RogueRose
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Oxidation via bubblers - what rate can be expected and how to improve absorption?
I'm trying to see how much O2 is produced via an air bubbler using 1CFM as a starting point for volume.
Oxygen: 20.99%
22.4 liters (@ STP) = 1 mole
1 ft^3 = 28.32L
1 ft^3 = 1.26414494 mole
Per cubic Ft
Oxygen (O2): 0.2653 moles
Weight of element per cubic foot
Oxygen: 8.49g
1 hour @ 1 CFM
509.4g of Oxygen
24 hrs @ 1 CFM
12,226g of Oxygen
The problem is, after running at 2CFM for 36 hours (36.678 KG or about 81lbs of Oxygen), I thought I would have complete oxidation but it seems it has
done little to oxidize the Cu in a 31% H2SO4 solution. I've tried 35% H2O2 and about 16oz seems to be about what I would have gotten from the 36
hours.
The bubbler is a sealed PVC pipe with 4 1mm holes and the air exits in tiny bubbles - IDK how to make the bubbles absorb better.
Also with H2O2, since it decomps to: 2H2O2 -> 2H2O + O2 for every 2 molecule H2O2, one O2 is produced so a 35% solution only can produce 17.5%
pure O2 (actually less due to weight).
Can anyone give advice on how to make this work better?
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DraconicAcid
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If you want to oxidize copper, you want to use hydrochloric acid. In high concentrations of chloride, copper(I) salts are solubilized, and catalyze
the oxidation.
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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Copper reduces H2SO4.
Not sure on what you are trying to accomplish, but if just trying to put copper into solution, try 5% vinegar and dilute H2O2 with a touch of sea
salt. Jump start the reaction in a microwave for 30 seconds. For some background on the chemistry, together with pictures, please see https://www.sciencemadness.org/whisper/viewthread.php?tid=64...
One can replace the inexpense dilute H2O2 (that will be needed to replenish the copper acetate formation reaction) with an air pump, but after energy
cost, not sure if it really makes sense.
To make CuSO4, add NaHCO3 (baking soda) to the copper acetate and collect the copper carbonate precipitate. Treat with H2SO4 or NaHSO4 (then freeze
out the unwanted Na2SO4).
----------------------
Acid Free Paths
Heat the copper acetate to decompose (outdoors) leaving fine reactive copper metal. Dissolve the Cu in dilute ammonia + 3% H2O2 + touch of sea salt.
Caution: In the first 10 minutes, a significant nitrogen gas release will occur, from a decomposition of a side reaction creating poisonous NH4NO2.
So, no closed vessels and have a bowl under the reaction vessel to capture expected spillage.
When after further additions of NH3/H2O2, and all the copper has dissolved, add MgSO4, and let white Mg(OH)2 settle out. Continue to add the Epsom
salt until a white precipitate is no longer formed. Pour off the royal blue solution and boil to release ammonia leaving aqueous CuSO4 (not tested
this last part).
Electrolysis: apply a copper and an inert electrode (with, for example, carbon, but due to its physical breakdown during electrolysis, I have to
surround it with filter paper) to a solution of MgSO4. White precipitate of Mg(OH)2 is agained formed. With time, the solution becomes more intensely
blue as the concentration of CuSO4 increases.
[Edited on 24-9-2016 by AJKOER]
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RogueRose
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Wow, thanks for the suggestions on CuSO4 production! I had been making some with standard battery acid and H2O2 and it seemed to work pretty well.
When the H2O2 was poured on the Cu wire coils, it bubbled and produced steam and some coating on the copper (a tannish color, not brown like oxide,
but tan..) - then when dipped in the acid it bubbled/boiled furiously resulting in dark blue solution. If the H2O2 was poured in the H2SO4 & not
the copper, bubbles were produced when the copper coils were stirred in the solution and very fine bubbles were produced. This happened until, what
seemed to be, the H2O2 was used up. This method seemed to work well but it did seem to give off some "sharp" sulfurous vapors (SO2?) I'm guessing
that is the reduction that was spoken about?
So, I was trying to replicate the above but by using a bubbler instead to see how well it worked. There are a number of things I want to try to
oxidize using a bubbler like changing a nitrite/nitrate mixture into a nitrate solution.
I'm going to try a fabric diffuser on either side of a piece of PVC pipe to hopefully allow much smaller air bubbles to saturate the solutions.
