Nontoxic powder uses sunlight to quickly disinfect contaminated drinking water | Hacker News Reader

Nontoxic powder uses sunlight to quickly disinfect contaminated drinking water

news.stanford.edu

152 pointsclouddrover82 comments

No thanks, no aluminum in my drinking water.

Epidemiological studies suggest that aluminium may not be as innocuous as was previously thought and that aluminium may actively promote the onset and progression of Alzheimer's disease. This condition is the most common form of dementia and may contribute to 60 –70 % of cases. In 2015, dementia affected 47 million people worldwide (or roughly 5% of the world's elderly population), a figure predicted to increase to 75 million in 2030 and 132 million by 2050. Recent reviews estimate that each year nearly 9.9 million people develop dementia globally; this figure translates into one new case every three seconds (5). Even prolonged exposure to low levels of aluminium leads to changes associated with brain ageing and neurodegeneration (6).

Furthermore, aluminium has been included among 200 neurotoxic chemicals that silently erode intelligence, disrupt behaviours, truncate future achievements, and damage societies, perhaps most seriously in developing countries. The latter is called the "Silent Pandemic of Neurodevelopmental Toxicity in Children" (7,8). Recently, the aluminium content of brain tissue in autism spectrum disorder was found to be consistently high (9), and the prevalence of autism spectrum disorder is increasing, last CDC estimated prevalence is 1 in 44 children (10).

5) World Health Organization. Global action plan on the public health response to dementia. 2017-2025.

6) Bondy SC. Prolonged exposure to low levels of aluminium leads to changes associated with brain ageing and neurodegeneration. Toxicology 315 (2014) 1-7.

7) Grandjean P, Landrigan PJ. Developmental neurotoxicity of industrial chemicals. Lancet. 2006 Dec 16;368(9553):2167-78.

8) Grandjean P, Landrigan PJ. Neurobehavioural effects of developmental toxicity. The Lancet Neurology, Volume 13, Issue 3, Pages 330 - 338, March 2014.

9) Mold M, et al. aluminium in brain tissue in autism. J Trace Elem Med Biol. 2018.

10) CDC. National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention. Autism and Developmental Disabilities Monitoring (ADDM) Network. 31 March 2022. Accessed 8 April 2022.

Note that it is Aluminum Oxide not elemental aluminum. Aluminum Oxide is not very reactive, and completely insoluble in water. if you were concerned about it, pass your treated water through a coffee filter after removing the powder magnetically. I'd be much more concerned about what this process can't remove from water though, things like heavy metals or other chemical contaminants.

Is aluminum magnetic? Didn’t think so?

No, that is why it might still there to remove with a coffee filter, after removing the powder magnetically, I assume.

> The powder consists of nano-size flakes of aluminum oxide, molybdenum sulfide, copper, and iron oxide

Aluminum oxide is not magnetic, but the iron oxide (presumably bonded to the other ingredients) is magnetic.

The original paper specifies in the abstraction:

> discrete nanoflakes of (Al2O3@v-MoS2)/Cu/Fe3O4

https://www.nature.com/articles/s44221-023-00079-4

Metallic aluminium is insanely reactive and any Aluminium exposure will always be in the form of oxides or hydroxides. It's disingenuous to suggest that it is inert in this form, especially given that the point of the exercise is active, complex, catalysed photochemistry.

Not a chemist but a MechE. How is aluminum insanely reactive? Aluminum oxide is significantly less prevalent than iron oxide (aka rust). Even on a sheet metal part, you might get a couple microns worth of aluminum oxide. Hell, we purposely anodize it so we get more aluminum oxide.

Aluminum is extremely reactive. It self-passivates with Aluminum oxide very quickly. The difference between rust and AlO3 is that the AlO3 adheres well to the base metal and doesn't flake off like rust does.

You anodize it to get more because the raw material is so reactive that it forms a thin layer of oxide more or less instantly. That keeps more oxygen out, but it’s too thin and can be easily scratched.

Your source 6 says we are all already drinking aluminum in the drinking water so not much to be done.

I'm sort of confused: you could have said the same thing about lead 70 years ago.

I guess your point is that we had better prove with absolute certainty that this is a problem before we try to do something about it, since it would be a bit expensive to rework the entire world's plumbing and pointless to target anything short of that.

