The Vis Purifier is a thaumic device researched from the tainted knowledge section in Thaumcraft 2. Its basic function is to remove taint from the player's devices leaving behind only pure Vis.
When attached to any device that distributes/receives Vis via the holes on either end of it, this powerful machine will separate the taint from the Vis leaving the player with pure Vis. Like the Vis Filter this device does release taint into the air. However, unlike the Vis filter this device destroys some of the passing taint releasing significantly less into the air than a system of Vis filters.
Hooking up an open flow of vis/taint to somewhere between 4 - 8 purifiers which are hooked into each other appears to have a great chance of destroying most if not all free roaming taint in the player's pipes/devices without putting any of it back into the air (Unconfirmed).