Bleach vs Acid

[chr15_8]

Do I need to anything else to neutralize the acid? All I have done is soak in the acid for 20 minutes.

Then I let them soak in RODI water for a few hours before rinsing/washing each rock in a tub of 25 litres (6.6 us gallons) RODI. I have put them into a container to soak in RODI water and changed it 5 hours ago (was in there for 24 hours). I will do the same thing again in another 19 hours tomorrow night.

Thanks
Chris

[bertoni]

The live rock will neutralize the acid by itself. A good rinsing is all that's needed.

[niqiri]

Just out of curiosity, why is acid effective at removing phosphate given that phosphoric acid has a pKa of about 3?

[Randy Holmes-Farley]

That's the reason, or part of it.

Phosphate binds to calcium carbonate surfaces as PO4--- or possibly HPO4--. H3PO4 won't bind at all, and I expect H2PO4-- binds fairly poorly. So lower pH reduces the portion of those things which bind.

Also, low pH will dissolve away the CaCO3 itself, releasing anything that is bound to it.


this has more detail:

Phosphate and the Reef Aquarium
http://reefkeeping.com/issues/2006-09/rhf/index.php

from it (and note the pKas are for seawater, not freshwater):




Figure 2. The structure of inorganic orthophosphate, with a central phosphorus atom (purple) and four oxygen atoms arranged in a tetrahedron. Three of the oxygen atoms can either have an attached proton (green) or be present with a negative charge on the oxygen atom (red). The amount present in each form in seawater varies with pH as indicated.

[niqiri]

I guess what I'm asking is why does acid work if the pKa of phosphoric acid is so low? I would think that the strong acid (HCl) would protonate all of the phosphate present and turn it into phosphoric acid, where it would dissociate back into H2PO4- and re-bind with the rock. I'm missing something somewhere, that much is clear. Also, how many acid baths and for how long are necessary? I soaked my rocks in hot tap water and HCl for a couple of hours, then put them into RO/DI to soak overnight with Lanthanum chloride to pull out any extra phosphate. Now I have added more acid and have waited about an hour. What should I do next?

[Randy Holmes-Farley]

One bath may be adequate, if you dissolve away the rock surface.

The reason acid works at all is exactly because it forces protonation of phosphoric and carbonic acids. Phosphoric acid does not reform the stronger binding forms (HPO4--and especially PO4---) as long as it is acidic. So you wash that away.

In acids, the rock will be bubbling away, removing the outer surface, as carbonate and bicarbonate are protonated to CO2, which bubbles off.

Additionally, phosphoric acid will not bind to calcium carbonate surfaces because it is mostly or fully protonated. This slide from the scientific literature shows the pH dependence of phosphate binding to aragonite. It does not need to be very acidic to reduce binding substantially:

http://yyy.rsmas.miami.edu/groups/jm...er1/sld013.htm

[niqiri]

Ok, so I took the rocks out of the RO/DI acid bath that they had been in all day. Then I scrubbed them manually (there was some brown material on them, and even a little algae), then poured HCl over each one. The plan is to now put them in another RO/DI bath with lanthanum chloride and then neutralize with sodium bicarbonate. Does this sound like a good plan? I still have the other half of my rocks to bathe in acid, so should I use a different procedure?

[Randy Holmes-Farley]

I don't know if the lanthanum is useful or necessary, but that plan is probably OK. I'm not sure how much lanthanum might bind onto the freshly exposed rock.

Be sure to rinse well to remove loose lanthanum carbonate detritus.

[niqiri]

One last question for you: Does it matter if I rinse them with tap water? Will this change the environment from acidic to basic and allow the phosphate to reattach?

[Randy Holmes-Farley]

If there is phosphate or maybe silicate already in the tap water, that's an issue. Otherwise, its not a big concern. I might use tap.

