How can "chemical-free" surface cleaners work?

Question

There's a company called 2San that has gotten some press recently for selling a "chemical-free" cleaner, which is "created by re-engineering water in a seven-stage filtration process". It's called Clean Zero.

The marketing materials state:

Clean Zero is produced through microfiltration of water, and provides cleaning and sterilisation to a hospital grade standard. The product is ideal for all daily cleaning tasks on water washable surfaces – the ingredients are naturally derived, making it 100% sustainable.

The seven-stage process begins with the removal of elements such as chlorine, grit, and other inorganic compounds such as calcium that are naturally found in water. The water is then purified in a process that uses a partially permeable membrane to dispose of the unwanted contaminants and molecules before the final stages of hydro-embellishment. The composition of Clean Zero is unstable and therefore it performs a mechanical action when applied to surfaces, enabling it to absorb dirt and contamination. The result is a clean, streak-free surface without any residue.

As Clean Zero eradicates 99% of bacteria and viruses including COVID-19 in two seconds, there is no need for a separate sanitiser to be used.

This product is now being used by a government-owned train operator in the United Kingdom. The company sells the cleaning solution in both bottle form, and manufactures kit that can apparently provide you with an endless supply of it.

Ignoring the fact that water is clearly a chemical compound, I don't understand how this works. Is it just filtered water? What is "hydro-embellishment"?

I was under the impression distilled water wouldn't have any sterilising activity/antimicrobial properties^[1], so how is it actually achieving sterilisation?

[1]: Burton, Maxine et al. “The effect of handwashing with water or soap on bacterial contamination of hands.” International journal of environmental research and public health vol. 8,1 (2011): 97-104. doi:10.3390/ijerph8010097

Answer 1

It's probably not ozone.

Or if it is, they're lying about the shelf life of their product.

Laurel's answer suggests that Clean Zero might be ozonated water, i.e. pure water mixed with small quantities of ozone (O₃). Ozonated water is an actual substance that can be produced on demand from air and purified water and used as a disinfectant.

However, ozone is an unstable and highly reactive substance that decays quite rapidly in water. Even under ideal circumstances (cold and very pure water) the half-life of ozone in water is only about 30 minutes, meaning that only 50% of the original ozone remains after 30 minutes, only 25% after 1 hour, only 6.25% after 2 hours and so on. Further, if the water is warmed up to room temperature or contains trace impurities that can react with the ozone, the half-life reduces to just a few minutes.

This is blatantly incompatible with Clean Zero's assertion that their product has an active shelf-life of several months. In particular, the Clean Zero website's page for their 500 ml plastic "Ready To Use Sprayer" bottles says (emphasis mine):

When required, simply fill directly from your Clean Zero 20, Clean Zero 80 or Clean Zero Hi-Vol unit and use on surfaces such as worktops, mirrors, washroom fittings and touch points. Store away from direct sunlight and your Clean Zero will remain active for a minimum of 10 months.

If Clean Zero is ozonated water, there won't be any detectable ozone left in it after storing it in a plastic bottle for 10 months (or even 10 hours), whether in direct sunlight or not.

It could be hydrogen peroxide.

Dilute solutions of hydrogen peroxide (H₂O₂) in water are also commonly used as disinfectants and they can be produced from oxygen and water using electricity and a solid catalyst.

While hydrogen peroxide is also unstable and naturally decomposes back into water and oxygen, it is significantly more stable than ozone. Under ideal conditions dilute hydrogen peroxide may decay by less than 0.5% per year but its decay can be accelerated by various factors, including both high temperature and the presence of catalytic impurities as well as exposure to air and to ultraviolet light (including sunlight). When stored in an unopened bottle and away from sunlight, commercially available hydrogen peroxide solutions can remain effective for up to 3 years, but opening the bottle and exposing the solution to air can reduce its effective lifetime to just a few months.

Of course, all this depends on both the original composition of the peroxide solution (including whether it contains any chemical stabilizers that slow down the decay), the way it's stored and — last but not least — on what you define the minimum effective concentration of remaining peroxide to be. Still, just as a random data point, this commercially available 1.4% hydrogen peroxide disinfectant spray is advertised as having a shelf life of 24 months, which is comparable to the 10 month active life advertised for Clean Zero. The difference between 10 and 24 months may plausibly come down to different initial peroxide concentrations, different storage conditions, different efficacy standards and/or the presence of stabilizer chemicals in the off-the-shelf product.

It might just be water (and snake oil).

All that said, I cannot rule out the possibility that Clean Zero is simply nothing but purified water. Indeed, their marketing materials seem to go to great lengths to suggest that their product contains nothing but pure "chemical free" water, somehow magically "embellished" to become an effective cleaning agent.

However, it's worth noting that just wiping a dirty surface with clean water (and a clean cloth) can be enough to remove a fairly large fraction of organic contaminants (including viruses, bacteria and other microorganisms) on it, especially if the surface itself is relatively non-porous and the dirt on it is not particularly oily or stuck to the surface. While water alone is not usually considered an effective disinfectant, I cannot rule out the possibility that, under sufficiently favorable testing conditions, it might show a measurable effect on ATP test results, which is what Clean Zero seems to be basing its efficiency claims on.

