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Author: Subject: Removing HCl from aqueous CuCl2 Without Heat or Cl2 Formation
AJKOER
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[*] posted on 1-2-2022 at 08:38
Removing HCl from aqueous CuCl2 Without Heat or Cl2 Formation


This question was actually asked elsewhere, but I have decided to post a likely correct answer as developed /reviewed on this forum and will refer the party who asked.

First case, assume the HCl is likely dilute, in which case, cannot just consider adding CuO, as per my experience, it is somewhat inert especially on aging along with a reference claiming CuO is: "Assay, Insoluble in Dilute Hydrochloric Acid", available here https://pubs.acs.org/doi/10.1021/acsreagents.4106 . Also, my research suggests perhaps CuO may be reactive enough to induce a visible coloration effect with dilute HCl acting on the CuO, but not a significant dissolving or neutralization effect, as is required here.

As such, the dilute HCl case answer proposed is simply adding pieces of copper metal (in excess with air contact), with beneficial light exposure to the aqueous cupric chloride and HCl in a shallow wide-mouth inert vessel exposed to an oxygen source (air or dilute H2O2).

Likely most fundamentally here is the electrochemical based corrosion of copper metal https://opentextbc.ca/chemistry/chapter/17-6-corrosion/ in the presence of an oxygen source and acid (paralleling the so-called rusting of iron) which normally forms a mixed oxide/carbonate layer (see Wikipedia on Patina here https://en.wikipedia.org/wiki/Patina ), that here is neutralized by the excess HCl presence (albeit, the electrochemistry can be a slow process, but I expect, per below, possible light based assisted acceleration):

2 Cu + O2 + 2 H+ -> Cu2O + H2O (an electrochemical reaction)

Cu2O + 2 HCl -> 2 CuCl + H2O

This experiment possibly also likely benefits from photochemistry around natural light as CuCl2, apparently, has photosensitive properties (see, for example, this source https://inaoe.repositorioinstitucional.mx/jspui/bitstream/10... , which interestingly parallels photocatalytic Ferric Chloride discussed here https://www.infona.pl/resource/bwmeta1.element.elsevier-df6d... ). As such, application of especially strong light may create solvated electrons, which can attack/remove with time the H+ in solution, leaving Cl-.

H+ (aq) + e- (aq) -> •H (aq)

•H (aq) + •H (aq) -> H2 (g)

•H (aq) + O2 (dissolved) -> •HO2 (aq)

•HO2 (aq) + •HO2 (aq) -> H2O2 (aq) + O2 (g) (slow reaction)

... and more (including loss of HCl from evaporation/warming from light)

where we have progressed into radical reactions which can lead to even more advanced chemistry relating to Fenton-like reactions with respect here to copper noted, for example, in this article "Fenton-Like Reaction between Copper Ions and Hydrogen Peroxide for High Removal Rate of Tungsten in Chemical Mechanical Planarization" https://iopscience.iop.org/article/10.1149/2.0131803jss#:~:t... for those interested.

In the rich standard chemistry around copper complexes, expect the formation of a green/yellow CuCl4(2-) ion in the presence of HCl:

CuCl2 + 2 Cl- -> CuCl4(2-)

And, with copper metal:

Cu + CuCl4(2-) -> 2 CuCl2-

where the last complex contains cuprous and is colorless. Further, this complex can react with remaining cupric in solution, rendering a dark brown mixed-oxidation state complex, having simplified formula ClCu(μ-Cl)CuCl, with an ascribed oxidation state of +1½.

Finally, as the acid is removed, expect just aqueous CuCl2 represented by a blue hydrated cupric ion.

Should be quite an interesting experiment (actually based on observations reported on SM by Woelen here http://www.sciencemadness.org/talk/viewthread.php?tid=82313 for aqueous CuCl2 in HCl) which, as I have noted, also can encompass a wide range and depth of chemistry.

On the case of strong HCl (albeit, I suggest not a likely case, as even if one started to prepare this aqueous CuCl2 from strong HCl, adding dilute H2O2 to act on Cu, no longer implies a strong residual acid presence), one might try stirring and moderate warming to remove the excess HCl via CuO addition.

If anyone has comments on my suggested path or other ideas, please contribute.

[Edited on 2-2-2022 by AJKOER]
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AJKOER
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[*] posted on 1-2-2022 at 09:31


A comment on photosensitive CuCl2, not likely as good as FeCl3 (discussed recently in this SM thread http://www.sciencemadness.org/talk/viewthread.php?tid=158266 ), but also incidentally mentioned, in that thread, is that both Fe and Cu ion presence are both apparently responsible for accelerated hypochlorite bleach decomposition (turning into H2O, NaCl and NaClO3), especially upon light exposure!

Also, anyone having experience working with fresh vs aged CuO, I would appreciate comments.

