Swim / sink method

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The float / sink method is a very simple method for separating two solids . The process only works if the materials to be separated have different densities .

It is used by adding a mixture of two substances to a liquid bath whose density is between the densities of the substances to be separated. Water is often used for this. One substance then sinks to the bottom due to its higher density, while the second substance floats on the surface due to its lower density. After using the method, the liquid bath can be carefully decanted and filtered in order to obtain both substances separately.

The float / sink process is often used when recycling plastics. Another option is cutting metals.

Magneto-gravimetric method

To separate non-magnetic mixtures, when ferrofluid is used as the liquid bath (separation medium), in addition to gravity, a further force can be selectively exerted on the separation medium by a magnetic field. This results in a variable apparent density of the separation medium. In this way, you can achieve a very high degree of separation, or you can separate mixtures with components of high density (gold, lead, copper ...) Even fractions with a lower density than the basic density of the separation medium can be separated if the magnetic field is arranged accordingly. This process is also known as MDS (magneto density separation). Compared to conventional separation media for high density (mercury, gallium), water-based ferrofluids are cheaper, less toxic and hardly harmful to the environment.

One of the first commercial separation systems to operate with ferrofluid was the Magstream model from Intermagnetics General Corporation (IGC) in the 1980s. Currently (2016) some more modern MDS separation systems for metal and plastic separation are put into operation worldwide.

Individual evidence

  1. Sink bath tub on navarini.com
  2. Metal recycling (PDF; 1.5 MB) ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. on bmukk.gv.at @1@ 2Template: Webachiv / IABot / www.bmbf.gv.at
  3. Example of a system manufacturer: http://www.liquisort.com