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RogueRose
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Quote: Originally posted by DraconicAcid  | | If you want to oxidize copper, you want to use hydrochloric acid. In high concentrations of chloride, copper(I) salts are solubilized, and catalyze
the oxidation. |
Out of curiousity, are you saying HCl will oxidize copper alone or with a bubbler? I had originally read that CuCl2 (or is it CuCl??) could be made
by HCl alone & I tried this with 31.45% and got a little Cu in solution but it stopped fairly quickly (maybe 1-2g dissolved in 800ml HCl). Later
I read Cu is unreactive with HCl which was a shock to me as I made the "green acid" (33g Cu & 800ml 31% HCl mix) solution by mixing. I later
read that CuO needed to be mixed with HCl to make a Cu chloride.. So much conflicting info for amateur chemists.
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AJKOER
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With respect to bubblers, in the world of oxygen-alkaline bleaching as applied to wood pulp, I recall reading about a fine spray bubbler invented to
infuse the O2 to effect bleaching.
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wg48
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| Quote: Originally posted by RogueRose |
snip
The bubbler is a sealed PVC pipe with 4 1mm holes and the air exits in tiny bubbles - IDK how to make the bubbles absorb better.
snip
Can anyone give advice on how to make this work better? |
I thought it worked best with hydrochloric acid due to the formation of an oxychloride. I have tried in an open bucket but its very slow, weeks. I
used scrap copper wire flooded with 25% HCl and stirred it at least once a day. I did notice that wires that protruded from the solution where
attacked relatively quickly at the surface of the liquid.
I assumed the limitation was the low solubility of oxygen in water its only about 0.5% relative to air. So ideally you want a column packed with
copper wire or turnings with acid recirculation from the top but not flooding it and the air pumped in at the bottom flowing up similar to a packed
fractioning column. I never tried that because of concerns about the evaporation of the acid.
From memory the approximately 1mm Wires protruding from the acid dissolved completely at the air/acid interface in a day or two. Temperature probably
at 70F to 100F. So hopefully a column would at least reproduce that rate of dissolving the copper packing at about 0.25mm/day.
Did your air bubble thru the copper and acid or just the acid with the copper at the bottom of the container ? The chloride ions may be important to
form the oxychloride so you could try catalytic amounts of HCl in your sulphuric acid.
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Maroboduus
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How about just boiling the copper in strong sulphuric acid in a well ventilated environment? Or catching the SO2 and putting it to some other use?
You'll need twice the acid, but it's the fast way up the hill, and with pure copper and H2SO4 you'll get a clean product.
As for the bubbler, are you using 1CFM in your calculations because you measured that gas output, or because it's the rating of the pump? You might
need more of those 1mm holes to allow the pump to give its full output potential.
I'd also suggest a fiberglass cloth for diffusing air from your pump. It'll stand up to the acid and can be found at most hardware stores where they
sell it for making fiberglass patches and repairs.
EDIT: But W48's column Idea actually sounds like it has real potential. With an acid proof pump that would be a pretty cool setup.
[Edited on 24-9-2016 by Maroboduus]
[Edited on 24-9-2016 by Maroboduus]
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DraconicAcid
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No, it works best with hydrochloric acid because once you get some copper reacting (due to the oxygen dissolved in the acid), you get soluble
dichlorocuprate(I) ions. These can migrate to the surface of the solution and react directly with atmospheric oxygen to give copper(II) ions. These
migrate back to the surface of the metal to give more dichlorocuprate(I) ions.
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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RogueRose
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I re-worked my bubbler by making a diffuser. I took 3" PVC pipe and cut at about a 30 degree angle on each side so it looks like a pyramid (30 degree
on the inside of the pyramid so it has a larger cut opening). So instead of a 3" diameter/area it is closer to 4" circle area on each side. I then
epoxied some polyester like fabric on the openings and put a 1/4" hose adapter on it. It works great and make like a cloud of bubbles or like a mist
in the water.
I'm also guessing that heat would help this but IDK what to use as a heat source. I would think that 50-100w would be enough but with the acid I
can't use aluminum. I thought of using parts from a 1 cup coffee maker but they are aluminum it seems. An immersion heater might be possible (120 w)
but I'd have to order them. Does any one know of something that is liquid safe that would work?
I moved the bath over to a 135w crock pot and I figured this would work well but I can't use the bubbler with it as it would melt.
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unionised
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If you blow air through a solution of HCl everything in the room will go rusty unless you trap the HCl vapour/spray.
