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

1. Gas-Liquid and Liquid-liquidInterfaces

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