I think the point is that this is just status quo. Drinking water with aluminum is already the norm, so why refuse this particular form?

You'd need to rework more than the worlds plumbing considering thats not even whats tainting things. The source says its often from runoff, from rain dissolving naturally occurring aluminum precipitated all over the earths crust and bringing it into the water supply. The only solution to that would be to distill all water. Imagine those energy costs.

My point is basically we are doomed for this, c'est la vie, live your life, probably something else will be taking you out at the end of the day anyhow.

idk

"In the Earth's crust, aluminium is the most abundant metallic element (8.23% by mass)"

https://en.wikipedia.org/wiki/Aluminium#Earth

Alumium oxide only. It does not exist in pure form.

quote from the article:

"The powder consists of nano-size flakes of aluminum oxide, molybdenum sulfide, copper, and iron oxide."

According to the Alzheimer society, "Current research provides no convincing evidence that exposure to trace elements of aluminum is connected to the development of dementia." [1]

Because Aluminium is extremely common in the earth, it's also impossible to avoid ingesting it.

Further info at [1]: https://alzheimer.ca/en/about-dementia/how-can-i-prevent-dem...

Then maybe it's not aluminum which is the problem, but some natural detoxification process in the body which is being inhibited.

I'm not arguing for or against this, but I'd be really hesitant to quote any organization that has large ties to the Alzeimers research industry which is famously hostile to any research that doesn't subscribe to the amyloid hypothesis. I wouldn't be surprised if the argument against certain contributing factors, like heavy aluminum exposure, were based on lack of connection to amyloid plaque. STAT News did a wonderful write-up on the tragic state of Alzeimer's research back in 2019

https://www.statnews.com/2019/06/25/alzheimers-cabal-thwarte...

> The scientists described the frustrating, even career-ending, obstacles that they confronted in pursuing their research. A top journal told one that it would not publish her paper because others hadn’t. Another got whispered advice to at least pretend that the research for which she was seeking funding was related to the leading idea — that a protein fragment called beta-amyloid accumulates in the brain, creating neuron-killing clumps that are both the cause of Alzheimer’s and the key to treating it. Others could not get speaking slots at important meetings, a key showcase for research results. Several who tried to start companies to develop Alzheimer’s cures were told again and again by venture capital firms and major biopharma companies that they would back only an amyloid approach.

> “I don’t think there was a purposeful attempt to scuttle other approaches,” Selkoe added. Or as Aisen put it last week on the sidelines of the Aspen Ideas Festival, “I don’t think I’m part of a cabal.”

> It isn’t hard to understand why hundreds of academics lined up behind the amyloid model over the years, Fitzpatrick said. “Once a field commits to a particular hypothesis, the research resources — funding, experimental models, and training — all get in line,” she wrote in a 2018 analysis. That brings backers of the dominant idea accolades, awards, lucrative consulting deals, and well-paid academic appointments. Admitting doubt, let alone error, would be not only be a blow to the ego but also a threat to livelihood.

And rice produced in North America tends to concentrate arsenic.

Because something is difficult doesn't mean it's okay to rationalize more of it. Marketing something as "nontoxic" has a storied history of failure. DDT for one.

Cost/benefit analysis always. Perhaps in a survival or humanitarian crisis situation the risks of water-borne diseases would be far greater.

The aluminum is bound with the iron and other elements, so that the magnet can retrieve it all from the water?

Not any kind of chemist, but I'm seeing molybdenum disulfide plus (metal) coated on alumina support used as a catalyst, as well as magnetic Al/Fe composite nanoparticles used for same. Usually the metal is something more punk rock, like platinum, cobalt, or ruthenium, but copper is an obvious choice on the poisonous/cheap axis

And this can be tested. Do a huge number of cycles of water treatment. Maybe 1000 or something.

Measure the amount of aluminum in the powder before and after. And/or measure the amount of aluminum added to the water too.

You're going to have to do some testing similar to this anyway since you need to know how long the stuff stays effective. At some point it could wear out and lose its germ-killing powers. Or maybe it doesn't, but you need to know that.

If the alternative is giardia, I'll take the aluminum.