[Edited on 1-2-2022 by AJKOER]
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[*] posted on 1-2-2022 at 13:12


I've quite easily gotten crystals of HCl-free CuCl2 dihydrate by simply evaporating the solution until nearly dry, then putting it in a desiccator over anhydrous sodium carbonate. Within two days it was dry and acid-free. No need to make a wall of text invoking radical chemistry. And once again, the sources that you cite do not actually support your far-fetched and over complicated claims.



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AJKOER
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[*] posted on 1-2-2022 at 16:24


Yes, thanks Texium for your comments.

Not really complex, main reaction is the "rusting" of metal copper in the presence of air and an acid source. The creation of patina has long been known.

As to the photochemistry here, it appears to be real (both Fe and Cu impurity in your bleach with light exposure is widely reported to speed decomposition, see discussion here http://www.sciencemadness.org/talk/viewthread.php?tid=158266).

As to the Fenton-like copper chemistry, likely a bad idea to dismiss and per below, appears helpful in explaining chlorine formation.
================

Apparently the party asking for a "no boiling" solution here does not have either permission to access household appliances or otherwise heating equipment/space to provide ventilated warming.

So, this provides an interesting constraint to what I might describe as "caveman chemistry".

I also remember a concern over possible chlorine formation (will go back and check), which could be noticeable in even small amounts.

My extended review of the chemistry does indicate a potential path to some chlorine, that from a recent chemistry perspective is quite interesting. Proceeding from where I stop at the •HO2 radical creation in the present of solvated electrons from photo-activated aqueous CuCl2, the following reactions:

•HO2 + •HO2 = H2O2 + O2 (albeit, a reportedly slow reaction)

•HO2 + e- -> HO2-

H+ + HO2- = H2O2

where the last two photo-assisted reactions could be fast. Further, some recent chemistry: "Copper ions and hydrogen peroxide form hypochlorite from NaCl thereby mimicking myeloperoxidase"at https://pubmed.ncbi.nlm.nih.gov/3009503/ , and http://pubs.rsc.org/en/content/articlelanding/2016/cc/c5cc07... ).

There could be indeed a Fenton-like reaction between a soluble cuprous complex and H2O2 forming hydroxyl radicals which could lead to some hypochlorous acid:

Cu(l) + H2O2 --> Cu(ll) + •OH + OH-

HCl + •OH = •Cl + H2O (recently confirmed, see this 2015 work: "Mode Specificity in the HCl + OH → Cl + H2O Reaction: Polanyi’s Rules vs Sudden Vector Projection Model" at https://pubs.acs.org/doi/10.1021/jp512021m .

•Cl + Cl- = •Cl2- (increases with chloride concentration)

•Cl + •Cl = Cl2 (kinetically not likely)

Cl2 + H2O = HCl + HOCl

Per a source (no access, see https://pubs.acs.org/doi/abs/10.1021/jp036211i ), pertinent rate constants are available, to quote:

"The rate constants for the reactions Cl•(aq) + Cl2-•(aq) → Cl2(aq) + Cl-(aq) and Cl2-•(aq) + Cl2-•(aq) → Cl2(aq) + 2Cl-(aq) are determined; rate constants for the latter are measured as a function of temperature and ionic strength."

Note, the •Cl2- radical is less reactive (than •Cl or •OH), but has greater longevity, and would be more of interest in contributing to the formation of aqueous Cl2 and therefrom HOCl.

So, yes a small amount of chlorine presence may actually be observed.

[Edited on 2-2-2022 by AJKOER]
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[*] posted on 2-2-2022 at 09:06


Quote: Originally posted by AJKOER  
As to the photochemistry here, it appears to be real (both Fe and Cu impurity in your bleach with light exposure is widely reported to speed decomposition, see discussion here http://www.sciencemadness.org/talk/viewthread.php?tid=158266)
OMG. Three posts of you talking to yourself is literally not a discussion. Just because you rambled about something for a while once doesn’t make it fact.

There need to be experiments that prove or disprove a hypothesis before you move on to the next one. That is how the scientific method works. You can’t just assume something works because someone else’s experiment A appears to support one half of your hypothesis, while unrelated experiment B appears to support the other half. Taking the conclusions from these experiments and saying that because hypotheses A and B are true, your new hypothesis C must be true, is fallacious reasoning. It’s post-hoc theorizing. I have no obligation to try and disprove any of your claims, because you never proved them to begin with! You’ve spent years theorizing and drawing conclusions from other people’s experiments and piling one on the other over and over again. Assumption after assumption. At this point I have no hope of you ever going back on any of it. You’re too entrenched in your own imaginary world. You’ve spent far too much time constructing it to question it now.




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[*] posted on 2-2-2022 at 13:23


Quote: Originally posted by Texium  
You’re too entrenched in your own imaginary world.


sums up the dude pretty well
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[*] posted on 2-2-2022 at 17:06


I still find the theory that his name is an anagram of "A JOKER" compelling.
Not sure who suggested that, but it sure stuck with me.

