Cleaning the Environment with Iron Nanoparticles

Roland Piquepaille writes "In "Nanoscale Iron Could Help Cleanse the Environment," the National Science Foundation (NSF) reports that "nanoscale" powder made from iron could be used to clean contaminated soil and water. "Iron's cleansing power stems from the simple fact that it rusts. When metallic iron oxidizes in the presence of contaminants, these organic molecules get caught up in the reactions and broken down into simple carbon compounds that are far less toxic." Using this technology, cleaning landfills or industrial sites would cost about $5 per square meter. More details are available in this summary, including other links and a diagram showing how the method works."

Comments

Why doesn't this already occur?

[El]

Isn't there already lots of iron at these sites? Is the problem that we're not grinding it up finely first?

Re:Why doesn't this already occur?

[Drakin]

Surface area. Chunks of iron have less surface area than this nanoscale stuff. The story does mention that many companies already use a coarser form of this to help purify the wastes.

Re:Why doesn't this already occur?

[fireduck]

the size is part of the issue (smaller particles have more surface area). the more important point is that iron in the evironment is already in an oxidized state, e.g., Fe(OH)2. And it is the oxidation/reduction reaction that is driving the detoxification of the compounds. Specifically, Fe0 goes to Fe2+ or Fe3+, giving up 2 electrons which then are used to reduce the compound. (reduction also has the benefit that it usually makes the compound more amenable for microorganisms to chew up naturally).

This site has some diagrams of chemical pathways. Also try googling "zero valent iron".

Downside

[mchappee]

There's no mention in the article of a downside. These things *always* have a downside. Anyone know what it is?

Matthew

Re:Downside

[eugene ts wong]

There's no mention in the article of a downside. These things *always* have a downside. Anyone know what it is?

That's a good question. I don't know the answer, but maybe the catch is in finding a good way to grind up enough iron. I figure that it would take a whole lot of it to cover up the mistakes that people have made. Iron is a natural resource like trees. Trees take a long time to grow back. If we aren't careful with our iron management, then how will we gather up all this rust for new products?

Re:Downside

[Anonymous Coward]

Ok, I've got one, but not the kind you expect.

I bet this stuff is a fire hazard. Our teacher once blew air across iron filings and lit the cloud with a flame. Impressive. Surface area makes a big difference. He said he's seen someone pour iron filings from a height and the friction with the air ignited the cloud. He said. I don't know if it's true, but I'm pretty sure that nanoparticles would be very dangerous if you mixed them with air.

Just read the article. :-) Sounds like they plan to use it in a slury. Still, there could be dust after things dry. Maybe?

Re:Downside

[aXis100]

Iron is one of the most common elements on the planet. There are *enourmous* resources of it - especially in north west Australia.

The downside is, it takes energy to process and AFAIK results in in pollutants.

Re:Downside

[Ugodown]

Everything is turned into a rust colour?

Re:Downside

[marcovje]

Iron is quite natural, however treatment with iron could make the soil slightly acidic.

That and maybe the amount of base chemicals to create the dispersion and a possible neutralisation
afterwards are the only things I can think of.

Re:Downside

[Anonymous Coward]

Yes, there is a very big downside associated with basically any metal that's been ground to the nano scale. When the dust happens to fluff up into the air a little bit, the same exact thing that happens at flour mills will happen: EXPLOSIONS. Sure you don't reduce the activation energy for one Iron atom by grinding the stuff, but when you all of a sudden have lots of iron surface area (i.e. iron that can react at any given time) all you need is a spark and the right concentration and the heat from the oxidations will be enough to perpetuate the reaction, and you wind up with a pretty nice boom.

While this is a step in the right direction...

[Anonymous Coward]

While this is a step in the right direction, shouldn't we excersize more caution when dealing with products of nature? I just heard that rust was, you know, kinda poisonous. I'm not saying man should question the ineffable will of Mother Nature, just that we should think carefully about this.

Re:While this is a step in the right direction...

[El]

Iron oxide occurs naturally. People have been cooking with iron frying pans for years, and studies show it's actually good for you in trace amounts. Eating an entire frying pan in one sitting, however, is most likely bad for you.

Re:While this is a step in the right direction...

[Anonymous Coward]

Not really. Rust isn't poisonous. It's only slightly harmful, and then, only in large amounts. In fact, rust byproducts are actually used pharmacetically. Besides, at any rate, it's still going to be better than the stuff that's already there.

Re:While this is a step in the right direction...

[shamino0]

studies show it's actually good for you in trace amounts

I should hope so. It's the key ingredient in hemoglobin, without which, most human and animal life on Earth could not exist.

