Leaching perilite?

[Exo]

I just read an interesting article on experiments done with neps and I noticed something odd.....apparently perlite leaches harmfull salts.

http://carnivorousplants.org/cpn/samples/v33n1p26_31.html

The salts apparently can be removed by soaking it in water that has a high conductivity, but my question is......

How the heck do you make water more conductive?

If anyone knows let me know.

Thanks

 

[vraev]

Generally conductivity and ionic concentration goes hand in hand. Afterall, conduction is the movement of charged particles. So, you can make a liquid more conductive by adding any sort of salt in it. Atleast thats what I would think.

 

[ch00ka]

I've read somewhere that some sources of perlite can release fluoride among other things, but I've never had a problem using it out of the bag . I wet it down to avoid inhaling the dust and flush the pot once to settle the plant into it's new media. The study you cite deals with seeds and seedlings which are probably more sensitive to salts and other dissolved solids leaching out of perlite or any other media components.

 

[mobile]

For approximately 18 months I have had a small planted tank containing Cephalotus cuttings, Heliamphora minor, Nepenthes glabrata and Utricularia sandersonii, all growing in perlite, with a top dressing of live Sphagnum moss. The perlite is the growing medium and I have not had any issues with it. However, as perlite is a natural(ish) resource, there will be variations within its properties.

 

[Exo]

So You basically soak it in saltwater for a few days and then soak it in distilled or rainwater?

 

[vraev]

Hmm...see...I would think about it in this way.

Consider that the perlite has a particular kind of salt....(Magnesium afaik). You need a hypotonic solution in magnesium to have diffusion work its magic. THe best way to do this is to have a stirrer that constantly stirs the suspension of perlite. Maximum surface-area/liquid exposure.

See... water has low conductivity to begin with. Lets take the principal of a galvanic cell. You use a salt bridge to prevent the buildup of a particular ion in high concentrations that can prevent current flow. So, I would think the whole idea of soaking perlite in high ionic solution is counterproductive, as your solution will have too much postive charge (Na+) to soak up any Mg2+ ions.

So IMO...the best way to leech out ions is to put it in as pure water as you can.

But.... comes back to the point of doing this. Are u doing this for seeds or seedlings? Because apart from those handful of holy grail ultrahighland species...many are tolerant of these low salts.

 

[Exo]

Hmm...see...I would think about it in this way.

Consider that the perlite has a particular kind of salt....(Magnesium afaik). You need a hypotonic solution in magnesium to have diffusion work its magic. THe best way to do this is to have a stirrer that constantly stirs the suspension of perlite. Maximum surface-area/liquid exposure.

See... water has low conductivity to begin with. Lets take the principal of a galvanic cell. You use a salt bridge to prevent the buildup of a particular ion in high concentrations that can prevent current flow. So, I would think the whole idea of soaking perlite in high ionic solution is counterproductive, as your solution will have too much postive charge (Na+) to soak up any Mg2+ ions.

So IMO...the best way to leech out ions is to put it in as pure water as you can.

But.... comes back to the point of doing this. Are u doing this for seeds or seedlings? Because apart from those handful of holy grail ultrahighland species...many are tolerant of these low salts.

I was going to try growing my small burbidgeae in a mix similar to the one found to work best in the study.

 

[vraev]

Dude...I grow a burbidgeae 2-3 inches diameter in a mix with perlite/orchid bark/LFS and charcoal. The plant is doing fine. I personally wouldn't worry about using regular perlite.

 

[Av8tor1]

Interesting....
Way, way out of my league here but I think I see the what they are getting at. If whatever you are trying to remove has such a bond that pure water will not remove it then would a cation/anion exchange work? You soak in something that would exchange the original offending ions for something that the pure water will then more easily remove

umm I think LOLOLOL

 

[Exo]

Dude...I grow a burbidgeae 2-3 inches diameter in a mix with perlite/orchid bark/LFS and charcoal. The plant is doing fine. I personally wouldn't worry about using regular perlite.

Ok then, I'll probably just soak the perlite in distilled for a day and stir it a few times just to be sure though. I've never really heard of people having problems with seedlings before due to conductivity, perlite minerals, having to use fungicides, Ect, so I was kinda surprised when I read the study.

 

[justjack]

Hmm...see...I would think about it in this way.

Consider that the perlite has a particular kind of salt....(Magnesium afaik). You need a hypotonic solution in magnesium to have diffusion work its magic. THe best way to do this is to have a stirrer that constantly stirs the suspension of perlite. Maximum surface-area/liquid exposure.

See... water has low conductivity to begin with. Lets take the principal of a galvanic cell. You use a salt bridge to prevent the buildup of a particular ion in high concentrations that can prevent current flow. So, I would think the whole idea of soaking perlite in high ionic solution is counterproductive, as your solution will have too much postive charge (Na+) to soak up any Mg2+ ions.

