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P .K CHOURASIA PRESENTS
• SURFACE CHEMISTRY
Surface Chemistrythe study of physical and
chemical phenomena that occur at the interface of two phases, including solid-liquid interfaces, solid-gas interfaces, solid-vacuum interfaces, and liquid-gas interfaces
P henomena in S urface Che mistry
1. Wetting, Spreading and Penetration2. Foam Breaking in Aqueous Systems 3. Solubilization 4. Rheological Effects in Surfactant Phases
Assignment-6
GGrouproup P Presentationresentation G9 : Foam breaking and its application G10G10 : : Solubilization and its application G11 : Rheology and its application
(5 min)
Surface Chemistry in Important Technologies
Surface Chemistry in Pharmacy Surface Chemistry in Food and Feed Surface Chemistry in Detergency Surface Chemistry in Agriculture Surface and Colloid Chemistry in Photographic Technology
Surface Chemistry in Paints Surface Chemistry of Paper Surface Chemistry in the Polymerization of Emulsion Colloidal Processing of Ceramics Surface Chemistry in Dispersion, Flocculation and
Flotation Surface Chemistry in the Petroleum Industry
Assignment-7
1. Search from Journals or websites to find some examples of Surface Chemistry in
Important Technologies 2. Write up a 1 page concise report in A4 paper.3. Report is due on September 15, 2009. (10 points)
Individual Report
Analysis and Characterization in Surface Chemistry
Measuring Equilibrium Surface Tensions Measuring Dynamic Surface Tensions Measuring Contact Angle Determining Critical Micelle Concentration Measuring Micelle Size and Shape Identification of Lyotropic Liquid Crystalline Mesophases Characterization of Microemulsion Structure Measuring Particle Size by Light Scattering Measurement of Electrokinetic Phenomena in Surface
Chemistry Measuring Interactions between Surfaces Measuring the Forces and Stability of Thin-Liquid Films Measuring Adsorption
Surface Tension, an effect within the surface layer of a
liquid that causes that layer to behave as an elastic sheet
Surface Tension as a Force
caused by the attraction between the molecules of the liquid by various intermolecular forces
Surface Tension as Surface Excess Free Energy
. ,
Capillary Rise Method
whereh = the height the liquid is lifted,
la - = the liquid air surface tension (J/m² or N/m)θ = contact angle ρ = density of liquid (kg/m3 )g = acceleration due to gravity (m/s²)r = radius of tube (m)
Determination Methods
The Ring Method
RF
4 =
where =constant
(Du Nouy tensiometer)
Pendant Drop Method
mg = 3a cos()
is the surface tension of liquid is the contact angle at which a liquid/vapor interface meets the solid surface .
Contact Angle Goniometer .
Surface tension (mN m-1) ofsome liquids
0oC 20oC 40oC 60oC 80oC 100oCH2O 75.64 72.75 59.56 66.18 62.61 58.85Ethanol 24.05 22.27 20.60 19.01 - -Acetone 26.20 23.70 21.20 18.60 16.20Toluene 30.74 28.43 26.13 23.81 21.53 19.39Benzene 31.60 28.90 26.30 23.70 21.30Hg (0oC) 480 Ag (970oC) 800NaCl (1080oC) 94 AgCl (452oC) 125
Intermolecular forcesIntermolecular forces
Surface Tension Directly depends on
intermolecular forces in the solution
Inversely depends on temperature
of metallic liquid > ionic liquid > covalent liquid
Liquid in a Vertical Tube
ls = liquid-solid surface tensionla = liquid-air surface tension= contact angle
Concave
Convex
Concave Adhesive>>Cohesive
Convex Adhesive<<Cohesive
Interface Tension and Spreading
Spreading Coefficient, Sin Water at 20oC
liquid B n-hexadecane 72.8-(30.0+52.1) = - 9.3 Drop on water surfacen-octane 72.8-(21.8+50.8) = + 0.2 Spreadingn-octanol 72.8-(27.5+8.5) = +36.8 Spreading against
inpurity
S =
OWOAWA S =
Use the following data of the surface/interface tensions (mN m-1) at 20oC
A B A B AB
H2O C6H6 72.75 28.88 35.0
H2O CCl4 72.75 26.28 45.0
H2O Hg 72.75 470 375 H2O C8H15OH 72.75 17.0 10.7
predicts the spreading behavior of B on A
Surface Tension of SolutionSubstances in solution :Surface active agent “Surfactant” (<o)
hydrophilic part hydrophobic part
Surface inactive agent (>o) such as ionic compounds, acids, bases etc.
Surface Tension of Some Alcohols in Water at 20oC
Surfactants in solution
Micelle formationwhen C > CMC
CMC determination
CMC = critical micelle concentration
Effect of Temperature on Surface tension
T
Pure liquid
Surfactant solution
Gibbs isotherm
is known as surface concentration (mol/m2) C is the concentration of the substance in the bulk solution. R is the gas constant T the temperature
Effect of Concentration on Surface tension
AdsorptionOn
surface
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