What is the difference between hemodialysis and hemoperfusion?

Both of these procedures can be used for overdose/toxicity treatment in an emergency.

Hemodialysis is having blood pumped out of the body and equalize with a column filled with isoosmotic solution and electrolytes (think of it as a second kidney).

Hemopurfusion is pumping blood out of the body and running it through a column of activated charcol (which will bind to most poisons). This of this as giving activated charcol in a more rapid pace.