Recycle Copper chloride PCB etchant (waste free method)

Recycle Copper chloride PCB etchant (waste free method)


WARNING: This experiment handles boiling hydrochloric acid and sulfuric acid as well as toxic quantities of ionic copper. Gloves should be worn and the experiment should be performed outside or in a fume hood. Greetings fellow nerds. A popular printed circuit board etchant is copper chloride in hydrochloric acid. Its main advantage is that it’s easily regenerated by adding additional hydrochloric acid and bubbling air through it, creating more etchant the more you use it. However eventually you’ll have far more than you’ll need. In this video we’re going to fully recycle the etchant and recover the hydrochloric acid and copper that went into it. As an added challenge, we’re going to try and do this without creating any other chemical waste at the end. Let’s get started. Here is the copper chloride etchant solution already transferred to this flask. We first need to recover the hydrochloric acid so we’re going to set up our distillation apparatus. Once that’s ready, turn on the stirring, the water supply and finally the heating. No before you start it’s a good idea to filter the etchant to remove any insoluble particles. Also, if you have a very high acid concentration, greater than 20% by mass, you need to dilute the etchant so it’s lower than 20% before you distill. This is so that during distillation you don’t release hydrogen chloride gas first and waste it to the environment. If this doesn’t bother you and you’re just after the copper, then you can distill straight away. If you have a very high concentration, but are unsure of much you need to dilute it by, then adding an equal volume of water is usually enough as this brings most commercial concentrations of hydrochloric acid to below 20%. You can then discard the excess water during distillation as the water will distill off first. Similar to how we distilled sulfuric acid, you can tell when the distillation starts distilling acid by watching the receiver. If you see the distortions of the drops sinking then you’re distilling hydrochloric acid and you should change out the receiver to collect it. At this point distill all the way until the residue is dry. And here is our dried residue of copper chloride. It has this non-uniform appearance because there is a mixture of copper (II) chloride and copper (I) chloride present as well as various amounts of residual water and hydrochloric acid. Okay, we can go to the next step with just this amount. But since i have a lot more copper chloride etchant I need to recycle i’m going to distill the rest of this and collect all the copper chloride to do it all at once. I’ll skip over the remaining etchant since it’s just a repeat of what you saw earlier. Here we are with all the combined dry copper chloride and hydrochloric acid. Weigh the copper chloride so we know how much of the chemicals we need in the next step. I have around 20 g. For every gram of copper chloride measure out 7 mL of water and 1 mL of sulfuric acid. Okay, now we need to convert the copper chloride into copper sulfate in order to recover the copper. Since we have around 20 g of copper chloride, we’ll be needing 140 mL of water and 20 mL of sulfuric acid at 98% concentration. Mix them up in an erlenmeyer flask for distillation starting with the copper chloride. Then add the water, and add the sulfuric acid last. Shake up the mixture to dissolve as much of of the copper chloride as you can. Now as you mix it, most of the copper chloride will dissolve into a green solution but occasionally there may be this white precipitate of copper (I) chloride. In concentrated hydrochloric acid both copper (II) and copper (I) chloride are soluble but since we removed all the hydrochloric acid by distillation and then added water only the copper (II) chloride is soluble and this copper (I) chloride is precipitating out. If this is present then we’ll need to oxidize it into copper (II) ions before proceeding further. To do this is very easy, we just get an aquarium pump and bubble air through it. This can take a very long time, up to a few days. Since i’m rather impatient i’m going to speed things up by stirring the solution on my hotplate stirrer as well as heating the solution to 60 degrees Celsius. This should be done in a few hours. What’s happening at this point is that we’re oxidizing the insoluble copper (I) chloride into soluble copper (II) ions. Anyway, here we are about three hours later with everything dissolved. Take out the air tube. And here is our solution containing a mixture of copper chloride, sulfates and sulfuric acid. Now we put it back on distillation, and distill off hydrochloric acid. Keep going until the residue is pretty much dry. What we’re doing here is converting the copper chloride into copper sulfate. The removal of hydrochloric acid drives the equilibrium to the right. Now if you calculated the stoichiometry you’ll find we used an excess of sulfuric acid. This is to ensure we drive off all the hydrochloric acid and ensure we have negligible chloride contamination in our copper sulfate for the next step. Okay, we are done when we see this misting happen in the flask. This occurs when almost all the water is driven off and now the sulfuric acid is starting to vaporise. At this point, turn off heating and let it cool completely. Now we have our copper sulfate. It’s this very light color because we’ve driven off most of the water. Now we need to add some water back in. For every mL of sulfuric acid we used, we add at least 4 mL of water. Since we used 20 mL of sulfuric acid, we now add 80 mL of water. You can add more if you want. Now thoroughly mix the solution to dissolve the copper sulfate. Here we get the famous deep blue color of copper sulfate. Not all of it will dissolve but that’s acceptable for the next step. Transfer the mixture to a beaker including the undissolved copper sulfate. Now we electrolyze the solution. First fashion a copper cathode. I’m using some copper wire. And partially bury it in the copper sulfate at the bottom. Now just above that hang a platinum anode. I’m using a platinum coated titanium anode. Make sure they don’t touch.
Attach a constant current power supply with the negative terminal connected to the cathode and the positive terminal connected to the anode. Run the electrolysis with a current density of under 100 ma per square centimeter of exposed platinum. This will take a very long time so be patient. What we’re doing here is plating out the copper ions onto the cathode to get copper metal. At the anode, we’re electrolyzing water to get oxygen. The sulfate remains in solution and we get sulfuric acid. We’re essentially recovering copper metal and sulfuric acid in this step. The undissolved copper sulfate will dissolve as the concentration in solution decreases from the copper metal plating. That’s why we didn’t need to completely dissolve the copper sulfate before we started. We’re using a platinum anode as it’s one of the few anodes that can withstand this sort of electrolysis. You can also use a lead dioxide anode if you happen to have one. We couldn’t electrolyze the copper chloride because the anode would release chlorine gas and waste the hydrochloric acid, not to mention that chlorine is also toxic. That’s why we went through the trouble of converting it to copper sulfate. Now in my particular run, I had to electrolyze for about four days so i’m going to skip ahead. I also had to stir the solution on the second day since the copper sulfate wasn’t dissolving fast enough. But anyway, here we are four days later after the solution has gone completely clear. Lifting out the electrodes we can see the copper wire is much thicker than it was originally. This is due to the copper plating out onto it. An interesting point is that this copper is essentially the copper that originally came off the printed circuit board during etching. It all ended up here. The brown powder in the beaker is actually copper metal that fell off the cathode. You can filter it off and recover it. The solution is sulfuric acid and water. You can purify it by distillation as shown in a previous video or use it in future electrolysis runs. Anyway, there you have it. From a batch of spent copper chloride etchant we have recovered all of the hydrochloric acid by two distillations. And we have recovered all the copper by electrolysis. We used sulfuric acid as a catalyst and completely recovered that as well. We have fully recycled the etchant back into the starting materials without producing any chemical waste. Thanks for watching.

