There is a fair misconception about that the "blue stuff" or "green stuff" you see on mine walls is either copper carbonate/sulphate. The reality is that it's copper silicate which could be abbreviated to "silica with a bit of the above giving it it's colour".
I retrieved a bucket of copper (blue) flowstone and decided I was going to smelt it and make me some copper nuggets.
Upon putting it into a bucket, it became liquid like blue pancake mix. I dried it out on binliners before putting it in a pot in a bonfire. Rather than getting a load of red copper oxide, I got the silica with a reddish tinge. Think talcum powder with a bit of rust. Undeterred, I smelted it, using an industrial vacuum cleaner and a plantpot/bucket/coal furnace. I got a very small copper nugget and my estimation of the ore was that it was about 2% Cu.
Bedford united has good "green stuff" in a river but again, most of this is silica. The actual concentration of CuSO4 in minewater is very little, really very little. The secret is getting the superweak solution in contact with as much bare iron as possible, as the reaction happens 100% of the time, for sure. If you do it right, you can get a very high yield.
There was a precipitation works at bissoe, as well as the ever popular ochre recovery. I've pondered the dissolved metals in the county adit and wondered why nobody is using those ponds. It's almost like ignoring something to be recycled.
The catch is this. You get a sludge, in order to get a marketable product, you need to cast it into ingots. This is a pain and probably why nobody does it.
I've climbed down countless ladders and observed the copper encrustations on them. The water in one shaft is actually blue with what I can only imagine is copper sulphate. There must be dozens of kilos of the stuff in there.
Getting one of these right would involve a whole load of trialling, rather than theory.
The crux of the matter, for efficient copper production would be noting the rate of reaction. Different solutions/impurities would influence the porosity of the product. It's all very well chucking a load of scrap picks/hilts into a pond and leaving it for a decade and then digging the stuff out as a bonus, years later, the name of the game is getting the reaction to happen as thoroughly as possible, with as little copper sulphate solution going to waste as possible.
If I was to do it, I'd go for machine shop swarf as a starting material and then get the liquor to flow down a gutter about 6" deep, which would be filled with swarf, perhaps 30ft long or so. I'd then have a deep tank with a centre baffle at one end, as to force any sediment to drop out of solution. A couple of these set up in parallel would be ideal, so you could clean one out whilst running the other.
If you could have the rig set up so you could jack up one end and decant the supernatent liquid, it would give you your precipitate easily and quickly.
I'm not sure what the yield could potentially be, but it would most certainly be a few quid, for very little work. (assuming you designed and built it right).
S :thumbup: