Electrolysis

An electric current is pushed through a liquid or molten salt, pulling elements apart and collecting them at the electrodes.

12 lines that use it

Aluminum 5 stations · 6 raw sources Bleach 7 stations · 10 raw sources Caustic soda 5 stations · 2 raw sources Chlorine 5 stations · 4 raw sources Copper 6 stations · 4 raw sources Hydrogen 6 stations · 2 raw sources Iridium 6 stations · 8 raw sources Manganese 6 stations · 7 raw sources Nickel 5 stations · 4 raw sources Potassium hydroxide 5 stations · 2 raw sources Silver 6 stations · 8 raw sources Zinc 6 stations · 4 raw sources

What it looks like on the line

Caustic sodaElectrolyze it in membrane cells. Current splits the brine. Chlorine bubbles off at one electrode and hydrogen at the other, while sodium ions slip through the membrane into the cathode chamber and pair with hydroxide ions to form caustic soda.
AluminumRun the current through the pot. A low direct-current voltage, under 5 volts, but at 100 to 300 kiloamperes, runs through the bath. Oxygen from the alumina burns the carbon anode away to carbon dioxide, and aluminum is deposited on the cell floor. Pots run around the clock so the bath never freezes.
NickelLeach and plate it. In one refining route the matte is leached into a nickel salt solution, and the nickel is electroplated from solution onto cathodes as electrolytic nickel.
BleachElectrolyze the brine. Brine flows through a cell divided by a membrane. Current pulls chlorine out at one electrode and makes hydrogen and caustic soda at the other. The chlorine-alkali process uses a lot of electricity per tonne of sodium hydroxide.
IridiumCollect the anode mud. During electrorefining of copper and nickel, noble metals do not dissolve. They settle to the bottom of the cell as anode mud, along with silver, gold, selenium and tellurium. This sludge is the starting point.
ZincPlate it out electrically. An electric current passes through the solution in a hall of cells, and zinc deposits on aluminum sheets used as cathodes, while oxygen forms at the anodes. The cells stay at 30 to 35 °C, and the sulfuric acid they make is returned to the leach tanks.
ChlorineRun current through the cells. In each membrane cell, chloride ions give up electrons at the anode and become chlorine gas. Only sodium ions can pass through the membrane, and at the cathode water breaks into hydrogen gas and hydroxide.
Potassium hydroxideRun current through the cell. Electrolysis gives potassium hydroxide in solution, hydrogen at the cathode and chlorine at the anode. The anode and cathode spaces must be kept apart.
SilverElectrolyze to fine silver. The final purification is electrolysis in a silver nitrate solution. This gives silver of over 99.9 percent purity, and higher grades above 99.999 percent are also made.
ManganesePlate it out. The solution goes to an electrowinning plant, where an electric current deposits pure manganese metal.
CopperPlate pure copper by electrolysis. The anodes hang in baths of copper sulfate and sulfuric acid, facing thin sheets of pure copper or stainless steel. Current drives copper off the anode and onto the cathode, and valuable silver, gold, selenium and tellurium fall to the bottom as anode slime.
HydrogenSplit water with electricity. Electrolyzers pass electric current through water and collect hydrogen at one electrode. When the power comes from wind or solar, the product is called green hydrogen.