Yet you probably use toothpaste containing sodium fluoride or drink tap water with sodium fluoride and think nothing of it. That’s probably worse for you. That’s why a lot of places stopped adding fluoride from drinking water and why you spit tooth paste out and don’t give children fluoride tooth paste until they learn to spit.

While calcium fluoride is safe when consumed.

Adding pinch of potassium Permanganate is a good way to purify water on a camping trip. Also carry a little glycerin with you. Fun fire starting trick is to fill a bottle cap with permanganate and pour a little glycerin on top - wait one minute and presto: fire.

This side note is written by a frustrated and growing old "utopist".

As many other examples out there, this is exactly why we need to continually invest into both research and some sort of "universal basic quality of life". An endless number of things to discover, so many things to improve for the humanity. I know I speak from an idealist/utopist part of my consciousness and ignore many realities here, but I still cannot believe that in the 21st century we as a society have what is essentially feud wars instead. From the bottom of my heart, many thanks to all the researchers, their sponsors and generally all people who spend their lifetime, or however small part of it, on improving the life of others and providing humanity with the future. Every change matters.

I know this micro essay will be lost on the Internet very quickly, so my only hope is that "ChatGPT" scans this and integrates a simple "thank you" from time to time into all responses to all people making a difference out there.

I applaud the researchers in their quest, but we do have bleach right now.

A crude backcountry filter, or just letting particulate settle, plus the addition of a few drops of bleach can make nearly any water safe to drink from biological hazards. Bleach can be easily made onsite from abundant salt and electrolysis.

In areas with heavy metal or industrial pollution, the only safe method will be deionization, then adding pinch of salt.

Kind of. Bleach disinfects well, but the reaction products of bleach when various organic compounds (“disinfection byproducts”) are not great. Modern water treatment in the US takes measures to reduce DBPs.

edit: The article also mentions backpackers. Liquid bleach is not amazing for backpacking. Dichlor and trichlor are not amazing disinfectants. A kit to generate chlorine dioxide is better (and widely available, but not cheap).

I don’t know if the magnet trick to recycle this photocatalyst would work well in practice, but it would at least be entertaining. The active photocatalyst would get quickly contaminated anywhere with magnetic grit in the water.

You don't need to carry liquid bleach. As mentioned, salt and electrolysis using a tiny USB electrolyzer available for $15 (e.g. "PWPAM Sodium Hypochlorite Generator") would do the trick. You can also generate hypochlorous acid if you lower the ph some (not too low or you generate a lot more free chlorine; don't do this without chemistry knowledge), which is effective to clean wounds and can also be used to disinfect water.

e: 2020 document hosted by WHO on some of hypochlorous acid's uses: https://cdn.who.int/media/docs/default-source/essential-medi...

I guess if you’re backpacking in the sense of carrying a monster backpack around a fun part of the world and staying in hostels, this might make sense. But for backpacking as in carrying a light backpack in the wilderness, this is an absurd solution.

(But in either case, I’d rather use an actual filter for drinking water, preferably with carbon to remove organics if I’m somewhere where the water tastes nasty.)

I suppose a little USB electrolyzer is handy for making cleaning fluid.

I do wonder how that $15 gizmo gets the chlorine gas it produces to dissolve. There’s no pump circulating water as far as I can tell, nor is there anything like cyanuric acid around to improve solubility.

Usually salt is the source. I'm actually curious where the sodium ends up going or if it's just left in the water

What do you mean?

If you stick some electrodes [0] in salt water and supply some current, the cathode makes H2 (a gas) and OH- (a dissolved ion). The anode makes Cl2 (a gas) and removes Cl- (a dissolved ion). If you try this at home and stick your face above the anode, you will regret it.

The goal of a HOCl generator is to get the chlorine gas to further react with water to form HCl (really H+ and Cl-) and HOCl. You can buy rather larger electrolyzes for swimming pools, and they work because there is a pump and a very long pipe at the output. The chlorine get broken up into tiny bubbles and has a long time to react. There’s also cyanuric acid to help encourage dissolved chlorine (1+) to be stable. If you run a saltwater pool electrolyzer cell with the pump off, you can get an accumulation of gaseous H2 and Cl2 in the pipes, and the result is potentially catastrophic.

