Researchers figure out how to extract green iron from mining waste

After the extraction, the remaining waste is less harmful to the environment.

See full article...

 

[wagnerrp]

This isn't an electrochemical process, it's a chemical reduction using hydrogen. The hydrogen was apparently generated using electrolysis. Not very energy efficient, but the electrode degradation problems you are quoting don't apply.

From the article...

They heated some of the material in an electric arc furnace

These are the electrodes.

Though it doesn't really matter. The electrodes are an intentionally sacrificial component. You don't have to "worry" about electrode degradation, because you've already accepted it as an inevitability, and are using relatively inexpensive graphite rods.

 

[ajg]

This isn't an electrochemical process, it's a chemical reduction using hydrogen. The hydrogen was apparently generated using electrolysis. Not very energy efficient, but the electrode degradation problems you are quoting don't apply.

Yes, I was wrong about that comment, I apologize for that. I misunderstood the article the first time I read it, and thought it was an attempt at electrolyzing iron out of the red mud (which I thought about and looked up some years ago). This process thus falls under the bigger group of chemical processes which have been proposed to deal with red mud.

So this is more promising than I originally thought, though I would still be cautious about it. There have been a large number of experiments and proposals to use red mud over the years, and there is a high chance this has been tried before and was problematic in some area, or that it still could have unforeseen problems, like every other proposal. But at least it has a chance to work, where all previous approaches have failed.

I expect the energy consumption to primarily come from electrolysis production of hydrogen if the process is fully commercialized, since the electric arc heating is mostly done to maintain a temperature. Unless the process is highly endothermic (it consumes all the heat and leaves the products cool at the end), most of the heat will not be consumed, but vented outside as the products and remaining red mud cool off after the reaction. That heat is better recycled to heat the next batch of red mud. So in a commercialized version, the products of the reaction (presumably still hot) would be cooled by air or water, and the resulting hot air or water is used to preheat the next batch of red mud going into the reaction. Electric arc heating would only be used to replace the heat that was lost due to inefficiency in the process, which should be a small fraction of the energy used in the process. So that leaves electrolysis to produce hydrogen as the main energy cost in this reaction.

 

[chrontius]

This idea has been tried for decades though, and it still has problems with electrode contamination and degradation.

For most research into red mud, there are papers like these that largely focus on chemical or other methods of processing red mud into something more useful and less toxic:
Value added metal extraction from red mud
Extraction of Valuable Elements from Red Mud with a Focus on Using Liquid Media—A Review
Red Mud: A Resource or a Waste?
A Review on Comprehensive Utilization of Red Mud and Prospect Analysis
And if you google things like "red mud electrolysis iron," "red mud electrolysis iron recovery," "red mud recovery," or something like that, there are a vast number of research articles stretching back decades, most focused on chemical processes. But there are a few articles that focused on electrolysis, and they generally report (at least when I looked this up on a whim a few years ago) that the process was impractical:

Production of electrolytic iron from red mud in alkaline media
This one from 2020 mentions at the beginning that "The moderate performance of the process
investigated with red mud was attributed to a troublesome adsorption of red mud particles on the
cathode, making the reduction far less efficient than that with hematite."

Extracting value from aluminum production waste (red mud)
This experiment tried electrowinning, and towards the end of the powerpoint mentions "The low yield obtained in the case of bauxite residue can be explained by the presence of impurities in the medium (vanadium, silicates,..)." The efficiency was only 20% with red mud compared to 93% with hematite- at the end it recommended that a way be found to eliminate or reduce the effects of impurities.

AN INVESTIGATION INTO THE PYROMETALLURGICAL AND ELECTROMETALLURGICAL EXTRACTION OF IRON FROM “RED MUD” GENERATED IN THE PROCESSING OF BAUXITE ORES
This one from 2002 is the most detailed on electrolysis of red mud, but concludes that "The electrowinning scheme was found to be conditionally successful, but required strict process control, while the electrorefining scheme met with problems associated with anodic dissolution."

As far as I know, every previous experiment with electrolyzing red mud has had problems with the electrodes collecting a bunch of impurities that either block them from working, or dissolve/wear them away entirely. The studies usually conclude that the technology requires further development and is not yet practical for this reason. That's why this idea is still experimental, otherwise it would have been put into mass use decades ago.

