Which method is used to obtain pure nickel from impure nickel?

In electrorefining of metals,the anode and cathode are taken as a thick slab of impure metal and a strip of pure metal,respectively,while the electrolyte is a solution of a complex metal salt. This method cannot be applied for the refining of:

Name the common elements present in the anode mud in electrolytic refining of copper. Why are they so present?

Which element is obtained in the pure form by the Van Arkel method?

Match the following:

List-$I$ (Process)	List-$II$ (Metal)
$A$. Hall-Heroult process	$I$. $Ti$
$B$. Mond process	$II$. $In$
$C$. van-Arkel process	$III$. $Al$
$D$. Zone refining process	$IV$. $Ni$

The correct answer is:

Silver can be separated from lead by