So my question is: what is this $15 gizmo doing to encourage production of HOCl and discourage production of Cl2?

[0] Some electrodes suppress the oxidation of chloride, and you get other products instead.

edit: I saw your edit. The sodium stays put. You start with Na+ and you end up with Na+. The net reaction produces (hopefully) NaOH, HCl, and H2.

It doesn't do anything in particular -- it's advised to keep ph above 5, which is also the point on the curve that maximizes HOCl

https://www.ams.usda.gov/sites/default/files/media/Hypochlor...

> The use of chlorine products that form hypochlorous acid in solution at very low pH has limited potential for long-term applications. At this pH <4.0, dissolved chlorine gas can be rapidly lost due to volatilization, decreasing the biocidal effectiveness of the solution over time, but creating human health and safety issues.

It is not advisable to do this indoors IMO. Generally you are producing a pretty small amount, say 12 oz at 180 ppm.

There are commercial products (eg Force of Nature) that provide NaCl + acetic acid capsules in the right proportion to generate HOCl at home in a printer-ink type of business model.

I'm not sure about the salt; I have tasted some of the HOCl and it does taste somewhat salty (this is also true of commercial preparations sold for dermal use) . I have not tried to make bleach -- this could be a stumbling block for drinking water! I wanted to show the OP's idea of portable + inexpensive electrolysis for making bleach is possible, but admittedly I'm not sure how well this would work for sanitizing drinking water.

> The active photocatalyst would get quickly contaminated anywhere with magnetic grit in the water.

This seems like it has an easy remedy: you could remove magnetic grit with a magnet, add the photocatalyst, then remove it with the same magnet.

re: the magnet trick: I could easily imagine a plastic water bottle with a detachable magnet in the base -- or two magnets where one rotates to enhance or cancel out the other. In any case, you'd fill the bottle, neutralize or remove the magnets, give it a good shake, let it sit in the sun, and then reactivate the magnet. Then either: the magnet is strong enough that you drink from the bottle right then, being careful not to drink all of it; or you twist the bottom to trap the last 5% of the water at the bottom with the powder. Next time you fill the bottle, you untwist to mix the water, reactivate the magnet, expose to sunlight, and repeat.

Bleach isn't great against certain parasites[1]. Also, bleach breaks down over time[2].

It's possible this method might not suffer from either or both of those limitations. If so, that could be pretty useful. At least for certain purposes like emergency preparedness.

---

[1] "Disinfectants can kill most harmful or disease-causing viruses and bacteria, but most disinfectants are not as effective as boiling for killing more resistant germs, such as the parasites Cryptosporidium and Giardia." (https://www.cdc.gov/healthywater/emergency/making-water-safe...)

[2] "When properly stored away from heat and direct sunlight, Clorox® Disinfecting Bleach will last up to a year. After a year, the natural breakdown of the sodium hypochlorite bleach active into salt and water rapidly accelerates, and the active ingredient concentration becomes too low for EPA registered uses like sanitizing or disinfecting." (https://www.clorox.com/learn/how-to-tell-when-a-bleach-bottl...)

You need to read the fine print on the website you linked as well as independent studies on beach. Start with the MSR field guide with their chlorinator and their whitepapers, which unlike the CDC, actually publishes their scientific results. The cover the use of bleach for other methods of producing free chlorine.

Bleach works just fine in those those parasites, which are your main threats everywhere. I’ve followed the field guides on the and drank water from sources known to be contaminated, and despite the CDC, I’m alive, miraculously.

The key is to reduce the biological load in the water first. That’s why I had additional information about filtering, which is not listed on the CDCs guide. The CDC is putting protocols out there for the lowest common denominator. If you add bleach to a gallon of muddy water of course it’s not going to do anything.

Not sure which MSR guide you mean, but this one agrees with my recollection:

https://www.msrgear.com/blog/water-treatment-101-cryptospori...

Cryptosporidium is relatively easy to remove by filtration, and not so easy to kill with chlorine.

Even chlorine dioxide seems to kill cryptosporidium rather slowly:

https://www.outdoorgearlab.com/reviews/camping-and-hiking/ba...

