Regenerating GFO
- Thread starter tatuvaaj
- Start date
My regenrated GFO has been in the reactor for about 6 weeks now. I agree that it is darker than the fresh stuff. Also, agree that it is hard to rinse all of the NAOH off. Didn't get all of that "soapy" feeling to go away but put it in anyway. My system has been running undetectable (by Sailfert) phosphate since about two days after the regenerated GFO whet in.
Conditions in the display are excellent! No algae or cyano. I do clean the glass every two or three days. I see no negative impact on my ATS, solid growth and undetectable nitrates by the sensitive Sailfert test.
Plan to take it out on Wednesday and replace with fresh while I regenerate this batch. I think I'll hold on the GFO until Friday to see what happens. I am interested to see the effect of an equal amount of fresh GFO. However, there's nothing in the tank that hasn't seen phosphates over 0.5 so, in the interests of science, why not wait and see if my rock is still leeching beyond the ability of the ATS to absorb it.
Conditions in the display are excellent! No algae or cyano. I do clean the glass every two or three days. I see no negative impact on my ATS, solid growth and undetectable nitrates by the sensitive Sailfert test.
Plan to take it out on Wednesday and replace with fresh while I regenerate this batch. I think I'll hold on the GFO until Friday to see what happens. I am interested to see the effect of an equal amount of fresh GFO. However, there's nothing in the tank that hasn't seen phosphates over 0.5 so, in the interests of science, why not wait and see if my rock is still leeching beyond the ability of the ATS to absorb it.
GFO has been out of my system and in NAOH since Wednesday. I did not detected phosphates in my system using my Sailfert kit until this afternoon. Even now it's just a hint of blue. Everything in the "nitrogen family" remains undetectable.
However, my glass has needed cleaning daily since removing the GFO and I'm getting some thin green growth on some of the rock in the display. Also, I've had a small colony of red/brown flatworms all along. The flatworm population has jumped up and they are darker. They were light brown before and are now rust colored.
Last bit. My ATS has grown thicker than ever since I removed the GFO. The screens are very heavy and I need to clean them early.
Am going to put some fresh HC GFO back in in a bit. I think I'll start with about a third of what I had and see what happens.
However, my glass has needed cleaning daily since removing the GFO and I'm getting some thin green growth on some of the rock in the display. Also, I've had a small colony of red/brown flatworms all along. The flatworm population has jumped up and they are darker. They were light brown before and are now rust colored.
Last bit. My ATS has grown thicker than ever since I removed the GFO. The screens are very heavy and I need to clean them early.
Am going to put some fresh HC GFO back in in a bit. I think I'll start with about a third of what I had and see what happens.
solos2
New member
p.s. a little off-topic, but how do you use strontium nitrate for that purpose, and wouldn't that nitrate dissolve into the water, ie. BAD?
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So, what's the best recipe thus far to regenerate GFO? Just acid wash or acid, then base... or what? Thanks in advance...
+1
+1
badonkadonk
Member
I've been regenerating my GFO using NaOH pellets (dissolved in water, of course, to 1 M) several times by now. I first mix the spent GFO with about 3x the volume of GFO in a bucket and decant the liquid, then repeat 2 more times. I let the GFO sit in the second and third washes of hydroxide solution for a few hours each, and give it an occassional stir if I happen to be around. I don't know whether the GFO is porous that it takes a while to leach, but figure it can't hurt. Then I repeat the rinses with RO/DI water 3 or 4 times, and then pour the GFO into mesh nylon filter socks and hang them up to drip dry. Then I dip the filter socks into pitchers of RO/DI water a few more times (changing the RO/DI between soaks), allowing the water to drip out between each batch. I finish up by dipping the filter socks into tank water (saved from a water change) to buffer out any remaining hydroxide, and finally hit it with more RO/DI before I let it completely dry and pour it back into a container for storage. It may sound like a lot of work, but mostly it is just time spent soaking/draining and only takes a minute for each step. And the GFO doesn't have to be pre-rinsed next time you use it. Also I have a fair amount of GFO from various sources all mixed together - Phosban, the Dr. FosterSmith brand, BRS, etc., and do the batch of 5 or more pounds all at once. I bought the NaOH online, just do a Google search for it, I got mine from AAA-Chemicals.
