AJKOER
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Microwave Assisted Galvanic Bleaching with Dilute H2O2, Cu Metal, NaHCO3, NaCl and Graphite
This is actually the case of my annoying tea-stained mug that, with conventional scrubbing, was totally ineffective. The position of the tea stain on
the mug was largely near the interface of air/water where the tea bag was placed upon numerous microwave-based heating episodes (so a tough stain).
After attempting scrubbing, I added some Baking Soda to the scrubbing exercise. Still, little to no progress, so I further introduced some Apple Cider
Vinegar to the mix, whereupon, the stain may have actually got a little bit darker!
Next, I found an old previously open bottle of 3% H2O2, from which, I applied around 25 ml. Still nothing.
My last successful effort surprisingly used a relatively weak bleaching composition consisting of more H2O2, a copper penny, sea salt, a graphite rod
(for mechanical pencils) and added distilled water (filling the mug above the stain), all subject to 3 minutes of microwaving, that produced effective
bleaching results!
Outline of Suggested Chemistry At Work
Given that conventional scrubbing, baking soda, and vinegar, collectively, were not able to remove the tough tea stain, I favor a radical pathway as
the most likely pathway. As such, my opinion on possible reaction pathway to account for the bleaching action includes:
> Starts with Copper metal readily donating an electron, especially in a galvanic cell:
Cu -> Cu+ + e-
> Per ScienceDirect (see https://www.researchgate.net/figure/One-electron-and-four-el...), to quote:
"One-electron reduction of H2O2 forms a hydroxyl radical (HO•) and hydroxyl anion"
As depicted in the reaction:
H2O2(aq) + e-(aq) -> HO• (aq)+ OH- (aq)
> Further, Copper/Cuprous can feed a Fenton-like reaction creating the HO• radical per the reaction (reference: see for example, https://pubs.acs.org/doi/10.1021/es00162a012):
Cu/Cu+ + H2O2 ⇄ Cu+/Cu++ + HO• + HO-
> And also, the action of the hydroxyl radical (HO•) with bicarbonate can form the powerful reducing carbonate radical anion (CO3•-) via:
HO• (aq) + HCO3- (aq) -> H2O (l)+ CO3•- (aq)
Source: See https://tspace.library.utoronto.ca/handle/1807/14631 and also on iron (not copper) based Fenton, see, https://www.sciencedirect.com/science/article/abs/pii/S08915... .
Also, a related article, "Influence of bicarbonate and carbonate ions on sonochemical degradation of Rhodamine B in aqueous phase", employing a
different path to the HO• radical but leading similarly to the CO3•- radical, with respect to dye degradation, to quote:
"The influence of bicarbonate and carbonate ions on sonolytic degradation of cationic dye, Rhodamine B(RhB), in water was investigated. As a
consequence of ultrasonic cavitation that generates •OH radicals, carbonate radicals were secondary products of water sonochemistry when it contains
dissolved bicarbonate or carbonate ions."
> Finally, the copper/carbon galvanic cell was further accelerated by microwaving (see, for example, this source on a microwave-assisted reaction
at https://pubs.acs.org/doi/10.1021/ar400309b)
In conclusion, my opinion on this successful bleaching action may have wider implications on bleaching applications than the case described herein,
being an example of a Galvano-assisted reaction.
Note: Only minor anodic corrosion on the copper penny was observed (mainly, on one side of the penny).
[Edited on 17-6-2023 by AJKOER]
[Edited on 17-6-2023 by AJKOER]
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AJKOER
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Image of starting stain
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AJKOER
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End of treatment
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Sulaiman
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Eye of newt and toe of frog, Wool of bat and tongue of dog…
So many variables,
I guess not too easy to properly understand
without quite a few experiments?
CAUTION : Hobby Chemist, not Professional or even Amateur
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unionised
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Can you rule out the simple idea that warm/hot peroxide bleached the stain?
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Texium
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Thread Moved
17-6-2023 at 04:36 |
Texium
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This isn’t science
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AJKOER
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???
Years ago when one searched on "Galvanic Synthesis", the results returned were dated works on relatively simple galvanic-based synthesis.
Not today, here is what you get to quote a sample:
"Amongst the methods developed to produce nanoparticles in solution, galvanic reactions between metallic nanoparticles and metal ions have
been proven as a versatile approach from which a wide range of nanoparticles, ranging from AgPd, AgPt, AuCu nanoalloys and hollow AgAu nanocages could
be engineered [19-21]."
and who is generating this "non-science", nobody you know apparently. Some detail, as an example, and please do not search yourself, it only gets more
embarassing.