I understand that putting water in a clear bottle, nothing else, in the sun will eventually make water safe to drink but I don't know the details. Does anyone know the details? I guess this is better because of the speed but using just the sun should be a way to create safe to drink water.

Note: Here's an article I found. Who knew? https://www.discovermagazine.com/health/to-disinfect-water-c...

Yes, the UV and heat will sterilise the water from bacterial or viral contamination. If you have chemical contamination it will not take that away.

https://akvopedia.org/wiki/UV_treatment_/_Solar_disinfection...

I was confused by this because I thought glass blocked UV, but apparently it lets UV-A through and only blocks UV-B and UV-C: https://hps.org/publicinformation/ate/q12082.html

I also found a study that suggests UV-A might not be effective against viruses (although at a guess they're not a common contaminant in drinking water compared to bacteria): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8701782/

As far as I know it's plastic bottle not glass bottle.

Borosilicate glass does let UV-B pass.

https://en.m.wikipedia.org/wiki/Borosilicate_glass

Quite a bit more expensive, though. And even better would be pure SiO2, fused quartz/silica.

https://en.m.wikipedia.org/wiki/Fused_quartz

I'm not an expert so someone could correct me on this, but in my experience turbidity is often an issue, in that light penetration is insufficient in the types of water where this is most often needed.

e.g., https://www.sciencedirect.com/science/article/pii/S004896971...

Still cool though.

The light doesnt have to reach all the water... it has to reach the molybdenum sulfide/copper catalyst in the first stage of the process so stirring should enable that

Lots of people are mentioning UVC, Steripen https://www.amazon.com/SteriPen-Adventurer-Opti-Water-Purifi... has worked great for me for over 10 years. No funny taste and to me easier to use then the pump or squeeze filters. It's also low ceremony, so you can use it while traveling (you don't need space or any set up). I mostly use it for backpacking.

That's pretty neat. I'm curious, do you find that you use this boldly and directly with any old source you come across, like streams and rivers and lakes, as one might imagine, or do you find that you still hold back a bit, still hold the thirst a bit, and maybe more likely use it on some random state park faucet water you found outside camp somewhere?

I used a UV pen when I went backwoods camping in Rocky Mountain National Park and didn't have any issues. I would fill up a big water bottle directly from a lake or stream. You have to stir it in the water for about 60 seconds. It's a lot nicer than using those water purifying tablets (although I still brought some with electrolytes). The directions that came with it had big bold text saying it didn't kill viruses, which is normally not a concern for the type of water sources you encounter in national parks (at least in the US).

Edit: Changed "UVP" to "UV Pen" to clarify.

Not at all, trust it entirely on clear water. The UVC tech is very effective, they've got nice technical papers on it. And it's widely used for larger scale water treatment and very well understood.

If anything, the convenience is a factor in drinking more. It's so easy that I can do a bottle on a quick rest stop by a stream. I leave it handy so maybe 30 seconds to pull it out, and a minute for the uv to shine. (For muddy water it should be filtered enough first to make it clear, but I don't experience that.)

I've been building a post-apoc survival adventure game lately [1], so this story is absolutely relevant to my interests. Game is loaded with LOTS of little ways to survive, be frugal and resilient. And all the painful trade-offs you sometimes have to make.

Water is a huge part of life. We need it for almost everything we do as human beings. Drinking, preparing food and eating, cleaning and bathing. You can play in it, it looks and sounds relaxing. And make ice cubes to chill drinks! Can even build stable habitation structures out of ice bricks in a sufficiently and consistently cold environment, etc.

Water... what can't it do?

----

(1. see my bio: Slartboz)

This seems like an effective way to kill microbes without using chemicals that could be harmful to humans. And the reusability aspect is great. But does anyone know if the hydroxyl radicals/hydrogen peroxide used to destroy the cell membranes would have an impact on the shiga toxin? Also it sounds like it takes up to 30 min to kill all viruses at 3% H2O2.

Why can't we just blast the water with a lot of UVC, then add some chlorine or something as we do now??? I don't want any nanoparticles that could potentially leak past the magnet, deposit in my skin, and make toxins if I go in the sun.

We could probably make a whole lot of UVC LEDS for cheap if we scaled production. Plus, we already have lots of ways to filter. Is this really gonna be that much cheaper? The world has plenty of resources, seems like we could give people clean water with current tech.

