separationtechniques-introduction-190810143855.pdf

separationtechniques-introduction-190810143855.pdf

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  SEPARATION TECHNIQUES - INTRODUCTION SIVASWAROOPYARASI
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  DEFINITION: Separation techniques arethose techniques that can be used to separate two different states of matter such as liquids and solids. Separation processes or a separation method or simply a separation is methodology to attain any mass transfer phenomenon that convert a mixture of substances into two or more distinct product mixtures. Separation is an important asset to purify component of interest from a mixtures.
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  NEED OF SEPARATION TECHNIQUES: TOIDENTIFY WHAT TO BE SEPARATED FROM MIXTURE. TO OBTAIN IMPORTANT AND PURE SUBSTANCES. TO REMOVE UNWANTED PARTICLES.
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  TYPES OF SEPARATIONTECHNIQUES: • Separation techniques are classified based on type of mixtures: Separation techniques For solid in liquid mixtures Homogenous: 1. Evaporation 2. Distillation 3. centrifugation Heterogenous: 1. Sedimentation / gravitation 2. Filtration 3. Magnetic separation 4. Fractional distillation For liquid in liquid mixtures Homogenous: 1. Simple or fractional distillation. 2. Chromatography Heterogenous: 1. Partition separation using funnel
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  MAGNETIC SEPARATIO N: This method involvesthe separation of magnetic substances from non-magnetic substances by means of magnet. Takes advantage of physical property of magnetism, so it useful only for certain substances such as ferromagnetic (materials strongly affected by magnetic fields) and paramagnetic (materials that are less affected, but the effect is still noticeable). This method involves the separation of magnetic substances from non-magnetic substances by means of magnet.
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  • Applications: • Wastemanagement, low-magnetic field separation in water purification and separation of complex mixtures. • To remove metal contaminants from pharmaceutical product streams. • Magnetic cell separation. It is currently being used in clinical therapies, more specifically in cancer and hereditary diseases researches. • These techniques are combined with PCR (polymerase chain reaction), to increase sensitivity and specificity of results.
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  DECANTATION: Decantation is aprocess for the separation of mixtures of immiscible liquids or of a liquid and a solid mixture such as a suspension. Immiscible liquid separation: • Takes advantage of differences in density of the liquids. • A separatory funnel is an alternative apparatus for separating liquid layers. It has a valve at the bottom to allow draining off the bottom layer. It can give a better separation between the two liquids. • Example: separation of mixture of oil and water.
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  •Takes advantage ofgravity/sedimentation of solids in case solid-liquid separation. •Sedimentation: The tendency of particles in suspension to settle down in the fluid due to certain forces like gravity, centrifugal acceleration, or electromagnetism is called as sedimentation. •The solid that gets settled down is called as sediment. •In laboratory it can be done in test tubes. To enhance productivity test tubes should be placed at 45° angle to allow the sediments to settle at the bottom of the apparatus. •A decanter centrifuge may be used for continuous solid-liquid separation. Liquid-solid separation:
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  Examples/applications: • Decantation isfrequently used to purify a liquid by separating it from a suspension of insoluble particles. • Decantation is also present in nanotechnology. In the synthesis of high-quality silver nanowire (AgNW) solutions and fabrication process of high-performance electrodes, decantation is also being applied which greatly simplifies the purification process. • Fat is determined in butter by decantation. • In sugar industry, processing of sugar beets into granular sugar many liquid - solid separations are encountered.
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  FILTRATION: Takes advantage ofphysical property of state of matter, its size and solubility in liquid. • The substance which is left behind in the filtration medium is called residue. • The liquid which passes through the filtration medium is called filtrate. Mechanical, physical or biological operations that separates solids from fluids (liquids or gases ) by adding a medium through which only the fluid can pass can be called as filtration.
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  Applications: Most important techniquesused by chemists to purify compounds. HEPA filters in air conditioning to remove particles from air. In the laboratory, a Büchner funnel is often used, with a filter paper serving as the porous barrier.
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  CENTRIFUGATION: It is usedto separate mixtures where the solid particles don’t settle faster and which are of very small size and can't be separated by filtration. Centrifugation is a technique which involves the application of centrifugal force to separate particles from a solution according to their size, shape, density, viscosity of the medium and rotor speed. A centrifuge is a device that separates particles from a solution through use of a rotor.
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  More-dense components ofthe mixture migrate away from the axis of the centrifuge (move to the outside), while less-dense components of the mixture migrate towards the axis, i. e., move to the center. The rate of centrifugation is specified by the angular velocity usually expressed as revolutions per minute (RPM), or acceleration expressed as g. The conversion factor between RPM and g depends on the radius of the centrifuge rotor.
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  Applications/examples: Microcentrifuges are usedto process small volumes of biological molecules, cells, or nuclei. Used in diagnostic laboratories for blood and urine tests. Aids in separation of proteins using purification techniques such as salting out. Differential Centrifugation used to separate organelles and membranes found in cells.
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  EVAPORATION: Evaporation is typeof vaporization that occurs on the surface of liquid as it changes into gas phase. This separation technique can be used to separate solutes that are dissolved in solvent, by boiling the solution. The solvent gets vaporized leaving back the solute. Factors affecting: • Concentration of the substance evaporating in the air. • Flow rate of air, pressure, temperature. • Surface area. • Intermolecular forces.
