The clue to the idea of plating metals out is the same as to plate on, the solution needs to have metals in solution to start the process whether it's drawn from the metals you want to strip or in the solution to start with. There are plenty of patents for this out there but they all seem to leave some material in the solution that needs to be recovered. The sulphuric cell is excellent in that the gold is dissolved by the formation of per sulphuric acid and that only forms for a short period or distance when it becomes sulphuric again releasing the gold from solution. The bad thing is sulphuric especially concentrated sulphuric is about as nasty an acid as we deal with in refining, for the cell to work well the acid needs to be 95%+ and must not be run to hot or base metals will also start to dissolve in quantity. The other problems are is that the acid is very thick meaning settling takes time and using paper filters is a definite no no as the acid will destroy your filter unless the acid is well diluted. Read up the process of using the cell very carefully and fully understand the dangers associated with using concentrated sulphuric, this is nasty unforgiving acid.