Re: Copper Sulfate production


"Overclocked" <Overclocked2300@xxxxxxxxx> wrote in message
news:1161656864.821076.12960@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Id like to use electrolysis because it outputs a large amount of
product with a minimal of reactants.

While comparing an amount of current to an amount of a reagent is not
possible, you might be surprised how much current is equivalent to how much
reagent. Say you want to make 150 g of CuSO4 (that's about 1 mole).
That'll require 1 mole of H2SO4, or about 100 mL, or it'll take 2 moles of
electrons. That's about 193,000 Coulombs, or 193,000 amp-seconds. That's
one amp (which is quite a high current for a small electrochemical cell) for
53 hours straight. That's quite a bit of electricity compared to about 1/2
cup of H2SO4. And that's assuming that the e-chem cell is 100 % efficient.
Plus, don't forget to run that e-chem cell, you'll need clean water, and a
very soluble electrolyte that won't react with the Cu(II) ions and interfere
with the crystallization of CuSO4. That leaves out hydroxide, chloride,
acetate, and some others. You need a very soluble electrolyte because you
want the solution be be conductive enough to easily carry all that current
without a huge overvoltage. You don't want the solution to be alkaline, or
you'll get hydrolysis to Cu(OH)2 and a gel containing various Cu(II) oxide
hydroxide species. Not conducive to good crystal growth. NaNO3, Na2SO4,
MgSO4 or H2SO4 might be good choices as the electrolyte. H2SO4 is probably
the best of these, since it is liquid, and won't crystallize out as you
evaporate the solution to concentrate the CuSO4 so it crystallizes. But now
you're getting into a realm where it might just be simpler to do the
reaction with conc. H2SO4 (battery-acid grade, which is about 10 % IIRC) and
be done with it. You're going to consume some H2SO4 in any case, as you
need the SO4= for the CuSO4.

Eric Lucas


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