I've once cut open a Britta filter and it had only charcoal mixed with pearlite (looked like 50/50 mix, 1-2mm gran.) and of course, a small magnet.... Britta filters have other things in them to further catch what the carbon cannot...
The point being that the magnetic field brakes the mineral molecules from the water and the charcoal/pearlite does the mechanical separation. The actual filtration.
It's the same filter I use for the water I cut the moonshine with, the poor man's RO machine. Redneck technology.