Zeolite Oxygen Concentrators

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    Context 

    •  In India, IISc has transferred the technology of making Zeolite oxygen concentrators to over 20 companies.

    About Zeolites 

    • Zeolites are highly porous, 3-D meshes of silica and alumina.
    • They occur naturally and are also produced industrially on a large scale. 
      •  In nature, they occur where volcanic outflows have met water
      • Synthetic zeolites have proven to be a big and low-cost boon. 
    • They are often also referred to as molecular sieves.
    • The zeolites are noted for their lability toward ion exchange and reversible dehydration. 
    • They have a framework structure that encloses interconnected cavities occupied by large metal cations (positively charged ions) and water molecules.

    Zeolite oxygen concentrators

    • One biomedical device that has entered our lexicon during the pandemic is the oxygen concentrator. 
      • This device has brought down the scale of oxygen purification from industrial-size plants to the volumes needed for a single person. 
    • At the heart of this technology are synthetic frameworks of silica and alumina with nanometer-sized pores that are rigid and inflexible
    • Beads of one such material, zeolite 13X, about a millimetre in diameter, are packed into two cylindrical columns in an oxygen concentrator.

    How does it work?

    • Zeolite performs the chemistry of separating oxygen from nitrogen in the air.
    • Being highly porous, zeolite beads have a surface area of about 500 square meters per gram. 
    • At high pressures in the column, nitrogen is in a tight embrace, chemically speaking, with the zeolite. 
    • Interaction between the negatively charged zeolite and the asymmetric nucleus (quadrupole moment) of nitrogen causes it to be preferentially adsorbed on the surface of the zeolite.
    • Oxygen remains free and is thus enriched. 
    •  Once nitrogen is under arrest, what flows out from the column is 90%-plus oxygen. 
      • After this, lowering the pressure in the column releases the nitrogen, which is flushed out, and the cycle is repeated with fresh air.

    Source: TH