"Indium hydroxide/silver/carbon nanocomposite: Synthesis via galvanic reaction between In nanoparticles and silver nitrate, characterization and its
photocatalytic activity"
by Pui Munn Wong, a,Teck Hock Lim, Joon Ching Juan and Jau Choy Lai, Faculty of Applied Sciences, Tunku Abdul Rahman University College, Kuala Lumpur,
Malaysia Nanotechnology & Catalysis Research Centre, University of Malaya,, Kuala Lumpur, Malaysia Faculty of Chemical & Energy Engineering,
Universiti Teknologi Malaysia, Skudai, Johor, Malaysia
Apparently, more recently, galvanic synthesis has also been discovered as a unique important approach relating to paths for improved nano synthesis.
[Edited on 17-6-2023 by AJKOER]
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Texium
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Cool, but that has nothing to do with your own shoddy experiments. These papers you cite are using much more advanced methods and more rigorous
experimental control than anything you have ever done. You really think tossing a copper penny and a piece of pencil graphite in a cup is somehow
comparable to precisely engineered metal nanoparticles? Absolutely bonkers. You don’t follow the scientific method whatsoever. You performed no
controlled experiments. You haven’t proven anything, and I bet if you ever had the chance to share your “findings” with your heroes, they’d
laugh you out of the room.
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AJKOER
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Quote: Originally posted by Sulaiman  | Eye of newt and toe of frog, Wool of bat and tongue of dog…
So many variables,
I guess not too easy to properly understand
without quite a few experiments? |
Okay back to chemistry and not Harry Potter, and interesting aspect of a galvanic approach to standard chemical techniques is importantly that a
galvanic synthesis completely resides in electrochemistry. For example, rusting in moist CO2-loaded air of an iron nail (anodic oxidation of an iron
alloy) is a function only of any available iron metal with any surface area exposure along with a supply of oxygen in moist air. The actual chemical
concentrations of any of these elements (other than zero) is not material, and the reaction precedes in the order of the anodic index of the metal in
question based upon surface area considerations. However, this is not to say that you could obtain other metal ions in solution, as once iron is
removed, the next element in the alloy will be subjected to anodic corrosion, and its ions will then orderly enter the solution also. So a key
procedural part of galvanic-based chemistry is not to let the reaction proceed so long that the next element gets introduced.
Another cool advantage of galvanic-based chemistry is that if you have a surprise visit from local law enforcement (because your neighbor has noticed
you doing chemistry in your garage), they will not find bottles of potent mineral acids to present to a jury for your explanation. These acids can
(and, in general, as per a family scenario) present safety concerns, and I select to mostly avoid them.
What is also nice is that even if your metal, say a copper source, is an alloy, as long Cu has the highest anodic index, it will be attacked/dissolved
first (and it only, until it is depleted). In other words, with a galvanic synthesis approach, you may be able to achieve a 100% pure salt of the
first anodic element with many alloy sources of copper.
However,, the down-size of this science, is, for example, one must understand the galvanic cells release electrons and, for example, what does that do
in the presence of mild weak H2O2 ? It actually converts it into a powerful radical (see chemistry cited above) that would readily attack a metal M
surface forming in the case of the powerful hydroxyl radical, the salt MOH. So, you added acid source need now only be strong enough to attack MOH and
not metal M. I have actually reported on this forum the successful dissolving of a tungsten metal filament without the use of any superacid (more like
a transient super radical).
[Edited on 17-6-2023 by AJKOER]
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chloric1
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| Quote: Originally posted by Texium | | Cool, but that has nothing to do with your own shoddy experiments. These papers you cite are using much more advanced methods and more rigorous
experimental control than anything you have ever done. You really think tossing a copper penny and a piece of pencil graphite in a cup is somehow
comparable to precisely engineered metal nanoparticles? Absolutely bonkers. You don’t follow the scientific method whatsoever. You performed no
controlled experiments. You haven’t proven anything, and I bet if you ever had the chance to share your “findings” with your heroes, they’d
laugh you out of the room. |
I hear and understand your point but you come off a little exclusionary and downright nasty. I do not approve. I would simply ask the OP to repeat
the experiment by leaving out each variable until he determined what the correct active component is working here. Keep in mind the greatest minds in
centuries past had almost nothing to work with. Not everyone has access to a fully stocked lab. Furthermore, I’d like to encourage this individual
to continue to learn and explore and fine tune his scientific method in his experiments. I mean at least he is seeking peer reviewed articles and
not just sloppily working blind.