Wait vanadium and silicates? That's starting to sound like some high-dollar corrosion-resistant high-speed-steel alloys right there. Maybe just start using raw red mud from characterized sources as an alloying component and skip all the refining steps…

the products of the reaction (presumably still hot) would be cooled by air or water, and the resulting hot air or water is used to preheat the next batch of red mud going into the reaction

Or the products themselves be run directly through a countercurrent heat exchanger with no intermediate, if the product is in the form of a dry powder that can be poured or moved via screw conveyor.

 

[Zizy]

my dismissiveness is that idea that 1) efficiency will save us. It won't. 2) we've been so focused on efficiency, we haven't tackled the truly hard questions. Like how do we eliminate all coal (or natural gas, or oil burning) powered foundries? I'd rather have the $XXm we spent changing lightbulbs re-building a major furnace into being electric arc powered. Or expanding the interconnects so that enough power for an electric arc furnace could flow from a green energy source.

Cheap or excess power has never been the problem. as someone else put it here, the PROBLEM is that we've been subsidizing cheap & excess power by masking (or ignoring) it's pollution effects. Why are we fighting about home HVAC efficiency when we should be replacing every major manufacturing tool with an electrical powered one. And making green electricity so damn cheap that it beats coal.

Let me give you a good example. I have a few apartment complexes in Chicago / Minneapolis area. Brand new buildings, LEED, super efficient. Yet we still lose tenants because their electric bills to heat are too high relative to them having a natural gas powered furnace. If green electricity was cheaper, it wouldn't matter that we use MORE energy to heat the space than gas. It would be the BETTER choice. Let's put fossil fuels out of business by making them the bad business choice.

Because there are problems that you can solve fine on a local scale and there are problems you cannot. Prohibiting inefficient end consumer junk is trivial - if other countries keep using that, well, their own problem. Prohibiting non-CO2-neutral steel is next to impossible. See the Russian oil... and that's for sanctions against a country where EU and USA agree and they only needed to source other oil.
Yeah, you can heavily tax coal or gas locally... but all you did is destroy industry relying on it.

Second point is that you can do more than just one thing; and we do. You know what is happening for consumers because that involves you. You probably have no idea what is going on in various pilot projects to decarbonize industry.

Besides, lightbulbs were fairly cheap to gradually replace and those costs were distributed among everyone easily. It isn't like we forced people to accept something much worse in the name of efficiency. Yeah, short term situation sucked, but now we have much better and cheaper lighting than we used to.

As for your apartments, what is "super efficient"? My few years old house has 20cm insulation and is (supposedly) 25 kWh/m2/year. That was/is pretty normal though increasingly many houses have better insulation, reaching "passive" grade. Total electricity costs (heating, warm water, cooking and the rest) per year are about 1k eur. Gas would cost the same if not more.

 

[whobeme]

That's what happens when you buy cheap single-stage heat pumps for your Minnesota tenants, and then experience a week of sub-zero lows.

According to the plot here:

https://www.engineeringtoolbox.com/heat-pump-efficiency-ratings-d_1117.html
the COP at -20C (-4F) outside and 20C inside is about 7. Factor in a real world system which is not very close to the theoretical limit, and possibly a building which is not perfectly insulated, and a cold snap could result in a very large amount of electrical use. Not sure what the rate structure in that state is, but here in CA it is tiered, so using 2X the electricity in a month can be much more than 2X as expensive. Same problem (in reverse) for very hot months, where the A/C efficiency decreases. Anyway, I can believe that the electricity bills could exceed the natural gas bills in very cold months in many buildings for the same internal temperature settings even with the best heat pump on the market.

Doesn't mean that heat pumps are bad, it might very well mean that the building insulation needs work.

 

[JMTronicHobbyist]

This idea has been tried for decades though, and it still has problems with electrode contamination and degradation.

For most research into red mud, there are papers like these that largely focus on chemical or other methods of processing red mud into something more useful and less toxic:
Value added metal extraction from red mud
Extraction of Valuable Elements from Red Mud with a Focus on Using Liquid Media—A Review
Red Mud: A Resource or a Waste?
A Review on Comprehensive Utilization of Red Mud and Prospect Analysis
And if you google things like "red mud electrolysis iron," "red mud electrolysis iron recovery," "red mud recovery," or something like that, there are a vast number of research articles stretching back decades, most focused on chemical processes. But there are a few articles that focused on electrolysis, and they generally report (at least when I looked this up on a whim a few years ago) that the process was impractical:

Production of electrolytic iron from red mud in alkaline media
This one from 2020 mentions at the beginning that "The moderate performance of the process
investigated with red mud was attributed to a troublesome adsorption of red mud particles on the
cathode, making the reduction far less efficient than that with hematite."

