Making Copper Parts from Algaecide

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In this video I'm going to show an easy method to extract pure copper metal from copper sulfate and then I'll melt it down and use a homemade CNC mill to machine the castings into parts. In this case, the parts were just decorative, but you could absolutely use this approach to make useful parts too. I had lots of copper sulfate laying around because I like using it to grow crystals, but you may also have some on hand if you do gardening or pond maintenance.

Copper metal (Cu) can be extracted from copper sulfate (CuSO4-5H2O) by electrolysis, or by simply inserting a metal into the solution that's more reactive than copper (which is most metals). When this happens, a single-displacement reaction takes place, wherein the copper atom is dropped and the sulfate ion bonds to the other metal, leaving copper dust to precipitate out. The nice thing about dissolving metal this way is that there's no nasty fumes generated as in the case with strong acids or bases.

Copper sulfate pentahydrate is 25.4% copper metal by mass, and sells for around $2/lb in the US, so if you neglect the cost of the scrap metal, that comes out to $8/lb of copper metal, which isn't too far above the the cost of copper scrap at the time of publishing this video, which is $5-7/lb in the US. As a bonus, if you used electrolysis instead of dissolving scrap metal, you'd be left with sulfuric acid after extracting the copper, which is useful on its own.

The fine copper dust that precipitated out oxidized pretty quickly when I dried it, so in my first attempt to melt it, it just stayed oxidized and didn't liquify. When I mixed brazing flux powder in with the copper powder, I did succesfully manage to melt it. In total I chemically produced and melted a little over 1kg of copper for this project.

Parts were cut on my CNC mill with a 1/8" end mill traveling 8mm/sec with a 0.1mm cut depth, although i later reduced that to 0.05mm because the mill isn't rigid at all, so that's something I'll need to fix in the future. It works pretty well on aluminum and brass, but struggled quite a bit with copper.

Since both parts were decorative, I aged one of them by exposing it to Ammonia fumes for several days, causing deep blue copper hydroxide to form on the surface, which made it look like some sort of ancient artifact. I also experimented with fumes from Sulfuric Acid, Nitric Acid, Acetic Acid, and Hydrochloric Acid for aging, but I think Ammonia fumes gave the best appearance.

In most cases this probably isn't a very practical project, but I thought it was pretty interesting to go through the process of transforming a blue liquid into solid metal parts.

Music Used:

Kevin MacLeod - Lobby Time
Kevin MacLeod - Hard Boiled