100 Comments

  1. @NurdRage  Your videos are absolutely awesome (watching them for years now)

    You can totally make any video you like, but just as a suggestion, please try something other than etching related stuff
    I miss the old NurdRage 🙂

  2. After looking back on some previous videos, would you also be able to add in H2O2 to oxidize the copper(1), without causing contamination?

  3. This might be a silly question, but why does the copper not react with the H2SO4 in the beaker containing the final products?

  4. i have bought cuso4 from the local store but it is contaminated with insoluble particles what should i do to get nearly pure cuso4 ?

  5. i would like to see you work with periodic videos on some kind of experiment at some point.  that would be really interesting!

  6. That's really cool. I've gone down the route of "disposing" of spent etchant by reacting with sodium carbonate to precipitate copper carbonate, then filtering, drying and heating that to a few hundred degrees to produce copper oxide which can then be mixed with HCl to restart future etchant baths. That's nowhere near as clean as this process!
    Though my first step should be to fix the foaming problem with my CuCl etch bath, which worsens when the HCl concentration is increased (to speed etching). I suspect it's been contaminated with something, possibly from the cement cleaner I originally used as a HCl source.

  7. is there any chance that after the electrolysis end, the copper will react with the sulfuric acid solution?

  8. I am happy to see that your videos are back on YouTube.  We missed you while you were away.  I believe that your presentation may spark an interest in chemistry with some people.  And who knows?  Maybe one of them will go on to become a chemical engineer thanks to you.
    Keep it up please.  On with the Great Work…
    – — – Nikolai

  9. Hey there, would a graphite or manganese dioxide coated graphite electrode work? I think it might withstand the electrolysis and even if it flakes off during the process, it would be an interesting alternative to platinum since its much cheaper and easy to get.

  10. I'm a Chef and have no real idea what  is going on in your videos, but i enjoy them none the less… But i'm learning something by watching them.

  11. Since the procedure requires two distillation steps, as well as dealing with copper(I) chloride (all steps which require time and energy), wouldn't it be more economical to simply waste the hydrochloric acid and recycle only the copper, since that is the expensive part of the etching solution?

  12. Another great video. I was wondering if you know how to make Aerogel (and if so could you do a video or with it. It has some cool science to it)

  13. Sir, where would you recommend shopping for the tools and containers you most often use in these videos?

    I'm a newb on a budget…

    Thanks!

  14. If you increased the surface area of your platinum coated titanium anode, you could have run a higher current density, thus reduced plate out time, downside is the anode cost, but probably worth the investment. I've toured 2 board houses, National Tech and ECT, not certain what their processes are, except I do know its all in house and waste free, so could be similar if not identical.

  15. Hey guys, I'm a chemistry student and I have started a new chemistry channel, because I really enjoy showing and explaining easy and advanced syntheses or experiments.

  16. First reaction Oh no, I don't really feel like watching 8 minutes of this. I already lined up a whole list, and… oh, why not. Just see if I'll change my mind.
    20 seconds later This shit is interesting…
    8 minutes 16 seconds later Wait, the video's already over? But I need more homework!

