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CHE 464 Submitted By: Merve Ece Akkan Submitted To: Assist. Prof. Ekrem Özdemir EXTRACTION




Extraction can be defined as the process of obtaining constituents by separating it from the crude material by the use of solvent/s. The primary ways of extraction of organic molecules of interest to biologist and medical investigators involve breaking of the cells. C riteria of extraction techniques is separating the soluble and insoluble components and leaving behind only insoluble cellular marc. THE CHEMISTRY OF EXTRACTION


The following need to be carefully evaluated when optimizing the design and operation of the extraction processes. Solvent selection ( Solvents differ in their extraction capabilities depending on their own and the solute’s chemical structure. ) Operating Conditions ( Depending on the nature of the extraction process, the temperature, pH and residence time could have an effect on the yield and selectivity. ) Mode of Operation ( Extractors can be operated in crosscurrent or counter-current mode. ) Extractor Type ( Important factors to consider when selecting extractor types are the stage requirements, fluid properties and operational considerations .) THE CHEMISTRY OF EXTRACTION




Selectivity : the ability to remove and concentrate the solute from the other components in feed. Availability : the inventory of solvent in the extraction system can represent a significant capital investment. Immiscibility : if the solvent is not immiscible with feed, reacovery of the solvent is required and it causes extra cost. Density differential : small density difference of solvent and feed causes separation problems, lower capacity and larger equipment. Reasonable physical properties: a too viscous solvent inhibits mass transfer . The boiling point should be very different than that of the solute (for recovery) Toxicity : The solvent should be non-toxic for health Corrosiveness Ease of recovery: solvent recovery needs to be as complete and pure as possible for recycle and preventing pollution. SOLVENT SELECTION FOR EXTRACTION


Compounds in a mixture are separated by their differential solubility in two immiscible solvents (one is usually water). The differential solubility is often expressed quantitatively as a partition coefficient . The partition coefficient is simply an equilibrium constant describing how much of a compound will be in each of the two immiscible solvents used in the extraction process. K= X/Y Equation 1 PARTITIONING


“K” value is based on the chemical potential “µ” of the solute at equilibrium is constant and equal in each phase: or; where the µ° s are chemical potentials in standard reference states. PARTITIONING Equation 2 Equation 3 Equation 4


Equation 5 Figure 1 PARTITIONING


The most obvious way to change µ °(L) is to choose a different extraction solvent V H , V L and V A are the partial molar volume of heavy, light solvent and solid respectively. When no single solvent has the desired solubility parameter, mixed solvents can be effective . CHANGES IN SOLVENT Equation 6




Temperature PH Residence Time OPERATING CONDITIONS


CROSS CURRENT EXTRACTION Batch and single stage continuous extraction are limited by equilibrium Cross-current extraction involves the use of fresh extracting solvent in each of the n stages COUNTER-CURRENT EXTRACTION Overcomes limitation imposed by equilibrium More uniform concentration driving force in the n stages Greater flexibility in process design Method of choice for large scale liquid-liquid extraction MODES OF OPERATION


Non-agitated gravity flow extractors * spray column * packed column Stirred gravity flow extractors * rotating disc contactor (RDC) column * Oldshue-Rushton column * raining bucket contactor TYPES OF EXTRACTION EQUIPMENTS

Non-agitated Gravity Flow Extractors :

Spray columns consists of an empty tower with inlet and outlet connection at the top and bottom, for introducing and removing the heavy and light liquid phases.  Since the spray column is essentially an empty vessel, there will be axial mixing making it difficult to obtain the equivalent of more than one or two theoretical stages. Non-agitated Gravity Flow Extractors Figure 3

Non-agitated Gravity Flow Extractors :

The packed tower is arranged such that the light phase is dispersed.  The heavy liquid is fed from the top and light liquid is fed from the bottom.  A large portion of the void space in the packing is filled with the continuous phase which flows downward.   The remainder of the void space is filled with drops of light liquid which rise through the continuous phase and finally coalesce to form a liquid-liquid interface at the top. Non-agitated Gravity Flow Extractors Figure 4

Stirred Gravity Flow Extractors:

The rotating disc contactor is a mechanically agitated, counter-current extractor. Agitation is supplied by a rotating disc, which usually runs at much higher speeds than a turbine type impeller. The disc contactor consists of a cylindrical column that is divided into number of compartments formed by a series of stator rings. Each compartment contains a centrally located, horizontal rotor disk that creates a high degree of turbulence inside the column. Stirred Gravity Flow Extractors Figure 5

Stirred Gravity Flow Extractors:

Oldshue-Rushton Column This column is similar to RDC but flat rotor discs are replaced with turbine type agitators . Raining Bucket Contactor This contactor consists of a series of scoops located on a slowly rotating, baffled rotor within a horizontal cylindirical vessel. Stirred Gravity Flow Extractors


Extraction with organic solvents Maceration Ext r action with water Steam distillation Other special methods Supercritical fluid extraction Microwave treatment Extraction by electric energy Sublimation Countercurrent extraction Ultrasound extraction EXTRACTION METHODS


Maceration is the process of extraction of a compound with the solvents for several days shaking or stirring at room temperature. Small sample is required Very simple process Time consuming in comparison to other methods This method does not totally extract the active ingredients. MACERATION