Extracting value from aluminum production waste (red mud)
This experiment tried electrowinning, and towards the end of the powerpoint mentions "The low yield obtained in the case of bauxite residue can be explained by the presence of impurities in the medium (vanadium, silicates,..)." The efficiency was only 20% with red mud compared to 93% with hematite- at the end it recommended that a way be found to eliminate or reduce the effects of impurities.

AN INVESTIGATION INTO THE PYROMETALLURGICAL AND ELECTROMETALLURGICAL EXTRACTION OF IRON FROM “RED MUD” GENERATED IN THE PROCESSING OF BAUXITE ORES
This one from 2002 is the most detailed on electrolysis of red mud, but concludes that "The electrowinning scheme was found to be conditionally successful, but required strict process control, while the electrorefining scheme met with problems associated with anodic dissolution."

As far as I know, every previous experiment with electrolyzing red mud has had problems with the electrodes collecting a bunch of impurities that either block them from working, or dissolve/wear them away entirely. The studies usually conclude that the technology requires further development and is not yet practical for this reason. That's why this idea is still experimental, otherwise it would have been put into mass use decades ago.

My reading isn't that they used electrolysis but heat. The arc furnace heats it and the hot hydrogen is doing the rest of the work. I suppose there will be some gasses boiling off which might attack the electrodes though.

 

[purposelycryptic]

It's crazy to me that we allow mining of other industrial processes to occur that leave toxic waste in pools like this... forever.

As far as I understand, the pools don't get less toxic over time, they just... sit there. Invariably, at some point all of these pools will decay/fail and be released into the environment, and in the meantime they're expensive to maintain and present an ongoing hazard to any wildlife that happens to be nearby.

A pool like this only makes sense if the environmental risk of its contents naturally decreases, decays, or breaks down over time, or if it's a temporary holding point before further reprocessing. Otherwise, anybody whose mining plan results in production of an indefinite environmental hazard like this simply shouldn't get a permit unless they have some way to remediate it to a stable state.

Presumably solutions exist, like the one described in the article, or something like vitrifying the waste to dramatically reduce its reactive surface area to safe levels then burying it back where it came from. I'm guessing these are considered too energy intensive or expensive (same thing) but tough luck. That just means you're stealing productivity from the future by making it somebody else's problem down the road.

If we really refuse to require proper abatement for forever waste like this, then we should honestly prohibit pools like this from being created and just release the waste directly now. At least that way we're not wasting money maintaining a pointless pool to delay the problem "for a while" while solving nothing, and it means that current generations get to deal with the environmental effects of their actions now, rather than foisting them off on future generations that don't get a say in the matter.

These pools seem like an excellent location to relocate the more idiotic parts of our populace to - we just need to add some white and blue toxic waste pits, and they would probably do it voluntarily, to show off their "patriotism".

 

[kkeane]

Why not? generally with any sort of process water (not cooling water) its generally best practice and cheaper to recycle most of it so you dont need as much Reverse Osmosis or similar to resupply water with sufficient purity

Except in this case, you would need to purify the water either way; recycling the water doesn't seem to buy you any benefit.

Of course the situation would be different in a desert.

 

[mhalpern]

Except in this case, you would need to purify the water either way; recycling the water doesn't seem to buy you any benefit.

Of course the situation would be different in a desert.

sure it does, in this case the water you're recycling can be recovered as steam, this means you can get it to a pretty pure state through simple distillation, and because a lot would be as steam, the typical option if you aren't recycling it is to let the steam evaporate rather than letting it flow as water back into the source. Also aluminum production uses a lot of water and while you may get some of it back as you process the red mud, its likely to be a limiting factor. Basically even where you have a large supply of water, you only have so much and others need to use it too, so it's often better both politically and economically to make the best possible use of your supply.