Eating an entire frying pan in one sitting, however, is most likely bad for you

For more reasons than just the iron content. :-)

Re:While this is a step in the right direction...

[MainframeKiller]

Eating an entire frying pan in one sitting, however, is most likely bad for you.

So if you eat it standing up, you're okay? ;-)

Re:While this is a step in the right direction...

[aXis100]

It's the key ingredient in hemoglobin, without which, most human and animal life on Earth could not exist.

Strangely enough, Ive heard that most men have too much iron since they dont bleed very often and tend to eat more red meat. Aparantly men can benefit from regular blood donation to lower their levels.

Women on the other hand tend to bleed regularly (if you know what I mean) and eat less meat. They are generally are low on iron levels. So, give that frying pan to your wife/girlfriend to chew on.

Re:While this is a step in the right direction...

[Alsee]

Eating an entire frying pan in one sitting, however, is most likely bad for you.

Remember to always save half for lunch!

-

Re:While this is a step in the right direction...

[WhiteDragon]

so what you are saying is that we should go back to using leeches for health! :-)

Re:While this is a step in the right direction...

[Anonymous Coward]

Well, the problem is really that men aren't fighting and hunting enough these days. We're probably evolved to withstand significant and repeated blood loss in combat with each other and other animals.

Re:While this is a step in the right direction...

[drinkypoo]

Put a good strong magnet in a bag of iron-fortified cereal sometime, and you will pull out iron dust, essentially very tiny filings of the stuff. I don't eat cereal, but I do cook on cast iron, so it's all good.

$5 per m^2

[pbox]

That comes out to $INF per m^3. Too bad...

What kind of whacky measurement is this? Waste is (last time I checked) three (!!!) dimensional.

Re:$5 per m^2

[Feztaa]

I didn't RTFA, but I would assume that when somebody refers to a land area in m^2, they're probably trying to say "of average depth".

As in, "for the average depth of garbage at your average landfill, it will cost $5 per m^2, all the way down to the bottom"

Re:$5 per m^2

[pbox]

You are probably right, however I do, regretfully, recall that the dump inext to the highway in north Palm Beach County, FL, where the average depth of the landfill was about 200-300 yards. I however seriously doubt that iron spread on top of that landfill would reach to bottom of it in the sunnier side of a thousand years. Maybe they meant to say for each layer (that should be about 2-3 yards). So it is still cheap if $5 takes care of 2-3 m^3...

Re:$5 per m^2

[barakn]

They use injection wells. The nanoparticles then get carried from the injection site by groundwater. The method relies on the fact that the contaminants are generally soluble in water, and so the nanoparticles should get carried to wherever the contaminants are. They suggest one well and 11.2 kilograms of iron will treat 100 m^2. But they need to use a lot more iron then to just reduce the contaminants, as the soil naturally has plenty of reducible compounds. Presumably there is more or less a constant amount of these materials per square area of soil (for instance, most organic compunds are confined to the uppermost layer). In fact, in order to drive the contaminant reduction to completion, one should probably use even more than enough iron to reduce all the reducible compounds, natural and contaminant. That's how one could come up with a constant cost per square area.

Having said that, I'm sure the actual dose does vary depending on the hydrology, geology, biology, and type and scope of contamination. The importance of the 5$/m^2 figure is to compare it with the price before they reduced the cost of making the iron nanoparticle, which was about 50$/m^2. Reducing the cost by an order of magnitude is very significant.

Nanoscale titania works too.

[auferstehung]

Nanoscale titania (esp. anatase) is also useful for pollution cleanup. Some researchers are even combining it with nanoscale iron oxed.

See this Google search and this page

Rust commentary

[annisette]

I am not supprised, as Neil Young sings, Rust never sleeps.

Iron can be toxic

[kelleher]

Iron Poisoning is one of the most frequent causes of poisoning death in children.

Re:Iron can be toxic

[shamino0]

Iron Poisoning is one of the most frequent causes of poisoning death in children.

That article is talking about children overdosing on iron pills. You'd have to eat a lot of dirt to get that kind of iron into your system from the ground.

Re:Iron can be toxic

[dnahelix]

...and what if it gets into the water and a lake full of fish ingest all that iron? I think the point is valid and the original post should NOT be modded Troll. That is too harsh. The link that is provided does go into detail about how iron can be poisonous.

