Mixture Separation Techniques

• Liquid-liquid mixture
• Liquid-gas mixture
• Gas-gas mixture

Separation Techniques

• Suitable for different phases of organic compounds.
• Solid-solid mixture: sieving
  • Magnetic seperation.
  • Hand picking (depends on the particle size).
  • Klinnowing
• Solid-liquid mixture:
  • When a soluble solvent stops dissolving in a solvent, the solution is said to be saturated.

Separation Techniques

• Filtration
• Decantation
• Sedimentation

Apparatus for Filtration

• Receiving flask.
• Filter paper.
• Funnel.
• Filtration separates a solid-liquid immiscible mixture where the solute does not dissolve in the solvent.
• Filtration is the fastest way of separating a mixture.
• Decantation is for solid-liquid immiscible mixtures.
• Evaporation also can separate a solid-liquid mixture.
• Crystallization is suitable for separation of solid-liquid immiscible mixtures.
• Crystallization obtains a pure organic compound by dissolving the organic compound in a suitable solvent that dissolves the compound completely at elevated temperature but not at room temperature, followed by filtration.
• Adsorbents can remove contaminants or impurities.
• Use a suitable solvent during crystallization/recrystallization (a solvent that does not dissolve the compound completely at cold or room temperature but dissolves it when heated).
• Adsorbents can be silica, alumina, or activated charcoal.

Steps for Crystallization

• Obtain a suitable solvent.
• Heat the solution to dissolve the solute.
• Add adsorbent to help remove impurities while still heating.
• Filter while hot.
• Leave the solution to cool down at room temperature or in ice to allow crystals to grow.
• Filter the solution to obtain pure crystals.
• First filtration targets the filtrate, second targets the residue.
• Solid-gas mixture: sublimation or steam distillation.
  • Steam distillation is good for gas immiscible mixture.

Liquid-Liquid Mixture

• Distillation
  • Simple distillation.
  • Fractional distillation.
  • Vacuum distillation.
• Fractional distillation separates gas-gas mixtures.
• For separating liquid-liquid miscible mixtures:
  • Steam distillation
  • Simple distillation
  • Vacuum distillation
  • Chromatography
• For separating liquid-liquid immiscible mixture, differential extraction is used.
• A separating funnel is used during differential extraction.
• Distillation is the separation of organic mixtures based on their boiling points via heating.

Apparatus for Distillation

• Collecting flask.
• Condenser (converts gaseous vapor into liquid).
• Quick-fit flask.
• Chromatography separates organic compounds based on how well they are retained in the stationary phase under the influence of a mobile phase.
• Retention on a stationary phase is the Retention Factor.
• The obtained value/retention factor is known as the Rf value.
• Rf value for an organic compound is usually less than 1.
• Rf value = (Distance moved by the compound) / (Distance moved by the solvent).
• Stationary phase is a solid coated on / poured into a glass column/plate that retains the organic compound while it moves under the influence of a mobile phase.
• Materials used as stationary phases include silica gel, alumina, or cellulose.
• Mobile phase is a liquid or gaseous solvent that carries the organic compound through the stationary phase.
• Chromatography can be adsorption or partition types.
• Adsorption chromatography has subtypes: thin layer, preparative thin layer, and column.
• Partition chromatography can be divided into gas-liquid, liquid-liquid, paper chromatography, etc.
• Liquid-gas mixture processes: gravity, centrifugation, compression
  • Any gas separation.
• Gas-gas mixture: fractional distillation
• When a mixture of organic compounds has one compound that decomposes close to its boiling point, use vacuum distillation.
• When the boiling point of the organic compound is less than 25°C, use simple distillation.