So IMO...the best way to leech out ions is to put it in as pure water as you can.

But.... comes back to the point of doing this. Are u doing this for seeds or seedlings? Because apart from those handful of holy grail ultrahighland species...many are tolerant of these low salts.

Ummmmm, yeah. You could also just say to get salt out, it would be stupid to put salt in first.

If it really matters to you, if you want to take the extra precaution, soak the perlite in a bucket of the purest water you can get your mitts on for a day or two. Oh, stir occasionally and set on 425.. just kidding about the 425.

 

[vraev]

Interesting....
Way, way out of my league here but I think I see the what they are getting at. If whatever you are trying to remove has such a bond that pure water will not remove it then would a cation/anion exchange work? You soak in something that would exchange the original offending ions for something that the pure water will then more easily remove

umm I think LOLOLOL

Actually B..that works. You are right...but once again there....u need to first add salt to pure water to make it conductive. So then...u can use it as an electrolytic solution. But what I would think is that those ions will be replaced by other ions frm solution. The charges have to be neutralized in perlite itself.

 

[caesium]

If you really want to go through the trouble, you can try precipitating the magnesium out with NaOH, as Mg(OH)2 is rather insoluble. But then you need to bring the pH back down afterwards and get rid of the sodium ions. I don't think fluoride is the problem because if both Mg and F are present, the combined MgF2 is very insoluble and shouldn't pose a problem to anything.

I really don't think any of that is necessary though. Neps really aren't that sensitive for the most part, and you could always use pumice instead if you are still worried.

 

[The Griffin]

I think the stuff about perlite is the same stuff that applies to sand.
Perlite is used for a variety of things, and the stuff we are generally buy, says "Horticultural" on it. Perlite can also be used for insulation, filtration and other things.
So, your horticultural perlite is good to use. Most people wash their sand(many will say even wash the play sand that says "Washed and screened" on it).
I have used perlite out of a bag many times, but when I have time, I will soak in a bucket of pure water, stirring occasionally, for at least a day. Then I will put it in a fine net or pasta strainer and run pure water over it until it runs clear.
If you are worried about getting particles out of it, change the water and soak for another day, and that should get anything you might think is in there out.

Regards,

Joe

 

[Est]

The salts apparently can be removed by soaking it in water that has a high conductivity, but my question is......

This sounded funny to me so I went ahead and skimmed the pertinent parts of the article... I can't seem to find where the author suggests using conductive water to aid in leaching. In fact, the paragraph that I read suggested (the more-logical) opposite. The author writes:

Perlite was added to purified water (two parts water to one part perlite) and the conductivity of the water increased more than threefold, over a two day period.

This merely indicates that the perlite is leaching ions. In general, if you want to remove salts, you want to use as "pure" water as you can (simply to facilitate diffusion). The only reason to use a solution of water that is highly conductive would be for ion exchange. And then you'd need to worry about whatever ion you're exchanging for...

So unless I'm missing something, I think that you may have misinterpreted the author.

If I am missing something, the most logical reason I could come up with would be making the water more conductive by lowering the pH. This would let a rinse mimic the in-media conditions so that there's hopefully nothing left for protons that were added experimentally (via tannic, fulvic, and humic acids) to displace. In that case it's just a matter of using a solution with a low pH to help get rid of bound cations.

 

[Exo]

This sounded funny to me so I went ahead and skimmed the pertinent parts of the article... I can't seem to find where the author suggests using conductive water to aid in leaching. In fact, the paragraph that I read suggested (the more-logical) opposite. The author writes:



This merely indicates that the perlite is leaching ions. In general, if you want to remove salts, you want to use as "pure" water as you can (simply to facilitate diffusion). The only reason to use a solution of water that is highly conductive would be for ion exchange. And then you'd need to worry about whatever ion you're exchanging for...

So unless I'm missing something, I think that you may have misinterpreted the author.

AWWW CRAP!!!!! I thought he meant that HE INCREASED the conductivity over a couple of days!

 

[Est]

AWWW CRAP!!!!! I thought he meant that HE INCREASED the conductivity over a couple of days!

Science to the rescue! I think you've got it now, but in case there's any confusion: The rise in conductivity was due to the leaching of ions out of the perlite and in to the water. There's no convenient way for Average Joe to measure ion presence directly, so we use conductivity because we know the correlation between conductivity and ion presence (we can actually make quantitative statements about ion concentration based on conductivity).

On that note, however, I'm somewhat disappointed that the author didn't include a control for this part of the experiment. He mentions that the article is not a traditional study, but this would've been a VERY easy control setup. We don't know much about his RO setup, so I'd imagine that it's possible that there could be normal pH fluctuation for a while after purification... I don't know to what degree, off hand, though. Anyone with more experience with RO have a quantitative range?