Lots of small bubbles will do a better job of dissolving air into the acid.
However the rate of reaction between dissolved oxygen and copper is still finite.
Increasing the surface area of the copper will help a lot.
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RogueRose
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Nylon hose bard disappeared in acid solution
I had a nylon hose barb connected to a bubbler in a 15-17% solution H2SO4 with copper wire in it. I pulled the bubbler out and the barb had
completely disappeared and was no where to be found. It seems nylon is not the best choice for acid use, especially HCl.
I am wondering what the nylon would have tunred into as it dissolved and how it may have contaminated the CuSO4. Can it be removed with filtering and
recrystalizations? Any suggestions on how to clean this?
I need to install some hose barbs on some bubblers but I need them to be chemically resistant to most acids and bases and possible some polar
solvents. What would be the best material for this. I'm thinking some kind of SS or possibly PTFE but I think a PTFE barb may me difficult to find.
I just need some 1/4" barbs, nothing huge.
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Texium
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Threads Merged
25-9-2016 at 08:20 |
Fulmen
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What is your end goal? If it's copper salts another process can be utilized. Ammonium carbonate and ammonia will leach copper using atmospheric oxygen
as an oxidizer.
We're not banging rocks together here. We know how to put a man back together.
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wg48
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Here is a pic of copper wire (coax shielding) in 15% HCl (estimated) Its about two days old. The lid was removed and swirled several times.
The copper initially was covered in oxide. When 22% HCl was added it produced a cloudy brown solution which settled to a light brown precipitate with
a straw colored solution.
When distilled water was added a white precipitate formed.
The solution is now a dark brown with I believe more white precipitate.
I believe the precipitate is Cu(I) chloride (not the oxychloride) and the solution a Cu Cl complex. Presumable if I remove the copper metal it will
eventually go green/blue as the Cu(I) is oxidised to Cu(II) by air and any remaining acid.
[Edited on 26-9-2016 by wg48]
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RogueRose
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Well I found that the H2O2 added to the HCl gives a very vigorous reaction and it seems the copper acts as a catalyst to decompose the peroxide (may
need an acid coating to initiate this..?). It is very similar to the sulfuric acid peroxide reaction with copper.
I had some magnet wire that had been burnt and I put it in the HCl to clean it. After soaking for a minute or two it was nice and shiny. I rinsed in
a bowl of water and allowed to soak. By accident I was dumping a solution of baking soda in the sink and the solution got in the rinsing bowl. The
water had been pretty clear with some black residue from the rinsing. The baking soda turned the water yellow/green and then eventually to a redish
brown and the wire was coated with this fine powder. I would have to guess it is Cu2O or maybe CuCl2 or a mix. It was definitely red but there was
some brown too?
IN the dish that had the HCl/H2O2 mix, when it cooled there were crystals on the bottom that were white/tanish with black powder settled on it. It
seemed to flash H2O2 to steam when it was added. I'll try to get pic of this later.
What I am trying to do is create a number of copper substances such as the 2 chlorides, oxides, hydroxides, sulphates, nitrate, amine's (and
complexes) and copper powder/dust. If there are other interesting salts/compounds that can be made I would like to hear about them.
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wg48
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I wondered if the sulfuric acid, copper and air method produces Cu(I) sulphate. Apparently almost none as Cu(I) sulphate disproportionates to Cu(II)
sulphate and copper.
From: http://copper.atomistry.com/cuprous_sulphate.html
"Cuprous sulphate, Cu2SO4, cannot be isolated by methods analogous to those employed for the preparation of the cuprous halides. Metallic copper
dissolves in solutions of cupric sulphate containing free sulphuric acid, an equilibrium corresponding with the scheme
2Cu•⇔ Cu•• + Cu
being attained. At ordinary temperatures the proportion of cuprous sulphate formed is small, but it is increased by rise of temperature."
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wg48
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The copper in dilute HCl is now > two weeks old. More copper has been added so some is above the solution. It has been stirred and exposed to fresh
air at least one a day.
The exposed copper develops bright green covering (presumable the oxy chloride) which dissolves when covered by the solution. the solution surface
was clear.
Today the exposed copper and the solution surface was covered by the green compound. Perhaps the HCl concentration has decreased sufficiently to
allow this to happen at the solution surface. There is also some green precipitate at the bottom above the whitish precipitate (CuCl). I was
beginning to think it was never going to go green.
Sorry the color balance and general quality is poor my spot light died.
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