- From Earth's Atmosphere: The most abundant source of oxygen is Earth's atmosphere, which contains approximately 21% oxygen by volume. Oxygen can be separated from the atmosphere through various methods, including cryogenic distillation, pressure swing adsorption (PSA), and electrolysis.
- Cryogenic Distillation: This method cools and compresses air until the oxygen liquefies. The liquefied oxygen can then be separated from other components of the air.
- Pressure Swing Adsorption: PSA involves passing compressed air through a series of molecular sieves that selectively adsorb nitrogen, allowing oxygen to pass through.
- Electrolysis: This process uses an electric current to split water molecules into hydrogen and oxygen.
- From Water (Electrolysis): Electrolysis of water can also be used to obtain oxygen. This method involves passing an electric current through water to split it into hydrogen and oxygen gas. The hydrogen and oxygen can then be collected separately. Electrolysis is commonly used in industries that require a high purity of oxygen.
- From Plants (Photosynthesis): Plants release oxygen as a byproduct of photosynthesis, a process by which they convert carbon dioxide and water into energy in the presence of sunlight.
- From Liquid Oxygen Storage Tanks: Many industries and healthcare facilities use liquid oxygen stored in tanks. Liquid oxygen is obtained from the separation of oxygen from the atmosphere or through the electrolysis of water.