Sodium Hydroxide ruining my pump?

[bheron]

Hi,
I'm having a real problem here with my pumps. I've been using a process to regenrate my Granular Ferric Oxide (GFO) using a mix of Sodium Hydroxide and water (see link to this article http://www.advancedaquarist.com/2010/10/chemistry).

My problem is, I think the Sodium Hydroxide might be ruining my little maxi jet pump I use in this regenerating process. I basically use the pump to push the Sodium Hydroxide mix through the GFO for 3-4 days. Well, I've now been through 3 maxi-jets. The first two I thought maybe defective product, maybe it the chemical. Now a brand new maxijet has failed while I was regenerating GFO.

So question is: can Sodium Hydroxide ruin a pump?

Maybe a question for the chemistry forum?

[disc1]

Hi,
I'm having a real problem here with my pumps. I've been using a process to regenrate my Granular Ferric Oxide (GFO) using a mix of Sodium Hydroxide and water (see link to this article http://www.advancedaquarist.com/2010/10/chemistry).

My problem is, I think the Sodium Hydroxide might be ruining my little maxi jet pump I use in this regenerating process. I basically use the pump to push the Sodium Hydroxide mix through the GFO for 3-4 days. Well, I've now been through 3 maxi-jets. The first two I thought maybe defective product, maybe it the chemical. Now a brand new maxijet has failed while I was regenerating GFO.

So question is: can Sodium Hydroxide ruin a pump?

Maybe a question for the chemistry forum?

I haven't read the article and don't really have time to hunt through it. How concentrated is the sodium hydroxide solution being used here? How are the pumps failing?

Highly concentrated solutions of hydroxide are extremely corrosive. They can definitely damage a pump housing given a little time.

I agree that this might do better if you move it to the chem forum. Click the link (little white and red triangle below your avatar) to report your post and you can ask a mod to move it.

[bheron]

thanks so much!


How concentrated is the sodium hydroxide solution being used here?


- I'm mixing 454mg of it with 3 gallons of water.


How are the pumps failing?


- Its strange. they're still getting power. and if i open the housing i can get the impeller to turn, sometimes. but when i put it back together it doesnt push any water.


Highly concentrated solutions of hydroxide are extremely corrosive. They can definitely damage a pump housing given a little time.


- wow thats what I was wondering. first two pumps it didnt fail right away. the other night with a very new pump it stopped in a few hours. i might've used more than the 454mg too.


Click the link (little white and red triangle below your avatar) to report your post and you can ask a mod to move it.

- wow, awesome. never knew that.

ok will do, thanks for this guidance. need to figure this out before re-ordering a new pump.

[dc]

[moved]...

[disc1]

Less than half a gram in three gallons shouldn't be enough to hurt a pump. That's not very concentrated at all. You can fit upwards of 400g per liter on NaOH.

I wonder if the GFO is dissolving to some small extent and depositing on the pump shaft. Do you see any brown gunk around the impeller or anywhere?

[bheron]

hmmm, thanks. i dont see anything on the pump shaft ever. its a real simple pump. each time i open the cover, remove the impeller shaft, clean out the impeller "well". Never see anything. First time I assumed a bad pump or shaft and the MFR sent me a new shaft. Didnt help. 2nd and 3rd time i just got a new pump. Each time I pull out the impeller, clean it and the well, drop it in and turn it on. sometimes i have to tweak it but eventually it turns. but in other cases the motor vibrates but the impeller doesnt turn.

I have to think its somehow related. but maybe its not? just want to be sure before i drop another $25 on these little pumps.

[animalkingdom]

The NaOH wont be harmful to your pump at that concentration. Its more likely the gfo sediment or something else entirely

[bheron]

Ok that's good to know. Maybe just Bad luck with pumps? I'm gonna try to turn these in for warranty coverage and see if that helps. Or maybe keep researching the problem.

[disc1]

Maybe just Bad luck with pumps?

This may well be the case. What brand of pumps are we talking about?

[dkeller_nc]

What you're using for a concentration of NaOH is far below what the article recommends (the article recommends about 1M NaOH). Generally speaking, sodium hydroxide isn't corrosive to metals, but it can be a real problem with certain plastics and ceramics.

