PowerPoint Presentation

Topic NameADSORPTION and EXSICCATION

PRESENTATION FLOW DefinitionTypesDifference between in its typesFactors affecting Pharmaceutical application

Definition

Adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface.ORThe process by which molecules of a substance, such as a gas or a liquid, collect on the surface of another substance.

Adsorption is the accumulation of atoms or molecules on the surface of a material. This process creates a film of the adsorbate (the molecules or atoms being accumulated) on the adsorbent's surface. It is different from absorption, in which a substance diffuses into a liquid or solid to form a solution.

ADSORBATE the substance which is adsorbed on the surface as known is adsorbate.

ADSORBENT the substance on which surface the adsorbate is adsorbed as known is adsorbent.

AdsorptionAbsorption

Types of adsorptionOn the basis of binding forces between the adsorbate and adsorbent the process of adsorption are classified into two types.Physical adsorptionChemical adsorption

Physical adsorptionits also called physio sorptionThat type of adsorption in which the adsorbate and adsorbent species are held together by vander waals forcesChemical adsorption Its also called chemosorption.that type of adsorption in which adsorbate and adsorbent are held together by chemical bonding with each other

Difference between physical and chemical adsorptionPhysical adsorptionChemical adsorptionCaused by intermolecular Vander Waals forcesCaused by chemical bond formationIts occurs at room temperatureIts occurs at high temperatureIt is a reversible processIt is irreversible processIt increases with increase in external pressureAn increase in pressure has no affectMulti layer adsorptionMono layer adsorptionNo activation energy is involved in this type of adsorptionActivation energy may be involved in this type of adsorptionLow temperature favorableIncrease in temp increases the chemosorption

FACTORS AFFECTING ADSORPTION Concentration of solute:It has direct effect on adsorption, i.e. if solute concentration is greater than adsorption is also greater.

Surface area The greater the specific area of the solid, the greater would be its adsorbing capacity.

Temperature:adsorption is an exothermic process, so when temperature is increased,physical adsorption decreased while chemical adsorption increased.

Effect of pressure: An increase in pressure causes an increase in the magnitude of adsorption of an adsorbent.

Pharmaceutical applicationIn the preparation of gas masks using activated charcoal to avoid poisonous gases like etc.Adsorption helps in desiccation process for example silica gel bags are used to protect the drug from moisture and other unfavorable environment.Adsorption chromatography is used to purify and separate pigments, hormones etc.

Used in the removal of pyrogens from injectable.The stability of emulsions is also affected by adsorption, for example an emulsifying agent is adsorbed at interface and stability is enhanced.The drug like kaolin and pectin are used as anti diarheals via process of adsorption.

ExsiccationExsiccation is the process of removing the water of crystallization from the hydrated crystalline substances by heating and making them less hydrous or anhydrous.

Example. For example, copper sulphate, CuSO4 . 5H20, when heated at about 30C loses two molecules of water of crystallization, at 100C it loses two more water molecules and the last and water molecule is removed when it is heated at 200C, thus forming CuSO4. 3H2O, CuSO4.H20 CuSO4 respectively. Similarly ferrous sulphate FeSO4.7H2O when heated on water bath loses six molecules of water of crystallization 'but when further heated to remove last water molecule, decomposition takes place. Hence ferrous sulphate with one molecule of water of crystallization FeSO4.H2O is called exsiccated ferrous sulphate.

Exsiccation Applications

Exsiccation is done to get an anhydrous product required in the formulation of certain medicaments. It is also carried out to reduce the bulk and weight of certain drugs so that they can be easily administered. Generally on exsiccation a fine powder of the substance is obtained.

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