In the purification of lead electrolytically,which of the following facts is not correct?

$\begin{array}{1 1}\text{Crude lead acts as anode}\\\text{Pure lead acts as cathode}\\\text{Electrolytic solution contains }PbSiF_6,H_2SiF_6\\\text{Anode mud contains copper only}\end{array}$

Answer : Anode mud contains copper only
Anode mud contains many other metals such as Ag,Au,Sn,As and Sb