[percula99]

I read through this entire post and decided to give it a shot. Previously I cooked my first 125 pounds of LR and it took 5 months to get it to where I put it in my DT. I had another 125 pounds and did not want to wait another five months. I put it in a rubbermaid garbage can with a 1/10 bleach/RO water combination for two days. I did two rinses in RO with dechlorinator. I then put it in 100% vinegar. It fizzed like alka seltzer for about 90 minutes and then slowed down. I left it overnight and the next day there was brown foam at the top of the vinegar. I put the rock in RO water with baking soda twice, then again with just RO. I then rinsed it by swishing it around in clean RO in small buckets, changing the water as it got milky. That is four RO rinses so far. It is now sitting on my back deck drying out until the wekend. It smells like the ocean now, no trace of bleach, and only a couple of very pourous rocks have a trace of vinegar smell. I plan on rinsing once more in RO an re-scaping my DT with the previously cooked 125 pounds and letting it all re-seed. Corals will be going in this weekend also and my fish are in QT for a few more weeks as I bought two new ones. I am confident this will work out fine because of all the effort I put in and how the rock does not smell bad anymore. Any thoughts from anyone would be appreciated.

[niqiri]

Now that I'm soaking my rocks, should I put a heater in the bins? Will this increase phosphate leaching into the RODI?

[cjtabares]

I gave my rock a bleach bath for about 48 hours then rinsed it let it dry rinsed it again untill it no longer smelt like bleach. Today I gave it a 20 min bath in murric acid and it went ok. Some of my rock has some brown on it that seems to be part of the rock, is this rock ok to use? Here is a pic of a small piece with some of the brown on it.

[Randy Holmes-Farley]

Unless the rocks are very cold, I wouldn't bother heating them.

[percula99]

Originally Posted by Randy Holmes-Farley

Unless the rocks are very cold, I wouldn't bother heating them.

Randy, I live in Canada and it is still cold here. Tonight it is going down close to freezing. I have my rock drying out on the back deck and seeing as it is dead after the bleach and vinegar I really did not see an issue with leaving it out there. I plan on bringing it in Friday evening to warm up before I re-scape my tank on Saturday. Do you see an issue with this?

[Randy Holmes-Farley]

No, that sounds fine.

[percula99]

When I put my cooked LR in the tank (first 125 pounds), about two weeks ago, I have not suffered through any algae outbreaks. I will be putting in my bleached and acid washed rock (2nd 125 pounds) this weekend and completely rescaping the tank. Can I expect an algae outbreak on this rock?

[bertoni]

Most setups see at least a bit of an algae bloom. It should be fairly minimal with this batch of rock, assuming that the treatment removed a lot of the organic debris.

[banzai75x]

Is muriatic acid diluted at 10 parts to 1? Use 10 gallons of RO water to 1 gallon of acid? I've seen different numbers on this thread and just wanted to make sure.

[Randy Holmes-Farley]

That's what I would recommend yes.

[Genj]

It would be nice to have a message board software that had a 'thread summary sticky' that would act like a wiki on threads that grow in size, but contain good info spread out across many pages.

So in summary, to have clean rock follow this HIGHLY unscientific method:

1 part bleach to 10 parts water, soak for 24-48 hours, checking for diluted strength over time.

1 part acid to 10 parts water, soak for at least 2 hours?

Rinse in RO with dechlorinator a few times

Rinse in RO

Dry out in the sun for a 7 day period

Viola?

Please correct where I'm wrong if you so choose.

[bheron]

Banzai75x - thats what I always used 10 parts water to 1 part acid.

Genj - thats the gist of it. Every now and then I put out a summary update of what we've all learned. Im not sure how scientific or unscientific this should be, but I will choose to correct you a bit tho -

- bleach can be stronger IMO than 10:1. I've usually done 3:1.

- acid soaking time varies, depending on how much phosphate you have on your rock. and know way of measuring that as far as I know. First time i soaked for 30-60 seconds and it dint work. Last time I soaked for 30 mins and I've recently learned that didnt work. No idea if soaking longer will work either.

- simple rinse in RO and let soak in the sun until it doesnt smell. Really the acid will get rid of the chlorine when its dipped.

[percula99]

Well I went through this process and re-scaped my tank a week and a half ago and I am completely satisfied with the outcome. I was a little apprehensive about using the acid so I opted for staight vinegar. I went to Costco and bought 12-4 liter (1 gallon) jugs and soaked the rock in the vinegar overnight and did five rinses in RO, two rinses with dechlorinator. I checked it against the rock I had cooked previously and both smelled just like the ocean.

[Genj]

Thanks for the information and update to the summary Bryan!

[bheron]

I really hope to do a full update shortly. My most recent attempt has failed so it would be good to document what we've all learned on here. Hey....maybe I'll do it now?