A desalination apparatus is disclosed which uses a salt sponge unit to remove a majority of salt from water. A parallel plate capacitor can be connected after the salt sponge to remove remaining salt ions. The salt sponge is a nanoporous, high surface area carbon scaffold to which crown ethers are attached. A power supply is connected to the salt sponges for applying a bias voltage to regenerate the salt sponges. A chlorine treatment unit can be connected after the parallel plate capacitor. A method of purifying sea water using the apparatus also is disclosed.