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Definition - What does Supernatant mean?

The supernatant is the clear liquid that lies above the solid residue after centrifugation, precipitation, crystallization or settling. The liquid is normally free of precipitate and has a lower density. The process leading to the supernatant formation is used in separating the several components making up a complex mixture. The supernatant liquid is used in the preparation of green clay eluate (CE) which is one of the components in the corrosion inhibitors for steel used in saline waters.

Supernatant is also known as supernate.

Corrosionpedia explains Supernatant

Centrifugation is one of the processes used in separating the components of a complex mixture. The process which is performed in the lab involves spinning the samples at high speeds using a centrifuge. This subjects the particles of the mixture to centrifugal forces that cause denser particles to migrate away from the axis of rotation while light particles move towards this axis. The dense particles sediment at the bottom and this is referred to as a pellet. The remaining solution or the isolated specimen is known as the supernatant. The supernatant is composed of the lighter particles which make it to float over the denser sediment or precipitate.

The supernatant can then be analyzed further or processed for other uses as happens in the preparation of corrosion inhibitors. The supernatant is used in various industries and helps in analyzing the properties of several materials and components. It is widely used in the corrosion and bio-corrosion industry either for analyzing or making the corrosion inhibitors.

Typical applications include:

  • Bio-corrosion - Human osteoclasts (OC) have properties that cause corrosion of surgical instruments and metallic implants. Centrifugation of the human OC mixture is performed to produce the supernatant. The extent of biocorrosion is then quantified by measuring the concentration of the metal ions released into the supernatant.
  • Purification of water to remove copper in the water generated by the PCB processes in the electronics industry. The supernatant in this case contains the excess corrosive copper. By eliminating this supernatant, the waste water becomes free of the corrosive and toxic properties and hence environmentally friendly.
  • Trace mercury detection in liquid metals.
  • Preparation of corrosion inhibitors for the carbon steel in saline solutions. The inhibitor is comprised of gluconate, zinc sulphate and the clay eluate. The required concentration of the clay eluate is produced by centrifugation and then using the supernatant produced.
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