Fellow molecular manipulator
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Tsjerk
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| Quote: Originally posted by chloric1 |
I hear and understand your point but you come off a little exclusionary and downright nasty. I do not approve. I would simply ask the OP to repeat
the experiment by leaving out each variable until he determined what the correct active component is working here. Keep in mind the greatest minds in
centuries past had almost nothing to work with. Not everyone has access to a fully stocked lab. Furthermore, I’d like to encourage this individual
to continue to learn and explore and fine tune his scientific method in his experiments. I mean at least he is seeking peer reviewed articles and
not just sloppily working blind. |
Sure, but this is AJOEKER we are talking about here. He has an extensive history were he claims wild things, and from experience we all know he is not
going to repeat or control any experiment.
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AJKOER
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Chloric1:
You are 100% right in citing my 'working blind.'
I tried obvious simple routes to address my stained mug with no thought that I would be possibly reporting my adventure.
Unfortunately (or is that fortuitously), I resorted to a galvanic approach in a last attempt to only 'discover' how good it worked!
Such, I suspect, is not a strange event in the course of the history of science.
As I do not have any more significant tea stains, it may take so time to repeat, but others are invited to revisit and read up on the science I have
cited.
Also Texium:
On your claim that the galvanic nano cited application is not related, re-visit my Fe rusting discussion, and just replace Fe metal with ferrous (the
start of the second stage in actual rust, ferric oxide, formation) that involves further oxidation to ferric, which is closer to the path cited
starting with an existing nanocrystal that is hollowed out (via galvanic corrosion), per my understanding.
[Edited on 17-6-2023 by AJKOER]
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chloric1
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Next up….chromatography with a Kotex!
Fellow molecular manipulator
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DraconicAcid
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The joker would wrap it in copper wire and put it in the microwave for the duration of the experiment.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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AJKOER
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Found an interesting supportive reference provided by ScienceDirect "Oxidation of dyes from colored wastewater using activated carbon/hydrogen
peroxide" here https://www.sciencedirect.com/science/article/abs/pii/S00119... , to quote:
"Advanced oxidation processes (AOPs) using strong oxidants such as hydroxyl radicals (HO•) are an emerging technique to degrade pollutants in
aqueous media. Hydroxyl radicals can be produced from H2O2 using homogeneous (e.g. Fenton reaction) or heterogeneous catalysts (supported metal
catalysts, metal oxides, graphite and activated carbon (AC)) [11]."
Note, the mention of both Fenton (inclusive, I would argue of also Fenton-like Copper chemistry, as I cited previously) and also graphite, to quote
further on mechanics:
"Other than this direct decomposition reaction, it is commonly accepted in the literature that H2O2 can be activated on the AC surface to generate
hydroxyl free radicals [11], [15], [19]. The AC can be regarded to function as an electron-transfer catalyst just like the Haber–Weiss mechanism
involving the reduced (AC) and oxidized (AC+) catalyst states (Reactions (1), (2)) [11]....With a high oxidation potential (Eo) of 2.80 V, the HO•
is a highly reactive species that can nonselectively degrade and rapidly mineralize a variety of refractory compounds into smaller and more
biodegradable ones such as CO2 and H2O [11], [22]."
which confirms many of my prior statements, equations and also cited references. Also with respect to graphite itself an article "Microwave-Assisted
Reactions on Graphite" at https://onlinelibrary.wiley.com/doi/abs/10.1002/3527601775.c... .
[Edited on 17-6-2023 by AJKOER]
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Tsjerk
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Yes, or read a little less literature and bleach a tea stain with plain hot H202.
Btw; hot vinegar also works, as does hot citric acid.
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AJKOER
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| Quote: Originally posted by Tsjerk | Yes, or read a little less literature and bleach a tea stain with plain hot H202.
Btw; hot vinegar also works, as does hot citric acid. |
Thanks for this, as I also found a web reference claiming simply hot aqueous NaCl works on your more normal tea stain as does vinegar, but my Apple
Cider Vinegar produced none to negative results on my stain, as I reported in my opening thread!
I suspect the position of my tea-induced stain (surface/air contact) with the water-saturated tea bag being microwaved may not result in your typical
tea stain.
