unknown compounds of PCB etchants sold on aliexpress

[tuvtuv]

i feel quite embarrassed about it, but for last two years ive been making PCBs using a product sold on ali-express as "blue etchant" as it becomes blue after dissolving copper ions, and ive guessed all along that it is probably ammonium-persulfate  or sodium-persulfate.

then, after buying the same material several times over and over, ive bought another etchant called "blue green etchant" and like an idiot ive used it to strengthen the solution, and the result was chlorine gasses bubbling out making an unbearable smell, so ive put the solution in the balcony and left the house for few hours so it would ventilate.

now im stuck with two solution containers, one with the "blue" etchant and another with the "blue green" etchant + "blue" etchant (after they settled).

ive asked the chinese sellers about this materials and they say that they dont know!! so question is, what is the blue etchant and what is the blue green etchant? any guesses?

P.S.
ive learned my lesson not to buy chemicals on aliexpress, all i want is to get rid of the chemicals in a environment-friendly way... im thinking of using sodium bicarbonate to settle the acidity, and evaporate the solution to crystals, and then send it to a chemical dumpster somehow(university?), and if unavailable, put it in the trash.

[sleemanj]

I'm not a chemist, but I've assumed that the "blue" etchant is probably a persulfate and the green etchant (or blue green) I'd maybe guess as CuCl (which is a white powder vs CuCl2 which is blue), with perhaps percabonate for the extra 02, some powdered acid and some salt for extra Cl.

If you search taobao for: ok this forum doesn't like chinese characters so copy from this google translate link  (use Google Chrome so you can translate the pages) you will find some sellers which give more information (example - no affiliation, just one of the links found) but a quick look I couldn't see any that actually specified the ingredients.

I actually have a couple bags of this stuff around somewhere, I think it's this stuff, it was a free gift in an order.... which gives me the creeps having an order coming through customs with a bag of white powder in it that I didn't know was in it, and also, still have no idea what exactly it is.

Anyway, I'd neutralise your etchant, evaporate, and dump it in your bin, if your localities waste management is up to snuff it should be safe to do that.  HCl and H202 are available in most places, or online in most places, and are a pretty good etchant combination (outside, of course!!)

[tuvtuv]

thanks for the fast answer.

you have strengthened my belief that it is probably cucl.

for now, i sent the substances to the university so that a friend might try to dispose of it safely using the help of some chemistry lab. not sure how this will go, if it doesnt, i will neutralize the acidity, dry it in the sun, and dump the crystals in the bin

[Aodhan145]

thanks for the fast answer.

you have strengthened my belief that it is probably cucl.

for now, i sent the substances to the university so that a friend might try to dispose of it safely using the help of some chemistry lab. not sure how this will go, if it doesnt, i will neutralize the acidity, dry it in the sun, and dump the crystals in the bin

Disposing of it that way is probably what your meant to do. I just dilute my etchant in the toilet and flush it.

[free_electron]

Disposing of it that way is probably what your meant to do. I just dilute my etchant in the toilet and flush it.

sure, go pollute a bit with Coppersulphate ...

[Aodhan145]

Disposing of it that way is probably what your meant to do. I just dilute my etchant in the toilet and flush it.

sure, go pollute a bit with Coppersulphate ...

Copper sulphate would be bad as it is toxic. Copper Chloride is not that bad if really diluted and I am not a pcb fab company. I make around 1 pcb a month and re use the etchant which is only like 50ml of ferric chloride so I am not that bad.

[nctnico]

Copper is a heavy (toxic) metal which should not end up in the surface water because no matter how much you dillute it, it will be accumulated somewhere in nature (and end up in your food). So next time bring it to chemical waste disposal depot)!
BTW You can re-use Ferric/Copper Chloride forever. Just add a bit of HCl (hydrochloric acid) when etching starts to slow down.

[Aodhan145]

Copper is a heavy (toxic) metal which should not end up in the surface water because no matter how much you dillute it, it will be accumulated somewhere in nature (and end up in your food). So next time bring it to chemical waste disposal depot)!
BTW You can re-use Ferric/Copper Chloride forever. Just add a bit of HCl (hydrochloric acid) when etching starts to slow down.

Yeah that makes sense can you precipitate the copper chloride out after adding the HCL?

[Towger]

No worse then modern copper based antifouling used on boats. If you scrape a load of old stuff off over grass, it kills it for a couple of years.

[Siwastaja]

Copper is a heavy (toxic) metal which should not end up in the surface water because no matter how much you dillute it, it will be accumulated somewhere in nature (and end up in your food).

    

Sure, in huge amounts, copper is problematic in nature, food and body.

On the other hand, copper is necessary for life. The vitamin supplement I'm taking right now while writing this gives me 0.5 mg, which is 50% of the daily intake value (EU). Why is this added in this multivitamin product? Because some research has probably shown that many food products don't have enough.

