same thing, neutralize and isolate, for testing the sample? If so, what do you recommend for neutralizing the NaOH solution?

I use distilled vinegar. Mine is PO4 free but it doesn't matter much because there's going to be so much PO4 in the NaOH mix that little bit of PO4 in the vinegar is not going to show in the results


ps. I'm currently trying to see how long it takes to saturate the NaOH solution. After 60 hrs the PO4 is still rising :thumbsup: For once I wish I had *less* sensitive PO4 kit...