. As the non-magnetic fraction obtained
from the first magnetic separation was subjected to a second
magnetic separation at 3000 Gauss, the cumulative recovery
of nickel–iron concentrate increased from 83% to 94% based on
the whole printed circuit boards, but the grade of the concentratedecreased considerably from 76% to 56%. Meanwhile, the cumulative
recovery of copper into the non-magnetic fraction decreased
from 92% to 76% due to more separation into the magnetic fraction,
as shown in Fig. 6. Despite this 16% loss of copper into the magnetic
fraction by the second magnetic separation, the grade of
the copper concentrate in the non-magnetic fraction increased
slightly to 75% as a result of the removal of other major metals into
the magnetic fraction