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SWINGRRRR
Premium Member
I dont understand this statement.
joao junior
New member
if rowaphos can be regerate too??
AcroporAddict
There is no substitute.
It seems like you really shouldn't have to rinse the GFO as much as people seem to be doing here. GFO is non-porous from my understanding, so you are only rinsing the NaOH from the surface. Seems all you need to do is put the regenerated GFO in a filter bag and rinse a few times by dipping in tapwaster or RODI or run tapwater in thru the top of the bag and thru the GFO a couple times.
or am I wrong here?
or am I wrong here?
ScooterTDI
New member
I believe he is saying that he is using a volume of regeneration solution equal to 3 times the volume of the GFO he is regenerating, i.e 300 mL of solution for 100 mL of GFO.
Scott
ScooterTDI
New member
yes.
ScooterTDI
New member
Well, GFO is fairly porous, but I don't think the concern is necessarily NaOH, but rather getting all of the PO4 enriched solution out of the GFO.
Scott
ScooterTDI
New member
Personally, I think that the NaOH wash is unecessary. An acid wash will dissolve any precipitated CaCO3 as well as resurface the GFO.
Scott
AcroporAddict
There is no substitute.
I see. I just read Randy's article on it and he addresses internal surface area as well...thanks.
A simple acid wash followed by some tap water rinsing would be nice if it works.
jptenklooster
New member
Hello everybody,
I started this discussion in the BP discussion, but I think it is a good thing that Tatu made a separate one for everybody to follow. To answer some questions on how often you can regenerate the GFO. The producers of GFO have tested this and stopped testing after 10times regeneration. It was still 100% active. In my experience 30x is working as well (and going). I just have 2 badges of GFO, one in my tank and the other is regenerating in 1 M NaOH. I even reuse the NaOH solution 2x.
Furtheremore, GFO is Ironhydroxide/oxide mixture, so regeneration with vinegar will remove the phosphate but won't replace this with OH-. The advantage of having hydroxide bound to iron is that upon HPO4 binding (most commen form of PO4 in seawater) the released proton from the phosphate will interact with the hydroxide and will therefore not effect the pH in a negative way.
FeOH/O + HPO4 --> FePO4 + H2O
Good luck with saving money:beer:
I started this discussion in the BP discussion, but I think it is a good thing that Tatu made a separate one for everybody to follow. To answer some questions on how often you can regenerate the GFO. The producers of GFO have tested this and stopped testing after 10times regeneration. It was still 100% active. In my experience 30x is working as well (and going). I just have 2 badges of GFO, one in my tank and the other is regenerating in 1 M NaOH. I even reuse the NaOH solution 2x.
Furtheremore, GFO is Ironhydroxide/oxide mixture, so regeneration with vinegar will remove the phosphate but won't replace this with OH-. The advantage of having hydroxide bound to iron is that upon HPO4 binding (most commen form of PO4 in seawater) the released proton from the phosphate will interact with the hydroxide and will therefore not effect the pH in a negative way.
FeOH/O + HPO4 --> FePO4 + H2O
Good luck with saving money:beer:
ScooterTDI
New member
Its good to hear that you can get many regenerations out of GFO without losing activity.
I don't understand why you need NaOH to "replace" OH- on the surface of the GFO. The GFO already has OH- incorporated. By dissolving the surface with acid, you are exposing a fresh FeOH3 surface. There ought to still be FeOH3-on the surface of the GFO.
Scott
I don't understand why you need NaOH to "replace" OH- on the surface of the GFO. The GFO already has OH- incorporated. By dissolving the surface with acid, you are exposing a fresh FeOH3 surface. There ought to still be FeOH3-on the surface of the GFO.
Scott
