Regenerating GFO

[elijaher]

+1 contains sodium hydroxide I would'nt take that change.

 

[mike810]

ya i wont risk it. I'll go to lowes when i get the chance. was looking for the one pictured in the link but grabbed this one instead cause i had some clogged drains anyways

 

[mike810]

I am about ready to try and recharge some GFO. I just want to get some clear cut info before I take the plunge. I have about 1 Cup of HC GFO from BRS. How much NaOH should I use? I know you guys say 40Grams to 1 liter of water or "1M" . How much should I use to treat 1 Cup of HC GFO? THANKS

 

[tmz]

I'd use three to five times the volume of the gfo. So ,say 4 cups of water or 32 oz( assuming an 8 oz cup) which is about a liter and then 3 tbspoons of sodium hydroxide which is about 40 grams. If you haven't already done so, I'd soak in vinegar overnight first.

 

[mike810]

so basically 1m for 1 cup of hc gfo? I'm about to go soak it in some vinegar right now... Do i have to rinse off the vinegar before i add the sodium hydroxide?

 

[tlwong]

Correct me if I am wrong . The purpose of using hydroxide is to raise the pH so as to dissolve the ferric phosphate resulting in a final product of ferric oxide.

If this is the case can we use potassium hydroxide instead ?

 

[elijaher]

Does koh cost more?

 

[tlwong]

Does koh cost more?

In my area it is easier to get KOH than NaOH.

 

[Matt_Wandell]

Tatu, great thread. Maybe I missed it but what type of GFO are you using? Anybody else using actual granular product (not pellet) and seeing problems with the media melting away?

 

[Matt_Wandell]

Has anybody tried presoaking the GFO in dilute muriatic acid rather than vinegar? What dilution did you use?

Just trying to figure out how I'll be able to easily and cheaply do this with 40USG of GFO every month...

 

[elijaher]

Muriatic acid will but little to powerful it will brake down it more.

 

[SimonSKL]

Has anybody tried presoaking the GFO in dilute muriatic acid rather than vinegar? What dilution did you use?

Just trying to figure out how I'll be able to easily and cheaply do this with 40USG of GFO every month...

I did use muriatic acid in 3% concentration (regular MA is about 31%) to presoak my BRS pelletized GFO and measured the PO4 level of the final solution. The purpose of presoaking the GFO in vinegar or muriatic acid is to remove any carbonate build up on the surfaces of the GFO. However, during my presoak process, I did not notice any effervescent or bubbling and the PO4 level is 0 ppm. I concluded this process really did not accomplish anything and now I am skipping the acid presoak step.

 

[Matt_Wandell]

I did use muriatic acid in 3% concentration (regular MA is about 31%) to presoak my BRS pelletized GFO and measured the PO4 level of the final solution. The purpose of presoaking the GFO in vinegar or muriatic acid is to remove any carbonate build up on the surfaces of the GFO. However, during my presoak process, I did not notice any effervescent or bubbling and the PO4 level is 0 ppm. I concluded this process really did not accomplish anything and now I am skipping the acid presoak step.

Thanks Simon,

So to verify your numbers, did you dilute muriatic acid in a 10:1 ratio? Any noticeable dissolution of the GFO granules?

I imagine whther or not the presoak is necessary depends on a lot of factors that change from system to system but it's interesting you didn't notice any bubbling at all.

 

[tmz]

I did use muriatic acid in 3% concentration (regular MA is about 31%) to presoak my BRS pelletized GFO and measured the PO4 level of the final solution. The purpose of presoaking the GFO in vinegar or muriatic acid is to remove any carbonate build up on the surfaces of the GFO. However, during my presoak process, I did not notice any effervescent or bubbling and the PO4 level is 0 ppm. I concluded this process really did not accomplish anything and now I am skipping the acid presoak step.


Obviously if you don't have calcium carbonate precipitation in a particular system the acid bath is uneccessary, Many do need it,however, to remove precipitant from the surface of the gfo before the soak in lye.. The acid bath will not remove PO4.

 

[Claes]

Great thread!

For those of us who are using aluminum-based phosphate removers, will the sodium hydroxide treatment regenerate such materials as well?

 

[SimonSKL]

Thanks Simon,

So to verify your numbers, did you dilute muriatic acid in a 10:1 ratio? Any noticeable dissolution of the GFO granules?

I imagine whther or not the presoak is necessary depends on a lot of factors that change from system to system but it's interesting you didn't notice any bubbling at all.

Sorry Matt, forgot to answer your question. Yes, one part muriatic acid and 9 parts water will give you ~3% hydrochloric acid. While I didn't notice any significant dissolution of GFO in 3% HCl, the dissolution is significant in 1M NaOH. I now use 0.5M NaOH (20g in 1 L of water) which seems to be better. BTW I use BRS high capacity GFO which is a little harder than the granular or pelletized GFO.

 

[paraletho]

Yes Simon we are on our 5th regeneration and the hi capacity is still usable but getting pretty fine. We are switching to .5M. I have had no problems with the GFO doing its job or side effects from the process.

 

[Matt_Wandell]

So how are you folks handling the GFO to do the regen process? Are you removing it from the reactor and putting it in a bucket?

This is something I tried today, it's 2g of 0.1M NaOH solution recirculating through a BRS reactor. I figure I can just keep this unit as my "lye reactor" and rotate out the canister portion without ever needing to touch or remove the GFO. I have no idea how this will affect the acrylic or pump, but we'll see...

 

[Matt_Wandell]

Sorry Matt, forgot to answer your question. Yes, one part muriatic acid and 9 parts water will give you ~3% hydrochloric acid. While I didn't notice any significant dissolution of GFO in 3% HCl, the dissolution is significant in 1M NaOH. I now use 0.5M NaOH (20g in 1 L of water) which seems to be better. BTW I use BRS high capacity GFO which is a little harder than the granular or pelletized GFO.

Thanks Simon. It is tough to figure out if a 9:1 dilution of full strength (37%) muriatic acid should be called 10% or 3.7%.

 

[Matt_Wandell]

So we have an interesting snag on our usage of NaOH solution--anything above pH 11 needs to be neutralized before going down our drains.

Can somebody verify that I'm doing this math correctly? For every 40g of 100% NaOH added to a solution I've calculated that I would need to add 83 mL of full strength (37%) muriatic acid to completely neutralize it. Sound right?