Update: The material safety data sheet for Clean Zero located by grafix, if confirmed to be accurate, pretty much confirms this option. The only substance listed in section 3 of the data sheet as being present in the product is distilled water. If ozone, hydrogen peroxide or any other reactive substance was included in the Clean Zero solution, it would legally have to be listed on the data sheet.

(FWIW, I very much doubt they would lie about the composition of their product on the official data sheet, since doing so would attract the attention of government agencies that take that kind of stuff very seriously and open them to legal action that would be very hard for them to weasel out of — much worse than, say, making dubious marketing claims.)

Answer 2

The "chemical-free" ingredient is probably ozone (O₃), a disinfectant

The first steps of the process are to filter and purify the water, including with reverse osmosis. Unfortunately, even after poring over dozens of pages about the cleaner and the devices that make it, I could not find any actual disclosure of what the "final stages" of the treatment process are. The writing has clearly been "hydro-embellished" with marketing speak and has very few solid details. Nonetheless, the following statements stand out:

1. It's "unstable", leaves no residue, and is also environmentally friendly
2. The Clean Zero 80 Cabinet, which makes the liquid, only needs a source of water (and new filters, as needed)
3. It's apparently more effective at cleaning than just water
   • It kills bacteria and viruses according to the quote in question
   • According to a study done by the company, it replaced "Stainless Steel Cleaner, Glass/Mirror Cleaner, General Multi- Purpose Cleaner and a Disinfectant Cleaner"
4. It's not hazardous to consume, though they say specifically not to
5. It's described as "re-engineered water"

Ozonated water seems like a solid match for this, point for point. According to Ozone Water Is an Effective Disinfectant for SARS-CoV-2:

1. The residual ozone in the water can be decomposed rapidly and converted to oxygen within a short period (typically within 30 min) under natural conditions. This feature is highly valuable for food disinfection.

2. Secondly, an ozone water generator's price is usually as low as 8,000 Yuan in China, which can convert tons of tap water into ozone water in less than 30 min. [...]

   Filters are used in devices like these to filter out compounds (like bromide) that may react poorly with ozone. This is likely also the reason they emphasize the purification process and advise not mixing the cleaner with anything.

3. Cleaning:

   • Thirdly, SARS-CoV-2 can be inactivated by ozone water within 1 min, which is very efficient. In addition to ozone water, other studies also showed that ozone gas is highly effective in eliminating SARS-CoV-2.

   • More from The Strategist: "according to studies cited by [environmental consultant Brian] Oram, that aqueous ozone can break down a large array of bacteria, viruses, and protozoan, including E. coli and salmonella, in addition to odors and soil molecules."

4. Though the health benefits of doing so have been debated, it has been drunk directly and is also used as a disinfectant for food and water. See What Is Ozonated Water, and Can You Drink It?

5. Ozonated water is a type of "engineered water". Other types of engineered water can clearly be ruled out, like steam.

Answer 3

The manufacturer’s data sheet suggests that Clean Zero is just distilled water.

The relevant section is "Section 3: Composition Information on Ingredients":

3.1 Chemical Characterisation: Substances

• CAS No. Description 7732-18-5 water, distilled, conductivity or of similar purity
• Identification number(s) EC number: 231-791-2

Those numbers are consistent with purified water. Further, physical data is quoted that tracks with pure water. However, some information is more concerning, such as "Section 4: First Aid Measures":

4.1 Description of First Aid Measures
[...]

• After eye contact: Rinse opened eye for several minutes under running water.

I would posit that this is standard advice given for almost all chemicals and most likely the result of the template.

Answer 4

Let's assume that the water is "chemical-free" in the sense that it contains no chemicals in addition to those normally in water. Water is normally in equilibrium with surrounding gases (air) and there is normally a gas-water interface that has significance to cleaning. For example, trace organics which may contaminate water will tend to accumulate at the gas-water interface, and for this reason one step to produce highly pure water is to allow small bubbles to pass through it and then skim them off from the surface.

The gas-water interface is also thought to accumulate charged species, such as those normally in equilibrium with H2O (hydroxide, hydronium, etc...) or naturally present mineral salts.

I googled "nanobubble cleaning" and found this commercial site among others, and this scientific paper by a well-respected expert in the nanobubble field, which explains some of the principles.

The method of producing bubbles which last long enough for cleaning might involve electrolysis or extreme mixing, cavitation or filtration. Though these processes may introduce transient chemical species, if they are not long-lasting then it might be justified to say that the water is "chemical-free" since it would only contain what is normally in water and bubbles.

Answer 5

Is it Electrolyzed Oxidized (EO) Water

Apparently, if current runs through water, you can get a cleaner and a disinfectant.

EO water is created when a saltwater solution goes through an electrolysis process, which separates the water’s positive and negative ions. This makes two forms of water: one very acidic and one very alkaline.

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