Steam distillation is another method for extracting active materials The material to be extracted is loaded onto perforated plates inside a cylindrical tank and steam is injected from below. The steam dissolves the desired substances and enters a condenser Distillation is complete when there is no more e x tract present in the condensate. STEAM DISTILLATION Figure 6


S upercritical fluid (SCF) : any compound at a temperature and pressure above the critical point . SCF can dissolve wide variety of organic compounds. SFE: the process of separating one component (the extractant ) from another (the matrix) using supercritical fluids as the extracting solvent. The basic principle of SFE : when the feed material is contacted with a supercritical fluid , the volatile substances will partition into the supercritical phase. After the dissolution of soluble material the supercritical fluid containing the dissolved substances is removed from the feed material. The extracted component is then completely separated from the SCF by means of a temperature and/or pressure change. The SCF is then may be recompressed to the extraction conditions and recycled. S UPERCRITICAL FLUID EXTRACTION

Advantages and Disadvantages of SFE:

SCF is easily recoverable from the extract due to its volatility Non-toxic solvents leave no harmful residue High boiling components are extracted at relatively low temperatures No thermal degradation Environmantally friendly High selectivity High pressure requirement High cost for equipment Advantages and Disadvantages of SFE Figure 7


The technology uses a microwave applicator as the energy source during solvent extraction leading to: faster processing time; improved yield and quality; direct extraction capability; lower energy consumption; reduced solvent levels; and lower capital investment, when compared to conventional extraction methods. MICROWAVE EXTRACTION Figure 8

Extraction by Electrical Energy:

Electrical energy accelerates the extraction and improves the yield. The high electric fields, typically 5–50 kV/cm , can cause electroporation and damage of membranes, enhance cytoplasmic ion leakage and release of intracellular bioproducts . Extraction by Electrical Energy


Sublimation is a technique use d to purify compounds . Typically a solid is placed in a sublimation apparatus and heated under vacuum. Under this reduced pressure the solid volatilizes and condenses as a purified compound on a cooled surface (cold finger), leaving a non-volatile residue of impurities behind. Once heating ceases and the vacuum is removed, the purified compound may be collected from the cooling surface . SUBLIMATION


This is a highly effective process whereby solvent flows in the opposite direction to material . Unlike maceration and percolation this method is continuous operation . COUNTER-CURRENT EXTRACTION

Solvent Requirement for Countercurrent Operation:

F = Feed quantity / rate, mass R = Raffinate quantity / rate, mass S = Solvent quantity / rate, mass E = Extract quantity / rate, mass The component mass balance : F X f + S Y s = R X r + E Y e F=R, E=S , Y s = 0, Y e = m X r (equilibrium relation) S = F/m (X f /X r –1) S olvent R equirement for C ountercurrent O peration Equation 7 Equation 8


Sound waves above 2000 Hz are used to accelerate the extraction. Utrasound achieves great penetration of a solvent into a plant tissue and improves the mass transfer. Ultrasonic waves generating cavitations disrupt cell walls and facilitate the release of matrix components. ULTRASOUND EXTRACTION Figure 9


Fractional extractions of two solutes in which both the heavy phase and light phase move countercurrently to each to other. The process separated one inital charge by periodically containing it with a stationary phase. A continuos feed is seperated by two countercurrently flowing solvents. Not only isolates the solute of interest, but also purifies it. FRACTIONAL EXTRACTIONS


The equilibrium constraint is Overall mass balance Solute mass balances So; FRACTIONAL EXTRACTIONS Equation 9 Equation 10 Equation 11 Equation 12


A solution containing the desired solute is mixed with a solvent immiscible with the solution . The initial solution is dilute and aqueous . The immiscible solvent is organic . The solute dissolves in the new organic solvent till it s concentration in water and organic are in equilibrium . In Figure 5.2-1 the equipments for the separation are shown. For small scale separatory funnel is used, the others are for the larger scales. BATCH EXTRACTIONS



Analytical Methods:

The concentrations can be calculated by writing two equations . The first one is equilibrium constraint . The second one is mass balance . Analytical Methods Equation 13

Analytical Methods:

y F is the solute concentration in the heavy feed.( In that equation it is assumed that the extraction solvent initially contains no solute and that both L and H are constant) When these two equations are combined. Analytical Methods Equation 14 Equation 15

Analytical Methods:

Here “E“ is the extraction factor The fraction extracted is given by; Analytical Methods Equation 16 Equation 17

Graphical Methods:

Easy to apply when the equilibrium is complex Graphical methods are the norm of advanced engineering Equilibrium constraint (it doesn`t have to be linear) The mass balance When both of these equations are plotted on the same graph, the intersection gives the values of x and y after the extraction. Graphical Methods Equation 18 Equation 19

Graphical Methods:

Graphical Methods Figure 10


The extractions discussed have been the major method of isolating biological solutes, many of which have been antibiotics. These extractions take a clarified beer or cell fraction containing perhaps milligrams per liter, and produce an extract whose concentration may be several percent by weight. Where applicable, extractions can be a cornerstone of biological separations. CONCLUSIONS

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