If I were to guess, and based on the symptoms you report, I'd think that the sodium hydroxide is attacking the seal between the power cord and housing, allowing sodium hydroxide into the pump's coil. The NaOH then attacks the insulation of the windings of the coil, causing it to short. This is the classic failure mode for electrical motors (shorted windings), and the effect is a motor that doesn't turn the rotor, or turns it very slowly, and gets really hot.

I would think if you were getting particulates into the rotor well, you'd notice that the impeller would be very hard to turn by hand. Another possibility would be if the PH had a ceramic central shaft, which can be attacked by NaOH, albeit generally at a much higher NaOH concentration than you're using.

One way around this would be to use a peristaltic pump - the neoprene or santoprene tubing that generally comes with them should be impervious to even a reasonably high concentration of NaOH (20%). Just don't use silicone tubing.

[bheron]

David, I've been using maxi jet 1200s

Dkeller - that's interesting stuff. I'll have to check but I thought I was using the right dose. I take 3 gallons of water and mix in half a bottle of Roebick crystal drain opener. I think they are 902mg bottles of which I dump half.

Anyway, I'll have to look into those peristaltic pumps and see if I can get one at a good price that would pump the solution through. Checking eBay now...

[disc1]

OK, we've got a unit issue here. 902mg is 902 milligrams. That's less than a gram. That's teaspoon quantity round abouts. I don't see anyone selling a bottle that small of drain cleaner. So you must be getting something confused.

Is it 902g as in grams? That's right at 2 pounds. If you're adding half of that then you're adding roughly 10 moles of NaOH to roughly 12 L of water for something on the order of 1M. That may indeed be enough to do some of the types of corrosion that dkeller was talking about a couple posts up.

[dkeller_nc]

Is it 902g as in grams? That's right at 2 pounds. If you're adding half of that then you're adding roughly 10 moles of NaOH to roughly 12 L of water for something on the order of 1M. That may indeed be enough to do some of the types of corrosion that dkeller was talking about a couple posts up.

Yep - I was wondering about that. The article mentioned 1M NaOH. I did find the article interesting, it does make sense that one could potentially force phosphate out of the material by swamping it with OH. But it does seem in the article that there's a really excessive amount of NaOH solution used for regeneration - far in excess of what I'd use to regenerate an ion-exchange chromatography column. Kind of wonder if that's because of channeling effects in the less-than-ideal reactor the author was using to hold the media.

[Mikefromaz]

Ok that's good to know. Maybe just Bad luck with pumps? I'm gonna try to turn these in for warranty coverage and see if that helps. Or maybe keep researching the problem.

Bryan, why not let the next pump run in plain water for a while before putting it into chemical use? I have found that maxijets are pretty reliable, including the one I have in my bird bath fountain. Between the dust storms here in AZ and the mess the birds make, at times the fountain looks more like a chemical slurry, but the pump keeps hanging in there (two years now). It might well be that there is a batch of bad pumps too. You could try changing brands too.

[tmz]

Maxi jet has changed . The manufacutring operations have moved . Cobalt pumps are now manufactured by those that made maxi jets. I've used a newer maxi jet without trouble but some have cmplained abut vibration and questioned it's reliability compared to the cobalt.
In any case,it doesn't sound like seals to me since the motor keeps running when submersed . Typically when a seal goes(as they do with some frequency in hydor korillia) pumps after acid baths ime), the motor shorts out when it's placed in water.
Personally,fwiw, I regenerate BRs HC gfo( it doesn't melt away or grind up very much compared to less dense gfo products) frequently but don't use a reactor ;just a plastic coffee can ,hand stirred a few times per day. The concentration is 3 tablespoons, about 45 g per 500ml . Solution at 5x the gfo quantity.

FWIW, food grade sodiaum hydroxide is easy to get at reasonable prices on line; it's popular in the soap making hobby. AAA chemicals is a good source.

[bheron]

David - LOL, you're right. I looked in my spreadsheet to be sure and it has "mg" there. but on the bottle its grams. So yes, 454 grams to 3 gallons of water.

dkeller - thanks. im not even a novice chemist so i'm following the article to the letter. now way of knowing for sure if it works but I have a hunch it might have regenerated the GFO. thanks for the pointers. will see if i can get a simple peristaltic pump to do the regen work maybe.

mikefromaz - well, this pump runs my GFO and Carbon reactor normally in the saltwater tank. do you still think a FW run would help?