 

[mhalpern]

Is your position that a process that has been found multiple times to be uneconomic in a lab can become economic in a pilot plant? That sounds like a "we're losing money, but we'll make it up in volume" argument.

I don't much care for defending someone else's post. How do you propose a pilot plant overcome the obstacles ajg pointed out?

Generally you use graphite electrodes, degradation isn't an issue because the electrodes are consumables in the process, the efficiency declines as they wear out, but that's the same with all arc furnaces actually it's a feature here as the electrodes can provide at least some of the carbon you need to make it a steel

 

[mhalpern]

This idea has been tried for decades though, and it still has problems with electrode contamination and degradation.

For most research into red mud, there are papers like these that largely focus on chemical or other methods of processing red mud into something more useful and less toxic:
Value added metal extraction from red mud
Extraction of Valuable Elements from Red Mud with a Focus on Using Liquid Media—A Review
Red Mud: A Resource or a Waste?
A Review on Comprehensive Utilization of Red Mud and Prospect Analysis
And if you google things like "red mud electrolysis iron," "red mud electrolysis iron recovery," "red mud recovery," or something like that, there are a vast number of research articles stretching back decades, most focused on chemical processes. But there are a few articles that focused on electrolysis, and they generally report (at least when I looked this up on a whim a few years ago) that the process was impractical:

Production of electrolytic iron from red mud in alkaline media
This one from 2020 mentions at the beginning that "The moderate performance of the process
investigated with red mud was attributed to a troublesome adsorption of red mud particles on the
cathode, making the reduction far less efficient than that with hematite."

Extracting value from aluminum production waste (red mud)
This experiment tried electrowinning, and towards the end of the powerpoint mentions "The low yield obtained in the case of bauxite residue can be explained by the presence of impurities in the medium (vanadium, silicates,..)." The efficiency was only 20% with red mud compared to 93% with hematite- at the end it recommended that a way be found to eliminate or reduce the effects of impurities.

AN INVESTIGATION INTO THE PYROMETALLURGICAL AND ELECTROMETALLURGICAL EXTRACTION OF IRON FROM “RED MUD” GENERATED IN THE PROCESSING OF BAUXITE ORES
This one from 2002 is the most detailed on electrolysis of red mud, but concludes that "The electrowinning scheme was found to be conditionally successful, but required strict process control, while the electrorefining scheme met with problems associated with anodic dissolution."

As far as I know, every previous experiment with electrolyzing red mud has had problems with the electrodes collecting a bunch of impurities that either block them from working, or dissolve/wear them away entirely. The studies usually conclude that the technology requires further development and is not yet practical for this reason. That's why this idea is still experimental, otherwise it would have been put into mass use decades ago.

I suspect part of the role of the hydrogen here is to reduce the work of the electrodes thereby reducing the degradation. As I understand it previous experiments didn't make use of a reduction agent.

 

[wagnerrp]

I suspect part of the role of the hydrogen here is to reduce the work of the electrodes thereby reducing the degradation. As I understand it previous experiments didn't make use of a reduction agent.

Er... you can't reduce something if you don't have a reducing agent...

 

[numerobis]

Er... you can't reduce something if you don't have a reducing agent...

Electrolysis isn’t reduction but still gets you the metal you wanted.

 

[luptonma]

A 30 per cent iron solution by weight doesn't seem like it would be particularly potent in a homeopathic sense.

I think you missed the sarcasm and the whole point of the process. Plus you don't seem to understand the premise of the widely disproven theory of homeopathy. The 30 percent iron is removed as metal. The "residual red mud," which wouldn't be very red because all but a mere trace of the iron is gone, would be used for homeopathic treatment of anemia; which is iron deficiency.

You see the deluded practitioners of homeopathy believe, based on no confirmed scientific evidence, that vanishingly small traces of biologically active agents can cure disease by creating negative templates of the agent in water molecules. These water templates are alleged to be biologically active themselves so they react with your body to cure disease, neutralize poison, eliminate wrinkles, enhance sexual performance, or any other crazy medical benefit late night TV advertisers can dream up. Presumably in the case of anemia a vanishingly small concentration of iron would create water molecule templates that look like iron, or maybe "negative iron," which would cure, anemia.

This is funny, hilarious I think, because homeopathy is a complete load of biological bullshit based on near infinite dilution of biologically active compounds. You know, sarcasm.

