Nickel coated paper clips do not react as
readily as uncoated iron paper clips with the copper in the
copper solution, so use non-coated paper clips or steel wool.
The precipitation of the copper metal
generally produces an orange precipitate on the iron paper
clip. The precipitate starts out black, and gradually takes
on an orange color as more copper precipitates. Occasionally,
nice copper crystals form. This normal orange color can be
mistaken for rust (hydrated iron (III) oxide). Observations
can show that this is not the material formed. A control in
which a paper clip is dropped into plain water does not
produce the orange precipitate as does the experimental
situation in which copper is present in solution. Notice that
the blue color of the copper sulfate solution disappears as
the amount of orange precipitate on the paper clip increases.
This means the copper is being removed from solution.
Washing the model heap for reclamation may
take prohibitively long. If so, continue with a discussion of
how the situation might be improved at an actual mine. First,
the ore would probably be nearly completely recovered, so
washing to remove residual ore metal would probably not be so
important. Trace metals might be a problem and require some
special treatment to immobilize or remove those metals.
Bacteria play an important part in preparing the heaps for
reclamation because bacteria have been used specifically to
remove problem metals from the system.