Tom - I've been thinking about it and i really have had different results. sometimes the pump runs a little, sometimes its dead. so i guess in the end its hard to say what the cause was for each of the 3 situations.

Tom, also, thats great feedback. The article does say you dont need a pump to circulate during the regen, but i figured it would do a better job. maybe i just shouldnt use one at all. As far as the food grade stuff, I paid about $16 for 902g of the roebic. compared to the food grade one by AAA for $7 thats a big difference in price. whats the difference between the two? is it not as powerful?

[dkeller_nc]

Personally, I would use Tom's method. In theory, doing a batch regen would not be as effective as passing a solution through a packed bed as suggested by the AA article. But by using a really high NaOH concentration, the difference would be negligible.

And as far as safety, putting a quart or two of 1M NaOH in a plastic container with the GFO and letting it set for a day or two is a heck of a lot safer than pumping (pressurizing it) through a pump. Getting accidentally sprayed by saltwater with a powerhead can really sting if you get it in your eyes (DAMHIKT). But getting sprayed with 1M NaOH is another thing altogether.

By the way, from an effectiveness and efficiency perspective, the ideal way to regenerate any particulate media is to make a simple packed-bed column from a piece of 1-1/4" PVC pipe, a bit of floss in the bottom, and some airline tubing fittings so that the regeneration liquid completely wets and covers the entire column of media to be regenerated. The driving force for moving the regen liquid through the column is the draining of it through the bottom fitting equipped with a 2-3 foot piece of tubing hanging into a bucket on the floor. The top fitting is air-tight, and pulls fresh regen solution from a reservoir by siphon action.

This is essentially old-school, low-pressure preparative chromatography, and it works exceedingly well from the standpoint of stripping all of the adsorbed chemical species off of the particulate media.

[tmz]

I think the difference is one is packaged as a drain cleaner and the other is packaged as generic chemical.I doubt there is a difference in strength. I know the AAA is claimed to be food grade and is used by folks who make soaps as a hobby.

[Mikefromaz]

David - LOL, you're right. I looked in my spreadsheet to be sure and it has "mg" there. but on the bottle its grams. So yes, 454 grams to 3 gallons of water.

dkeller - thanks. im not even a novice chemist so i'm following the article to the letter. now way of knowing for sure if it works but I have a hunch it might have regenerated the GFO. thanks for the pointers. will see if i can get a simple peristaltic pump to do the regen work maybe.

mikefromaz - well, this pump runs my GFO and Carbon reactor normally in the saltwater tank. do you still think a FW run would help?

Tom - I've been thinking about it and i really have had different results. sometimes the pump runs a little, sometimes its dead. so i guess in the end its hard to say what the cause was for each of the 3 situations.

Tom, also, thats great feedback. The article does say you dont need a pump to circulate during the regen, but i figured it would do a better job. maybe i just shouldnt use one at all. As far as the food grade stuff, I paid about $16 for 902g of the roebic. compared to the food grade one by AAA for $7 thats a big difference in price. whats the difference between the two? is it not as powerful?
No I don't believe a fresh water run would fix anything. I was thinkng more in terms of sniffing out a bad pump before using it for your purpose. It may very well be the maxi just isn't cutting it.

[bheron]

Personally, I would use Tom's method. In theory, doing a batch regen would not be as effective as passing a solution through a packed bed as suggested by the AA article. But by using a really high NaOH concentration, the difference would be negligible.

And as far as safety, putting a quart or two of 1M NaOH in a plastic container with the GFO and letting it set for a day or two is a heck of a lot safer than pumping (pressurizing it) through a pump. Getting accidentally sprayed by saltwater with a powerhead can really sting if you get it in your eyes (DAMHIKT). But getting sprayed with 1M NaOH is another thing altogether.

By the way, from an effectiveness and efficiency perspective, the ideal way to regenerate any particulate media is to make a simple packed-bed column from a piece of 1-1/4" PVC pipe, a bit of floss in the bottom, and some airline tubing fittings so that the regeneration liquid completely wets and covers the entire column of media to be regenerated. The driving force for moving the regen liquid through the column is the draining of it through the bottom fitting equipped with a 2-3 foot piece of tubing hanging into a bucket on the floor. The top fitting is air-tight, and pulls fresh regen solution from a reservoir by siphon action.