 

[mhalpern]

Electrolysis isn’t reduction but still gets you the metal you wanted.

Even then there are other ways, heat something up hot enough in an inert atmosphere or thin atmosphere or even vacuum and you can separate the oxygen from the ore without use of a reduction agent.

 

[you goddamn idiot.]

I think you missed the sarcasm and the whole point of the process.

No, I get it. My point was that 30% weight for weight is too high a concentration by homeopathic principles; you'd need to dilute it by several orders more. Since it was pointed out by another commenter that I misread the article and got the ratio wrong, in a later comment I went straight to the journal article and calculated that the remainder of the red mud actually still contains 17.8% iron weight for weight, which is still too high to be useful for homepathy.

 

[wagnerrp]

I think you missed the sarcasm and the whole point of the process. Plus you don't seem to understand the premise of the widely disproven theory of homeopathy. The 30 percent iron is removed as metal. The "residual red mud," which wouldn't be very red because all but a mere trace of the iron is gone, would be used for homeopathic treatment of anemia; which is iron deficiency.

This was a chemical reaction. Homeopathy doesn't condone the use of any of those hazardous, amoral sciences like chemistry.

Water was created, but was immediately extracted as steam. This was a refinement, the exact opposite of dilution. There was definitely no licensed homeopathic practitioner pounding on the crucible with the magical wooden paddle.

 

[luptonma]

Except in this case, you would need to purify the water either way; recycling the water doesn't seem to buy you any benefit.

Of course the situation would be different in a desert.

These large open pits do actually recycle the water using solar power. The sun evaporates pure water into the air leaving solid waste behind. The ponds with water in them are still being actively filled with waste fast enough to keep the level steady but eventually they silt up so much no more waste can be added. At this point they are left to dry out then the solid waste is scooped up and safely sequestered in a properly lined and capped landfill. The drying ponds are supposed to be lined so the contaminated water doesn't seep into the ground. This can work great in theory but in practice companies skimp on lining the pond, reinforcing the pond walls or they add too much waste and cause a spill that is very bad for the local ecology. Companies also go out of business before safely landfilling the waste or just never bother because it is expensive to properly manage waste and ignoring the problem is almost free.

This development might make it more profitable to process the waste than to abandon it; which would be great. The ONLY way to get companies to perform the actions you want them to, like cleaning up after themselves, is to make it more profitable for them to do the action than not do it. Shaming them publicly can generate enough negative publicity to force action in some cases but most companies, particularly large ones, are shameless and find it cheaper to spend money on public relations campaigns rather than cleaning up their messes. Regulations with hefty fines are better but enforcement is expensive, controversial and prone to corruption or even abandonment after the problem gets "solved" for a while and business interests lobby for getting rid of restrictive rules that hurt domestic competitiveness. Best is to figure out how to turn the action you want to happen into a profitable business without adding a lot of regulations that could be ignored or abandoned. in the end some regulation is inevitable if you don't want the clean up companies just pocketing the clean up money and leaving a potentially worse mess behind.

 

[luptonma]

No, I get it. My point was that 30% weight for weight is too high a concentration by homeopathic principles; you'd need to dilute it by several orders more. Since it was pointed out by another commenter that I misread the article and got the ratio wrong, in a later comment I went straight to the journal article and calculated that the remainder of the red mud actually still contains 17.8% iron weight for weight, which is still too high to be useful for homepathy.

Yeah I missed the part about 17.8% being left too. I still think the homeopathy comment was amusing though.

 

[luptonma]

Electrolysis isn’t reduction but still gets you the metal you wanted.

Electrolysis is reduction. The reducing agent is electrons. All reducing agents work by transferring electrons to the reduced atom or molecule.

Some processes reduce things "chemically" by bumping atoms against each other in a solution and letting the electrons jump to the more electrophilic bits in the solution. Others do it "electrochemically" using a voltage source, wires and electrodes to inject electrons into a solution and reduce certain things at one electrode, the cathode, while sucking electrons out and oxidizing other things at the anode.