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  Evaporation equipment: Natural circulation evaporators: Evaporating still and pans. Evaporating shorttubes. Forced circulation evaporators. Film evaporators: Climbing film evaporators. Horizontal film evaporators.
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  Applications/examples: • Recovering saltsfrom solution. • The use of evaporation to dry or concentrate samples is a common preparatory step for many laboratory analyses such as spectroscopy and chromatography. • Demineralization of water.
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  DISTILLATION: Distillation is an effectivemethod to separate mixtures comprised of two or more pure liquids (called “components”). The separation of a mixture of liquids based on the physical property of boiling point. Distillation is a purification process where the components of a liquid mixture are vaporized and then condensed and isolated. The mixture is heated until one of the components boils (turns to a vapor). The vapor is then fed into a condenser, which cools the vapor and changes it back into a liquid that is called distillate. What remains in the original container is called the "residue".
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  Simple distillation :
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  Fractional distillation :
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  Types: Simple: Used toseparate liquid mixtures which boil without decomposition and have enough difference in their boiling points. Applications: Separation of acetone and water. Distillation of alcohol. Fractional: Fractional distillation is used for the separation of a mixture of two or more miscible liquids for which the difference in boiling points is less than 25K. The apparatus for fractional distillation is like that of simple distillation, except that a fractionating column is fitted in between the distillation flask and the condenser. Applications: Separation of different fractions from petroleum products. Separation of a mixture of methanol and ethanol.
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  Other applications/examples: Separation ofvolatile oils. Separation of drugs obtained from plant or animal sources – vitamin A from fish liver oil. Purification of organic solvents. Manufacture of official preparations – spirit of nitrous ether, spirit of ammonia, distilled water, and water for injection. Refining petroleum products.
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  CRYSTALLIZATION: • Crystallization isthe (natural or artificial) process by which a solid forms, where the atoms or molecules are highly organized into a structure known as a crystal. • Used to separate a dissolved heat-liable (will decompose upon heating and hence can sublime) solid (solute) from a solution. • Most minerals and organic molecules crystallize easily, and the resulting crystals are generally of good quality, i.e. without visible defects.
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  First, the solutionis heated to evaporate off most of the solvent to make a hot and nearly saturated solution. After which, the hot solution to is kept for cooling, naturally. The solubility of the solute decreases as the solution is cooled, and the excess solute which can no longer be dissolved in the saturated solution crystallizes out of the solution. The crystals which are formed can be separated from the remaining solution by filtration.
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  •Purification of drugs. •Separationof crystals of alum from impurities sample. •Fractional Crystallization : It is possible to separate mixtures of different ionic compounds having identical chemical composition by dissolving them in water and adjusting the temperature of the solution so that one compound crystallizes out and the other does not. •E.g. K2SO4 and KNO3 Applications/ examples:
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  SUBLIMATION SEPARATION: • Sublimation isthe transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase. • This technique takes the advantage of substance’s sublimable property. • Separate a mixture of solids containing one which sublimes and one (or more than one) which does not, by heating the mixture.
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  Applications/examples: • Separate iodinefrom sand. • Dye-sublimation printers help in rendering digital pictures in a detailed and realistic fashion which helps in the analysis of substances. • Sublimation finds practical application in forensic sciences. • Chemists usually prefer sublimation as a purification method to purify volatile compounds.
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  CHROMATOGRAPHY: • Chromatography isa separation technique used to separate the different components in a liquid mixture. • The mixture is dissolved in a fluid called the mobile phase, which carries it through a structure holding another material called the stationary phase. • Chromatography is vast separation technique which has many methods or has different principles of separation involved.
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  EXTRACTION TECHNIQUES: • Involvesthe separation of medicinally active portions of plant or animal tissues from the inactive or inert components by using selective solvents in standard extraction procedures. • Different methods of extraction are:
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  Method Solvent TemperaturePressure Time Volume of organic solvent consumed Polarity of natural products extracted Maceration Water, aqueous and non-aqueous solvents Room temperature Atmospheric Long Large Dependent on extracting solvent Percolation Water, aqueous and non-aqueous solvents Room temperature, occasionally under heat Atmospheric Long Large Dependent on extracting solvent Decoction Water Under heat Atmospheric Moderate None Polar compounds Reflux extraction Aqueous and non-aqueous solvents Under heat Atmospheric Moderate Moderate Dependent on extracting solvent Soxhlet extraction Organic solvents Under heat Atmospheric Long Moderate Dependent on extracting solvent Pressurized liquid extraction Water, aqueous and non-aqueous solvents Under heat High Short Small Dependent on extracting solvent Supercritical fluid extraction Supercritical fluid (usually S-CO2), sometimes with modifier Near room temperature High Short None or small Nonpolar to moderate polar compounds Ultrasound assisted extraction Water, aqueous and non-aqueous solvents Room temperature, or under heat Atmospheric Short Moderate Dependent on extracting solvent Microwave assisted extraction Water, aqueous and non-aqueous solvents Room temperature Atmospheric Short None or moderate Dependent on extracting solvent Pulsed electric field extraction Water, aqueous and non-aqueous solvents Room temperature, or under heat Atmospheric Short Moderate Dependent on extracting solvent Enzyme assisted extraction Water, aqueous and non-aqueous solvents Room temperature, or heated after enzyme treatment Atmospheric Moderate Moderate Dependent on extracting solvent Hydro distillation and steam distillation Water Under heat Atmospheric Long None Essential oil (usually non- polar)
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