"What happens in an iron overdose?
When someone takes too much iron, the first effect is irritation and ulceration of the stomach lining. This results in nausea, abdominal pain and vomiting as early as 20 minutes after the ingestion. This can be followed by an apparent recovery, which is very deceptive because a few hours later the person can go into pro-found shock with a severe blood chemistry imbalance. When too much iron gets into the bloodstream, it goes to all the organs and can damage the stomach, liver, kidneys, lungs, blood vessels and brain. "

The completely valid question is could this happen to animals if a lot of nanoscale particles of iron were released into the ecosystem?

Re:Iron can be toxic

[fireduck]

...and what if it gets into the water and a lake full of fish ingest all that iron?

this will likely not happen. as someone who studies the transport of nano-sized particles in porous media, i can tell you the iron isn't going to migrate too far. (i research virus / bacteria filtration in subsurface environments.)

the particles begin with a 0 net charge on them. however, they are quickly going to oxidize, likely to Fe(OH)2. This compound is itself ionizable depending on the solution pH (too early for me to get my chem book out). It'll become positive. Consider the bulk sediment phase (i.e., the subsurface rocks and minerals) are generally negatively charged. You've now got positively charged nanoparticles flowing through a negatively charged matrix. Very quickly you're going to have physicochemical filtration and remove the particles from the bulk solution (in my experiments, i can remove 99% of the negatively charged particles i inject into a positively charged column with 3 cm!). So they'll be immobilized somewhere in the groundwater and unable to get to the hypothetical lake.

Re:Iron can be toxic

[Cyno01]

This is certainly true of the chewable children's vitamins with iron that are often in cartoon shapes with various colors and fruit flavors.

More specifically than just iron poisoning, Flintstones Chewable Vitamins are one of, if not the most common, causes of poisining in children.

Re:Iron can be toxic

[Anonymous Coward]

Anything is toxic in sufficient quantities.

Like aluminum. There's some aluminum in Total (the breakfast cereal). But if I wack you with an aluminum bat it will be detrimental to your health.

Marsaforming Earth?

[HTH NE1]

Great, just do that to the whole Earth and it will be just as clean as is Mars today!

Will not work.

[DigiShaman]

If you spray water into a fine mist in sub-zero climate, then you will get instant snow. But if you spray an ultra fine powder of iron in a humid inviroment, chances are great that it will be rust by the time it lands on the ground. In fact, all you have to do is look at your own blood. It turns red the moment the hemogobin reacts with oxygen...which is made up if trace amounts of iron.

Re:Will not work.

[bitMonster]

LTFD (Look at The F* Diagram). They are injecting it into the ground using special wells.

A simple chemical downside.

[Bahumat]

Rusting iron consumes free oxygen. When used in water sources, this can be a very Bad Thing for most closed-system watersheds.

Powdered iron has been suggested as a means of controlling greenhouse buildup by scattering hundreds of tons of it across the surface of the pacific ocean; it creates dramatic blooms of algae in the water that suck up carbon dioxide and other pollutants.

The problem to this, of course, is that the ocean is a closed-system as well, albeit a far larger one. The iron rusts, consumes oxygen, leaving fish in oxygen-deprived waters and with little place else to go. (Fish aren't immune to pressure, quite the opposite, so no, going down isn't much of an option.)

Is anyone else thinking thermite?

[Anonymous Coward]

OK, so all we gotta do is take our nanoscale iron, let it rust into nanoscale rust.

Mix in a percentage of nanoscale aluminium.

Light a nanoscale match and WHOA!!! The quickest burning 7000 degree thermite I can think of.

mmmmm..... thermite.....

Re:Is anyone else thinking thermite?

[iggymanz]

don't forget the magnesium; otherwise you're only going to get 2200 degrees

High risk of heat and hydrogen

[G4from128k]

I noticed a product called ThermaCare that uses an air-iron exothermic reaction to create a single-use heating pad. The description of the ingredients at ThermaCare's FAQ suggests some interesting and bad consequences of iron oxidation reactions. These include:
- the potential for generating uncontrolled levels of heat depending on the mix of iron, air, and accelerants.
- the potential for generating explosive hydrogen gas (in forming iron oxide from iron and water, hydrogen is left over).

Nanoscale iron reactions may well detoxify many pollutants. But high heat generation could volatilize solvents and explosions in and around contaminated soil don't seem wise either. I assume that some test samples would ensure that the soil was not too aerobic so that heat and hydrogen generation would be sufficiently gradual to forestall a dangerous reaction, but testing will always be imperfect.

Re:High risk of heat and hydrogen

[iggymanz]

yeah, powdered iron is very flammable and can even be explosive if suspended in air - yikes!