Do you think he thanked Texium for his first post because it makes the page look more like a discussion, rather than the (well deserved) scientific beat-down it really is?

Me: resisting the urge to post a pointless GIF of Joaquin Phoenix.




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AJKOER
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[*] posted on 2-2-2022 at 17:50


Texium thanks, I agree with your statement, but I am a bit obtuse of what hypothesis I have extolled.

For example, it is well known that the decomposition products associated with hypochlorite bleaches (mega dollar products marketed by said industry) have undoubtedly been extensively researched as to why their products have a limited shelf life. My citation of one such report appears somewhat factually suggesting that NaOCl bleach do, in fact, decompose with exposure to light especially in the presence of the either Fe or Cu ions. Currently, there is some literature relating to the amazing catalytic properties (better than TiO2 in select tests) of ferric chloride, however, much more limited (but some work) relating to cupric chloride photosensitive properties. My ‘feeble’ claim, given that the indicated decomposition products are NaCl and NaClO3, suggests to me, given my prior documented thread (see http://www.sciencemadness.org/talk/viewthread.php?tid=34429#... ) on this very forum of successful chlorate creation from a proposed radical path (which is pretty much still consistent with the current photolysis literature), that photo initiated radical based path are possible. So, an ascribed photosensitive compound, releasing electrons leading to radicals may be responsible for said associated chlorate formation. I have, in fact, demonstrated (per a review of the literature, in my pictures and even ignition testing) that such paths exist per my referenced thread. So my ‘feeble’ claim is more like, in my opinion, an obvious re-affirmation of the more recently associated photocatalytic properties surrounding ferric and cupric chloride.

If there is something else you have in mind, please let me know as I have carefully documented my reaction equations source and was carefully in my language using words like ‘possible’, ‘likely’, etc.


[Edited on 3-2-2022 by AJKOER]
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[*] posted on 3-2-2022 at 00:45


Quote: Originally posted by AJKOER  

For example, it is well known that the decomposition products associated with hypochlorite bleaches (mega dollar products marketed by said industry) have undoubtedly been extensively researched as to why their products have a limited shelf life. My citation of one such report appears somewhat factually suggesting that NaOCl bleach do, in fact, decompose with exposure to light especially in the presence of the either Fe or Cu ions. Currently, there is some literature relating to the amazing catalytic properties (better than TiO2 in select tests) of ferric chloride, however, much more limited (but some work) relating to cupric chloride photosensitive properties. My ‘feeble’ claim, given that the indicated decomposition products are NaCl and NaClO3,


[Edited on 3-2-2022 by AJKOER]

Decomposition of hypochlorite is, indeed,well documented.
https://cdnsciencepub.com/doi/pdf/10.1139/v56-068

Simplistically,
If you add cobalt (etc) as a catalyst you get salt and oxygen.

You can get disproportionation if you boil it.

No need for pointless speculation.
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AJKOER
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[*] posted on 3-2-2022 at 04:42


Thanks Unionised for that albeit dated (1956) research confirming products.

However, quite clearly that study does not examine the role of light in hypochlorite decomposition.

Further, more interesting, is no citation of the role of Fe, yes iron impurities, in that light free examination, as is attested to in my much more recent reference. While many are aware of so-called Fenton chemistry around Fe/Fe++ reacting with H2O2, there is apparently a faster corresponding reaction with HOCl, also resulting in radicals!

Note, my chlorate preparation thread focused on a light induced radical path, where the latter mechanism is now more currently listed (involving the .ClO radical and with HOCl) as a potential route to significance chlorate formation.

More curious, having cited on this forum (from a book on chemical hazards) the accidental chlorate explosion from boiling NaOCl in a pan coated with burnt vegetable in an effort to remove say carbon problem, having again forgot that it was on the stove, wherein a notable explosion occurred, does confirm that boiling hypochlorite in the presence of oxygen, suitable metal and carbon can possibly create and eventual detonate a chlorate. However, in my opinion, this path has little to nothing to due with the self reaction on boiling dilute aqueous NaOCl (which I would rate as a very weak path), more like steel/Fe acting on HOCl from vegetable acids (forming radicals) interacting with NaOCl, and possibly even the further presence of oxygen reacting with electrons from the Bleach battery cell from an anode of Fe and cathode of C, all again in my opinion).

[Edited on 3-2-2022 by AJKOER]
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[*] posted on 13-2-2022 at 09:28


Why not add freshly prepared Cu(OH)2? It does react with dilute HCl.

[Edited on 13-2-2022 by ave369]




Smells like ammonia....
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AJKOER
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[*] posted on 20-2-2022 at 20:03


Yes, Ave369, I agree!

This closely relates to my opening thread cited product from the reactions:

2 Cu + O2 + 2 H+ -> Cu2O + H2O (an electrochemical reaction)

Cu2O + 2 HCl -> 2 CuCl + H2O

which is more of a CuOH than a Cu(OH)2 neutralization path of the HCl starting with widely available copper metal.

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