  17. Love your videos!
    But when you electrolize your copper solution into metal you should avoid contact with air or you will slow the process by oxidizing the metal with air, the acid attacking the CuO and again current to convert the Cu(II) back to Cu metal. Besides in electrolysis you just set the voltage, if you set the current output either you do nothing or slow your process. This is one rare case where electric current finds itself a solution to your problem, don't correct it!

  18. I love your videos! Why didn't you just stop with the 20g of copper chloride? Just for science? Recovering some grams of copper does not seem worth the effort to me, if you pay for it with a lot of electricity. AND some copper chloride is always useful.

  19. Is this scalable? In other words, would it be possible to do this on an industrial scale and have the kilowatt hours of energy needed to make the reactions go to completion be reasonably cheap enough to get a return greater than breaking even?

  20. Hello
    I need your help it's possible to make copper nitrate from copper sulfate with nitric acid?

  21. Will the concentration effect of preferentially discharging chloride ions be eliminated if the copper (II) chloride solution is diluted to a rather low concentration?

  22. You need to update the ferric chloride etchant annotation. It still says "still working on this one, will be available in a couple of weeks" when the video is there. Just a reminder…

  23. I did the electrolysis by myself to regain copper metal. It just looked like in your video: The copper fell off the electrode and broke into many particles. How can you avoid that? I want the copper to stick to the electrode. Like in electroplating.. exactly this method is used, right? Why does it work out there?

  24. Is it possible to recycling the iron chloride along with the copper chloride and separate it? because in electronics i use this for the PCB.

  25. Would it be possible to convert the Copper(I) Chloride to Copper(II) Chloride before adding the sulfuric acid by bubbling water through the CuCl +H2O solution if more copper and HCL was added?

  26. It would be cool if there were a channel that could turn these chemical experiments into chemical process design videos on a small scale. Would be neat to see these steps scaled up in a process plant design. I like how nothing is wasted!

  27. Instead of bubbling the solution, couldn't you simply add hydrogen peroxide to oxidise it? Or would that not work?

  28. +Nurdrage What If you had a solution of sulfuric acid below 98% concentration, how would you calculate the stoichiometric amount of militers of sulfuric acid needed to convert all the copper(II) chloride into copper sulfate? Also have done the stoichiometry with anhydrous copper(II) chloride or with copper(II) chloride dihydrate?

  29. 2:39 If you have battery acid, you can use 6ml of water and 3ml of battery acid for every gram of copper chloride.

  30. Next step. Recover the oxygen from the electrolysis to oxidize the copper I chloride from a different batch.

  31. I'm mainly interested in the recovery of HCl from spent solutions. Could this process be adapted to also work with solutions of tin chloride and iron chloride?

  32. When I dissolve (using electrolysis) gold plated computer pins I end up with a solution containing copper sulfate and nickel sulfate. I have no problem plating out the copper, but what happens to the nickel sulfate that is in the solution? Does it plate out with the copper, or is it left behind in the solution?

  33. First etch using a solution of copper sulphate and sulphuric acid. PCB for etching as anode, copper electrode as cathode. This is a fast and waste-free one-step method. When copper starts vanishing, switch to an electro-less method eg Copper Sulphate and HCL so that current densities don't concentrate near tracks thereby thinning them. This way, 90+% of the copper is immediately recovered and no chemicals are consumed in the firs step.

    You may use this process to plate-up another PCB as your cathode which you may use later for high current applications.

  34. as I Google for HCl boiling point, I see numbers around 100C. in your video there's a fairly clear transition from first just getting water and then getting HCl (at what concentration?) can you speak to why this happens that way without needing to fractionally distill?
    thanks for the videos!

  35. I was looking for this! I saw this video when was released and finally I need this solution ! Thanks NurdRage i really admire your work

  36. what if you don't want to recover it but dispose of it safely, what is the best way to neutralize it and throw it out, about half a gallon ?

  37. I've got a problem with my first distilation… my hot plate will only take the solution to ~125 degrees and it's still not boiling… I've put this down to the concentration of copper chloride in the solution but it still seems to be a very high temperature to still not give me much boiling????

  38. You are saying that you could not electrolyze the etchant because you would produce chlorine gas.
    One question:
    I was always wondering, if you could just do that, collect the chlorine gas and bubble it back through the solution to oxidize the copper(I) back to copper(II). Of course just extract so much copper until you do not have any copper (I) left, then stop and start etching again.
    Would that technically be possible ?

  39. Is it possible to do this with brass (zinc and copper)? I'm fairly certain I could etch it the same way, but is there any way to separate the zinc and the copper in the final step?

  40. I just re-watched this. Awesome and very informative! I'm about to start etching my own PCBs and I want to have this option available. 😀

  41. Nice video. Can I use this method also for dirty solution of CuCl2 ? Platinum electrode is very expensive, is there some alternative metal?

  42. Let's try using sodium carbonate instead of sulfuric acid, it is less dangerous than sulfuric acid, we can get basic copper carbonate. firing it in a thick graphite crucible with blowing air and we'll get copper. You should do this if you have graphite crucibles lying around.

  43. Yeah but all the time and effort not to mention the carbon footprint do it it, surely it would be just as easy to just buy some more !

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