For iron oxide, or any metal oxide, you are reducing a metal atom in a metal by adding electrons to it so it doesn't have to share electrons with oxygen. The metal atom is then free to form a metallic bond with the cathode metal and plate out as a reduced metal instead of floating around in solution as a metal ion. When you reduce with hydrogen gas you use heat to form H radicals and slam them into metal oxides where the H radicals glom onto oxygen atoms eventually forming water and flying away as steam. The lone metal atom is left with only an electron or two to remind it of the intimacy it once shared with oxygen. These lonely neutral metal atoms drift aimlessly until they find other lone metal atoms that they can share their electron memories with. Eventually the metal atoms all congregate in a metal bar where they commiserate over a few beers until a some carbon atoms come along and steel the show. When an attractive oxygen atom passes by the metal bar some metal atoms leave and are corroded back into oxides. They never learn.

 

[Wickwick]

Electrolysis is reduction. The reducing agent is electrons. All reducing agents work by transferring electrons to the reduced atom or molecule.

Some processes reduce things "chemically" by bumping atoms against each other in a solution and letting the electrons jump to the more electrophilic bits in the solution. Others do it "electrochemically" using a voltage source, wires and electrodes to inject electrons into a solution and reduce certain things at one electrode, the cathode, while sucking electrons out and oxidizing other things at the anode.

For iron oxide, or any metal oxide, you are reducing a metal atom in a metal by adding electrons to it so it doesn't have to share electrons with oxygen. The metal atom is then free to form a metallic bond with the cathode metal and plate out as a reduced metal instead of floating around in solution as a metal ion. When you reduce with hydrogen gas you use heat to form H radicals and slam them into metal oxides where the H radical gloms onto oxygen atoms, eventually forming water and flying away as steam leaving the metal alone with only an electron or two to remind it of the intimacy it once shared with oxygen. These lonely neutral metal atoms share these electron memories with other lonely metal atoms as they congregate at the metal bar where they commiserate over a few beers.

I believe the term "reducing" is referring to the electron state of the atom in question. So reduction can happen from radiation, electrochemistry, or just chemistry.

 

[mhalpern]

I believe the term "reducing" is referring to the electron state of the atom in question. So reduction can happen from radiation, electrochemistry, or just chemistry.

and a reduction agent is a chemical that reduces or aids in reduction

 

[kkeane]

sure it does, in this case the water you're recycling can be recovered as steam, this means you can get it to a pretty pure state through simple distillation, and because a lot would be as steam, the typical option if you aren't recycling it is to let the steam evaporate rather than letting it flow as water back into the source. Also aluminum production uses a lot of water and while you may get some of it back as you process the red mud, its likely to be a limiting factor. Basically even where you have a large supply of water, you only have so much and others need to use it too, so it's often better both politically and economically to make the best possible use of your supply.

Thanks for clarifying it. Now it does make more sense!

 

[Wickwick]

and a reduction agent is a chemical that reduces or aids in reduction

Yes, as in "reagent." Ergo, electricity isn't a reducing agent even if one is reducing a molten ore body through electric discharge.

 

[mhalpern]

Thanks for clarifying it. Now it does make more sense!

same sort of reason why most steam power plants have a closed cycle on the working fluid/steam water loop, the steam that you see coming out of the cooling towers is entirely separate water, less water to clean up before running it through the machinery, yes there's some loss so you need to replenish some water, but it's a lot less

 

[Helmore]

It's "carbon neutral" in that carbon is not fundamentally required in the process. It uses hydrogen and electricity, and that hydrogen can be produced through water and more electricity. Bonus, it's process water that can be fully recycled into fresh hydrogen. Bonus bonus, if you've got the electrolysis cell anyway, it may be worthwhile to set up hydrogen storage, as a means of load shifting, to keep the plant hot and operational.

It will be cheaper to set up battery storage and use that to do the load shifting. The capital costs for the equipment to do your own electrolysis means that you want that electrolysis cell, and the rest of the plant that comes with it, running at 100% capacity 24/7. If you are not doing so, that means you spend a lot more on this expensive equipment than was needed.
To be able to do load shifting, your electrolysis plant needs to have more capacity than you need and will be even more expensive on top of that to allow for much more expansive (and expensive) storage. A huge battery bank will most likely be cheaper and give you a lot more flexibility, as you also need electricity in your process, not just hydrogen.

EDIT: The battery bank will probably also have lower operating costs.

 

[ArcaneTourist]

Minor suggestion - In the article, change "very basic pH" to maybe "very high pH (alkaline)". This is Ars, but still I'd guess that not everyone took high school chemistry...