This is essentially old-school, low-pressure preparative chromatography, and it works exceedingly well from the standpoint of stripping all of the adsorbed chemical species off of the particulate media.

Very cool! Great suggestions.

I was away for the weekend but before I left I simply emptied may canisters of GFO into the bucket of NaOH and solution I was mixing with. I stirred it once before I left and a couple times since coming home.

So couple questions:

1) whats the suggested high concentration of NaOH I should use?
2) how long should I do this? how often to stir?
3) how do I know if it worked (might not be an answer here)?

I like the idea of the old school method, only if its just another cool thing to learn.

[dkeller_nc]

1) Start with the article's suggested 1M NaOH strength. To be effective, particularly as a batch-regen method (as opposed to the chromatography column that I described), you must get the concentration high enough to overcome the association constant for ferrous phosphate. That can actually be calculated, but it's easier to just swamp the heck out of the exhausted media.

2) Chemical equilibration will be very quick - measured in seconds if not shorter. What takes time is the physical process of diffusion. If you've a solid media like BRS's high-capacity GFO, I'd let it go overnight, or in a pinch, maybe an hour. If you're using the large-particle agglomerated GFO, you might want to wait 24 hours. Stirring really shouldn't even be necessary, though it won't hurt - a half-hearted once around the perimeter of the vessel a couple of times should be more than enough.

3) A couple of ways come to mind - test the regen NaOH for phosphate. I'm not sure whether phosphate tests designed for aquarium use would even be suitable for this purpose, you might have to dilute the NaOH and/or neutralize it to be able to test it. You would simply go through a couple or three cycles of NaOH - the first one should have the majority of the phosphate in it, the second one, less so, etc... The other way is more of experiment - make up a solution of sodium phosphate of a known concentration, weigh a sample of the regened media, and calculate what the sample's capacity for adsorption is.

Or, you could just rinse the media, call it "good enough", and go have a beer. ;)

[bheron]

1) Start with the article's suggested 1M NaOH strength. To be effective, particularly as a batch-regen method (as opposed to the chromatography column that I described), you must get the concentration high enough to overcome the association constant for ferrous phosphate. That can actually be calculated, but it's easier to just swamp the heck out of the exhausted media.

- Ok cool.


2) Chemical equilibration will be very quick - measured in seconds if not shorter. What takes time is the physical process of diffusion. If you've a solid media like BRS's high-capacity GFO, I'd let it go overnight, or in a pinch, maybe an hour. If you're using the large-particle agglomerated GFO, you might want to wait 24 hours. Stirring really shouldn't even be necessary, though it won't hurt - a half-hearted once around the perimeter of the vessel a couple of times should be more than enough.


- I use the high capacity GFO. Its been "soaking" since Friday. Hope thats not a bad thing. Will rinse thoroughly with RO tonight then. Hope I didnt ruin it.



3) A couple of ways come to mind - test the regen NaOH for phosphate. I'm not sure whether phosphate tests designed for aquarium use would even be suitable for this purpose, you might have to dilute the NaOH and/or neutralize it to be able to test it. You would simply go through a couple or three cycles of NaOH - the first one should have the majority of the phosphate in it, the second one, less so, etc... The other way is more of experiment - make up a solution of sodium phosphate of a known concentration, weigh a sample of the regened media, and calculate what the sample's capacity for adsorption is.

Or, you could just rinse the media, call it "good enough", and go have a beer. ;)

- :) Thats my style.

Well, thanks so much for the insight here. I think I need to spend alot more time in this particular forum.

I have yet another brand new maxijet pump I will use solely to filter through my GFO reactor. And then will just use the method described here to regen. And finally will be trying to get warranty support on my last two maxi jets.

Oh, the article I referenced mentioned possibly getting @ 9 regen cycles out of a batch of GFO. Is there any rule of thumb anyone's aware of?

[dkeller_nc]

-Oh, the article I referenced mentioned possibly getting @ 9 regen cycles out of a batch of GFO. Is there any rule of thumb anyone's aware of?

I'm not aware of any rule-of-thumb for the regen of GFO, but I would think that at some point either the particles will get too small from being partially dissolved by the acid treatment, or coated with stuff from the tank that the acid and NaOH treatment won't remove. Might be interesting to take a picture with a magnification lens of the individual particles when new, and then after a few regen cycles.

[bheron]

ok thanks.