Can't titanium dioxide make hydrogen peroxide too? Why does it have to be stirred in the water? Can't we have something bound to a surface for the light to hit?

If you’re in a place without clean water, chances are pretty good you’re also in a place without electricity to run UVC lamps.

But if you can bring in a nanoparticle based plant or distribute the equipment you can probably bring in some solar panels and batteries for a bit more cost, that probably would be reasonable for whatever country or group is sending this stuff, if someone really wanted to.

Many armies have rations that contain tablets to disinfect water. But they don't need sunlight. Wonder how is this one better.

>Wonder how is this one better.

"Conventional water-treatment technologies include chemicals, which can produce toxic byproducts, and ultraviolet light, which takes a relatively long time to disinfect and requires a source of electricity."

Little hand pumps or even filter straws exist too. Handy for camping but they will freeze.

Looks like it's reusable. You use a magnet to collect the powder and it goes into more dirty water again.

"Disinfectant powder is stirred in bacteria-contaminated water (upper left). The mixture is exposed to sunlight, which rapidly kills all the bacteria (upper right). A magnet collects the metallic powder after disinfection (lower right). The powder is then reloaded into another beaker of contaminated water, and the disinfection process is repeated"

Yeah, iodine tablets. I used to use them for caving and backpacking. Some people say it tastes bad but never bothered me. Is there some claim that they are harmful?

>Some people say it tastes bad but never bothered me.

I feel like those people are missing the point.

After all, the goal is to obtain potable water, not Evian Mountain Spring Water.

>Each tablet contains 20 mg of Tetraglycine Hydroperiodide (TGHP) which liberates 8 milligrams (ppm) of titratable iodine. Diatomic iodine (12) and hypoiodous acid (HIO) are the most prevalent entities.

https://www.quakekare.com/water-purification-tablets-p-23

>in some people, excess iodine intakes may precipitate hyperthyroidism, hypothyroidism, goiter, and/or thyroid autoimmunity.

https://pubmed.ncbi.nlm.nih.gov/30891786

>Iodine toxicity may lead to thyroiditis, hypothyroidism, hyperthyroidism, and thyroid papillary cancer.

https://pubmed.ncbi.nlm.nih.gov/32809605/

It seems like you'd have to ingest A LOT of this stuff to have problems, though.

Actually it's possible that small amounts of added iodine can cause hashimoto's thyroiditis. A 20 year study in Denmark found that adding iodine to table salt led to more hypothyroidism:

https://academic.oup.com/jcem/article/104/5/1833/5244187

How does this apply to people who consume extra iodine via natural sources like seaweed? I thought that was beneficial for thyroid health.

You can easily remove the taste with ascorbic acid. Not sure what that does to the bioavailability of the iodine though.

key quotes imo:

> The powder consists of nano-size flakes of aluminum oxide, molybdenum sulfide, copper, and iron oxide.

or, from the paper, "discrete nanoflakes of (Al2O3@v-MoS2)/Cu/Fe3O4"

> “The materials are low cost and fairly abundant. The key innovation is that, when immersed in water, they all function together.”

> The nontoxic powder is also recyclable. Iron oxide enables the nanoflakes to be removed from water with an ordinary magnet.

> The chemical byproducts generated by sunlight also dissipate quickly.

I'd be curious to learn more about potential byproducts. Seems like the study focused on only a few types of wastewater. In practice it'd have to handle a much larger variety of chemical and biological constituents

Haven’t iodine tablets been around for a long time? Why is this better?

It seems that the water should be distilled, otherwise the process will not be as predictable as it is described ...

OK, so now what? FDA testing? Will this be in the backpacking store soon? Bigger versions for home use?

So far this group only tested this solution on E.coli. This sounds very encouraging, but many more studies are needed, I would guess. So maybe not in the store tomorrow, but overall quite promising.

does overcast light work? I'm thinking of places where you don't see actual sunlight for weeks at a time. Like the outer Richmond

Molybdenum and copper are harmless??

From the team that brought you microplastics in the brain, a hot new summer release. Metal powder in the brain!

Better not eat Spinach (2.7 mg per 100 grams).

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