Research per Wikipedia on Tannic acid at https://en.wikipedia.org/wiki/Tannic_acid supports uncertainty, to quote:
"The chemical formula for commercial tannic acid is often given as C76H52O46, which corresponds with decagalloyl glucose, but in fact it is a mixture
of polygalloyl glucoses or polygalloyl quinic acid esters with the number of galloyl moieties per molecule ranging from 2 up to 12 depending on the
plant source used to extract the tannic acid. Commercial tannic acid is usually extracted from any of the following plant parts...."
So tea, itself, appears to be chemically not very definite, how the tea is heated/prepared, and further processing (removing caffeine), adds
uncertainty as to whether was my tea stain even typical?
[Edited on 17-6-2023 by AJKOER]
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Rainwater
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Not sure if this is the same as tea stains, but I add protein powder to my coffee thermos, (2 birds 1 drink), it stains cups and does not wash off without stealwool and elbow grease.
"You can't do that" - challenge accepted
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Tsjerk
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| Quote: Originally posted by AJKOER |
but my Apple Cider Vinegar produced none to negative results on my stain, as I reported in my opening thread!
[Edited on 17-6-2023 by AJKOER] |
I read that, but did you heat it?
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AJKOER
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Tsjerk: No, I did not heat it, because the amount of solution would be difficult to place/keep on the stain (see picture).
Perhaps in the future, I (or others) could try cotton soaked with H2O2, NaCl,..., as a topical hot treatment stain remover.
Interestingly, my ultimate procedure suggests to me perhaps also a chemically related process (that is more convenient, reagent-cheap, and safe)
providing a path to the powerful (and transient) HO• radical as a more general bleaching/disinfecting protocol for all.
[Edited on 18-6-2023 by AJKOER]
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unionised
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AJKOER
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No, however, here is a comment on how to remove tea stains from the interior of a MW oven, to quote:
"GE recommends placing a glass bowl with a cup of water and a tablespoon of lemon juice in the microwave and heating it until it is steaming. This
should help loosen whatever is on the oven's interior. Then scrub the interior with a damp cloth and baking soda"
The curious part, in my opinion, is "help loosen" as clearly my stain was baked in, and the surface presented a good shine, so in essence, nothing to
loosen here if that was the usual purpose of this suggested composition (which has also been previously cited).
And, the article "Why You Should Never Microwave Tea—Plus the Right Way to Brew It" at https://www.realsimple.com/food-recipes/cooking-tips-techniq... , which is of the opinion, to NOT use a MW for tea preparation, as it claims to
impact the quality of the heated tea drink (which may suggest a tastable chemical alteration). Or, in other words, a bit more of chemistry that is
not particularly palatable to your culinary tea expert.
To cover all bases, one could even expand the very origin of the 'stain' itself to a possible case, for example, involving a microwave-assisted anodic
reaction at the air/solution interface on the porcelain surface.
[Edited on 20-6-2023 by AJKOER]
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Tsjerk
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| Quote: Originally posted by AJKOER |
The curious part, in my opinion, is "help loosen" as clearly my stain was baked in, and the surface presented a good shine, so in essence, nothing to
loosen here if that was the usual purpose of this suggested composition (which has also been previously cited).
[Edited on 20-6-2023 by AJKOER] |
That is one radical assumption, assuming your stain was baked in. There is no reason to think your stain was any different from other stains, or to
think normal methods wouldn't have worked to remove it. You just didn't try any other method besides the concoction you claim to work via some
galvanic mechanism (which you did zero controls for).
| Quote: Originally posted by AJKOER |
And, the article "Why You Should Never Microwave Tea—Plus the Right Way to Brew It" at https://www.realsimple.com/food-recipes/cooking-tips-techniq... , which is of the opinion, to NOT use a MW for tea preparation, as it claims to
impact the quality of the heated tea drink (which may suggest a tastable chemical alteration). Or, in other words, a bit more of chemistry that is
not particularly palatable to your culinary tea expert.
[Edited on 20-6-2023 by AJKOER] |
This article clearly states different teas need different temperatures and in a microwave you can't control the temperature. Nothing to do with
chemical alterations, but with temperature of extraction.
| Quote: Originally posted by AJKOER |
To cover all bases, one could even expand the very origin of the 'stain' itself to a possible case, for example, involving a microwave-assisted anodic
reaction at the air/solution interface on the porcelain surface.
[Edited on 20-6-2023 by AJKOER] |
You are doing exactly what you are always doing; running ahead of the process, starting at the end, coming up with bizarre, unfounded and unnecessary
explanations for problems you could have simply solved at the beginning by following the scientific approach, as mentioned above.
[Edited on 20-6-2023 by Tsjerk]
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