How is oxygen purified?

Fractional distillation of liquid air. You need to be able to explain how nitrogen and oxygen are obtained from the air. You will recall that about 78% of the air is nitrogen and 21% is oxygen. These two gases can be separated by fractional distillation of liquid air

Oxygen is obtained on a commercial scale through the liquefaction and distillation of ambient air at air separation plants. A secondpurification process may be necessary if ultra-high purity levels are required. High-purity oxygen can also be produced through the electrolysis of water.