THE 9 MOST COMMON MIXTURE SEPARATION TECHNIQUES - CHEMISTRY - 2025

The choice of mixture separation techniques is based on the type of mixture and the difference in the chemical properties of the components of a mixture (Amrita University & CDAC Mumbai, SF).

Most of the materials in our environment are mixtures of two or more components. The mixtures are homogeneous or heterogeneous. Homogeneous mixtures are uniform in composition, on the contrary, heterogeneous mixtures are not.

Air is a homogeneous mixture and oil in water is a heterogeneous mixture. Homogeneous and heterogeneous mixtures can be separated into their components by various physical methods.

In a chemical reaction, it is important to isolate the component (s) of interest from all other materials so that they can be further characterized.

Biochemical systems studies, environmental analysis, pharmaceutical research, these and many other areas of research require reliable separation methods (Separating Mixtures, SF).

Mixes come in many forms and phases. Most of them can be separated, and the type of separation method depends on what type of mixture it is.

Common methods of separating mixtures

Filtration

Filtration is a method used to separate pure substances into mixtures made up of particles, some of which are large enough to be captured with a porous material.

The particle size can vary considerably, given the type of mixture. For example, stream water is a mixture that contains natural biological organisms such as bacteria, viruses, and protozoa.

Some water filters can filter bacteria, whose length is on the order of 1 micron. Other mixtures, like soil, have relatively large particle sizes, which can be filtered through something like a coffee filter.

Decantation

When the densities of two liquids that are immiscible with each other are to be separated, this method can be used.

The separatory funnel helps to collect trailer fluids separately. In the case of solids, the lighter solids can be separated by decanting it in aqueous medium when both solids are not soluble. When blowing air the separation can also be done with very light and heavy solid mixtures.

Sublimation

It is the physical property of some substances to go directly from the solid state to the gaseous state without the appearance of the liquid state.

Not all substances have this characteristic. If one component of a mixture is sublimated, this property can be used to separate it from the other components of the mixture.

Iodine (I ₂), naphthalene (C ₁₀ H ₈, naphthalene balls), ammonium chloride (NH ₄ Cl) and dry ice (solid CO ₂) are some substances that sublimate (PHYSICAL SEPARATION TECHNIQUES, SF).

Evaporation

Evaporation is a technique used to separate homogeneous mixtures where there is one or more dissolved solids.

This method expels the liquid components from the solid components. The process typically involves heating the mixture until no more liquid remains.

Before using this method, the mixture should contain only one liquid component, unless it is not important to isolate the liquid components.

This is because all liquid components will evaporate over time. This method is suitable for separating a soluble solid from a liquid.

In many parts of the world, table salt is obtained from the evaporation of seawater. The heat in the process comes from the sun (CK-12 Foundation, SF).

Simple distillation

Simple distillation is a method used for the separation of components of a mixture that contains two miscible liquids that boil without decomposition and have a sufficient difference in their boiling points.

The distillation process involves heating a liquid to its boiling points and transferring the vapors to the cold part of the apparatus, then condensing the vapors and collecting the condensed liquid in a container.

In this process, when the temperature of a liquid increases, the vapor pressure of the liquid increases. When the vapor pressure of the liquid and the atmospheric pressure reach the same level, the liquid changes to its vapor state.

Vapors pass over the heated portion of the apparatus until they come into contact with the cool surface of the water-cooled condenser.

When the steam cools, it condenses and passes through the condenser and is collected in a receiver through the vacuum adapter.

Fractional distillation

When the difference in boiling points are close to each other and not much, a detailed distillation is carried out which is called fractional distillation. It is carried out in a column called a fractionation column.

The fractionation column allows the condensation of different solvents at different temperatures and return the fraction of the mixture to the flask.

Petroleum distillation takes place in the multi-component fractionation column over a wide range of temperatures.

Melting point differences can also be used in the same way as boiling point in separating mixtures.

Icebergs are formed which are solidified fresh water and is based on the depression of the freezing point phenomenon (Tutorvista.com, SF).

Chromatography

Chromatography is a family of analytical chemistry techniques for the separation of mixtures. It involves passing the sample, a mixture containing the analyte, in the 'mobile phase', often in a solvent stream, through the 'stationary phase'.

The stationary phase delays the passage of the sample components. When components pass through the system at different speeds they are separated in time, like runners in a marathon.

Ideally, each component has a characteristic time to pass through the system. This is known as "retention time."

A chromatograph takes a chemical mixture carried by liquid or gas and separates it into its components as a result of differential distributions of solutes as they flow around or over a stationary solid or liquid phase.

Various techniques for the separation of complex mixtures are based on the differential affinities of substances for a gaseous or liquid mobile medium and for a stationary adsorbent medium through which they pass. Such as paper, gelatin or magnesium silicate gel (Separation Techniques, SF).

Centrifugation

In centrifugation, a liquid is spun so rapidly that the particles separate. Differences in densities cause heavier particles to sink to the bottom and lighter particles to accumulate on top.

Doctors separate blood samples for analysis (study) using a centrifuge (Kindersley, 2007).

Magnetic separation

Electrolytes and non-electrolytes, magnetic and non-magnetic substances can be separated by this separation technique using electric field or magnetic field.

References

1. Amrita University & CDAC Mumbai. (SF). Separation of Mixtures Using Different Techniques. Taken from amrita.olabs.edu amrita.olabs.edu.in
2. CK-12 Foundation. (SF). Methods for Separating Mixtures. Taken from ck12.org ck12.org
3. Kindersley, D. (2007). SEPARATING MIXTURES. Taken from factmonster factmonster.com
4. PHYSICAL SEPARATION TECHNIQUES. (SF). Taken from ccri.edu ccri.edu
5. Separating Mixtures. (SF). Taken from eschooltoday eschooltoday.com
6. Separation Techniques. (SF). Taken from kentchemistry kentchemistry.com