adsorption

Question 1

introduction

Answer 1

 It is a surface phenomenon and refers to the uniform distribution of a substance through another at the
surface.
 It is the phenomenon in which a layer of ions, molecules or aggregates of molecules condense upon
the surface with which they come in contact.

Question 2

importance

Answer 2

The term surface is customarily used when referring to a gas / solid or a gas / liquid interface. This
phenomenon is a significant factor as:
 Adjuncts in dosage forms
 Penetration of molecules through biological membranes
 Emulsion formation
 Stability and the dispersion of insoluble particles in liquid media to form suspension

Question 3

adsorption

Answer 3

It is an accumulation of substance at the interface or boundary between two and heterogeneous phases.
For example, Solid-Gas, Oil- H2O, Gas-Liquid, or Solid-Liquid.

Question 4

absorption

Answer 4

It implies the penetration one component throughout the body of a second. The distinction between
adsorption and absorption is not always clear.

Question 5

components of adsorption

Answer 5

Adsorption consists of two components:
 ADSORBENT: Adsorbant is the substance which adsorbs the other substance at its surface. E.g.
Kaolin, pectin, altpulgite, talc, Magnisum trisilicate, Al(OH)3, Simithicone, CaCO3 (Activated
Charcoal), Mg(OH)3 etc.
 ADSORBATE: Adsorbate is the substance which is adsorbs on the other substance’s. E.g. Toxins,
Strychnine HCl, Digoxin and many other drugs

Question 6

examples

Answer 6

 Stychinine HCl onto Activated Charcoal (Solid – Liquid)
 Activated Charcoal used in Respirators for civilian and forces (Solid- Gas)
 Decrease in surface tension is due to surface active agent for example liquid-gas bonding.
 Emulsifying agent as emulsion stabilizers in case of liquid- liquid bonding.

Question 7

factor affecting adsorption

Answer 7

Factor Affecting Adsorption:
 Solubility of adsorbate
 Nature of Adsorbate
 Nature of adsorbent
 Surface area of absorbant
 Affinity between adsorbent and adsorbate
 Concentration of both adsorbate and adsorbent
 Pressure
 Temperature

Question 8

types of adsorbents

Answer 8

 Oxygen containing compounds
o Typically, hydrophilic and polar
o E.g. silica gel, zeolites
 Carbon based compounds
o Typically, hydrophobic and non-polar
o E.g. activated carbon, graphite
 Polymer based compounds
o Polar or Non polar functional groups in a porous polymer matrix
o Examples: Polymers & Resins

Question 9

classification of adsorbents based on pore size

Answer 9

 Microporous Adsorbents
o Pore Size Range - 2 Ao to 20 Ao
 Mesoporous Adsorbents
o Pore Size Range - 20 Ao to 500 Ao
 Macroporous Adsorbents
o Pore Size Range - > 500 Ao

Question 10

silica gel

Answer 10

o Drying of refrigerants, organic solvents, transformer oils
o Desiccants in packing & double glazing
o Dew Point Control of natural Gas

Question 11

activated alumina

Answer 11

o Drying of gases, organic solvents, transformer oils
o Removal of HCl from Hydrogen
o Removal of fluorine in alkylation process

Question 12

activated carbon

Answer 12

o Removal of odors from gases
o Recovery of solvent vapours
o Nitrogen from air
o Water purification
o Purification of He

Question 13

polymer and resins

Answer 13

o Water Purification
o Recovery & purification of steroids & amino acids
o Separation of fatty acids from water & toulene
o Recovery of proteins & enzymes

Question 14

clay

Answer 14

o Treatment of edible oils
o Removal of organic pigments
o Refining of mineral oils
o Removal of poly chlorinated biphenyls (PCBs)

Question 15

zeolites

Answer 15

o Oxygen from air
o Drying of gases
o Drying of refrigerants & organic liquids
o Pollution control including removal of Hg
o Recovery of fructose from Corn Syrup

Question 16

application

Answer 16

5. Preparative and Analytical Chromatography
6. Heterogeneous catalysis
7. Water purification
8. Solvent recovery

Question 17

pharmacy applications

Answer 17

1. ADSORPTION OF NOXIOUS SUBSTANCE FROM ALIMENTARY CANAL: Universal and
   antidote (activated charcoal, MgO and Tannic acid) when used orally, reduces toxic levels of poisoning.
2. REMOVAL OF TOXIC ELEMENTS FROM BLOOD: Some adsorbents are used to remove toxic
   elements by subjecting its dialysis through “hemodialysis” membrane over charcoal and adsorbents
   (chlorpheniramine, colchicine, Phenytoin, aspirin etc.)
3. ADSORPTION PROBLEMS IN DRUG FORMULATION: Drugs containing antacids and other drugs,
   when given, the above problem results. Adsorbents are non-specific nutrients, drugs and enzymes when given
   orally. Example: promazine given above or adsorbents.

Question 18

more pharmacy applications

Answer 18

3. TREATMENT OF SEVERE DRUG OVERDOSES:
    Extracorporeal method has been developed named “Haemoperfusion”.
    Microencapsulation of activated charcoal by Arcylic Hydrogel, a biocompatible material preventing
   Embolism and removal of platelets.
    In vivo – In vitro relationship regarding adsorptive capacity of adsorbents.
    No relationship exists.
    Reason:
   o GIT and biological system have many other things which alter the adsorption ratio.
    Example:
   o In vitro – 5g activated charcoal bin 8g of Aspirin
   o In vivo – 30g of activated charcoal inhibits the GIT adsorption of 3g of Aspirin by 50%.