We literally eat copper, and we would literally die without it. You probably urinate copper down the drain during a few years more than what the OP is going to dispose of, so stop urinating first before blaming others.

Copper's everywhere in the nature, and life would end without it. It's not comparable to elements usually called "toxic heavy metals", which are not only unnecessary but very toxic (many orders of magnitude more than copper): lead, mercury, cadmium...

But yes, copper is kind like sodium (table salt) in your system, and in ecosystem, too; it has to be in balance. That's why wasting is controlled, and large companies producing a lot of copper waste must be very careful with it. A PCB hobbyist getting rid of an etchant? Not a problem. This is similar to a traditional photography hobbyist getting rid of used fixer solution, releasing a bit of silver. At a commercial level, at times when all photography was film-based, that would have been a problem if it was unregulated.

There are elements that are really toxic in nature, even in small amounts, so that no wasting can be allowed, even on hobbyist level. Copper is not one of them.

Any questions?

[sleemanj]

A PCB hobbyist getting rid of an etchant?

Is not getting rid of copper metal but copper salts depending on etching chemistry.  There is a difference  between dropping a chunk of copper in a river, and pouring a pile of cupric chloride into your water table.

"The most bioactive and  toxic form of the copper is cupric ion Cu⁺².  Aquatic life is 10–100 times more sensitive to
the hazardous effects of copper than mammals." 

[NiHaoMike]

I remember reading that copper based chemicals are sometimes used to prevent tree roots from growing into (presumably leaky) drain pipes.

[Siwastaja]

A PCB hobbyist getting rid of an etchant?

Is not getting rid of copper metal but copper salts depending on etching chemistry.  There is a difference  between dropping a chunk of copper in a river, and pouring a pile of cupric chloride into your water table.

"The most bioactive and  toxic form of the copper is cupric ion Cu⁺².  Aquatic life is 10–100 times more sensitive to
the hazardous effects of copper than mammals."

Of course it's in ionic form. That's exactly what I'm talking about when I talked about copper in environment on the previous reply. Copper as a metal is several orders of magnitude less problematic. Etchant solution has copper in its ionic (dissolved) form, but so has the multivitamin pill, or it wouldn't work.

[rs20]

Copper sulphate would be bad as it is toxic. Copper Chloride is not that bad if really diluted and I am not a pcb fab company. I make around 1 pcb a month and re use the etchant which is only like 50ml of ferric chloride so I am not that bad.

What? Copper is copper, it doesn't matter what the anion floating around in the same solution is.

You probably urinate copper down the drain during a few years more than what the OP is going to dispose of, so stop urinating first before blaming others.

False. You have a problem if you excrete more than 60mcg/day, which works out to 1.5 grams per 70 years. That's a fraction of a single etchant bath, over a lifetime. It's true that in any given large city's waste water system, one etchant bath is not going to make much of a difference though. Interesting to speculate where the Cu content ultimately ends up?

[Psi]

BTW You can re-use Ferric Chloride forever. Just add a bit of HCl (hydrochloric acid) when etching starts to slow down.

It must get saturated with copper eventually. If your only diluting it a little with some HCL the copper has to accumulate somewhere?

[Ian.M]

Acid Cupric Chloride is itself an etchant. Just bubble air through it till the solution is regenerated.  See: http://techref.massmind.org/techref/pcb/etch/CuCl2.htm
It also has some suggestions for safe disposal.

[chickenHeadKnob]

Nurd rage the youtube inorganic chemist has a few videos on making your own etchants and recycling them.

Recover Copper from Ferric Chloride Etchant (Waste free method)  https://youtu.be/CY2T3orVuFU
Recycle Copper chloride PCB etchant (waste free method)               https://youtu.be/FjEoRidvgYE
Make Copper Chloride (3 ways)                                     https://youtu.be/V8mHiFYmlBc
Make 10 Etchants for Copper Printed Circuit Boards    https://youtu.be/Q4tWEse2rDI

[nctnico]

Copper is a heavy (toxic) metal which should not end up in the surface water because no matter how much you dillute it, it will be accumulated somewhere in nature (and end up in your food). So next time bring it to chemical waste disposal depot)!
BTW You can re-use Ferric/Copper Chloride forever. Just add a bit of HCl (hydrochloric acid) when etching starts to slow down.

Yeah that makes sense can you precipitate the copper chloride out after adding the HCL?

You don't need to get rid of the copper chloride; that is the beauty of this method. You can etch with copper chloride as long as it is kept activated which is where the HCl comes in. A similar process was/is used in PCB factories but in those they add Chlorine to reactivate and other chemicals to split the excess copper from the etchant. However for a few boards per year evaporation gets rid of excess liquid. In my previous etching setup I have used the same etchant (Initially ferric chloride) for at least 20 years.

I can recommend everybody to read about the chemistry behind the various etching methods. It can be very enlightening. I have a book called 'designing and creating printed circuit boards' by 'Walter Sikonowiz'. My copy is from the 9th print in 1989.