1. Chemistry

2. Session
Surface Chemistry - 1

3. Introduction Importance of Surfaces Development of Surface Chemistry
Surface Sensitivity and Specificity
The Surface Science Approach
Surface Analytical Techniques
The Need for Ultra-high Vacuum (UHV)
Experimental Surface Science Systems

4. Surfaces reactions everywhere
Background
Surfaces reactions everywhere
Washing clothes
Brushing teeth
Preventing food to stick to pans
Surface chemistry important to a wide range of technologies
Catalysis
Semiconductor Fab
Paints & finishes
Consumer products

5. Why are surfaces important
Catalysis
Pollution
Corrosion
Sensors
Energy
Conversion
Electronic
Devices
Surface
Processes

6. Surface Chemistry
the 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

7. Phenomena in Surface Chemistry
Wetting, Spreading and Penetration
Foam Breaking in Aqueous Systems
Solubilization
Rheological Effects in Surfactant Phases

8. 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

9. 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

10. 1. Gas-Liquid and Liquid-liquid Interfaces

11. Surface Tension, 
an effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet

12. Surface Tension as a Force
caused by the attraction between the molecules
of the liquid by various intermolecular forces

13. تطبيقات كيمياء السطوح والحفز
تعد تطبيقات السطوح كثيرة ولاحصر لها ومنها : 1- الحفز 2- المنظفات ( إزالة الأوساخ ) 3- الفصل الكروماتوجرافي ( الفصل اللوني ) 4- طفو المعادن 5- طرد الماء 6- التبادل الأيوني 7- الصباغة 8- الدهانات معالجة المياه
هل لديك تطبيقات أخرى؟

14. مقدمة للجزء الأول (التوتر السطحى)
هل فكرت يوماً كيف تقف بعض الحشرات على الماء دون حراك؟ هل فكرت كيف تستطيع وضع إبرة حديدة بحيث تطفو على سطح الماء؟! كل هذا.. تجاوبه ظاهرة طبيعية.. ظاهرة التوتر السطحي.

15. تعريف التوتر السطحى
التوتر السطحي
هو ذلك التأثير الذي يجعل الطبقة السطحيّة لأي سائل تتصرف كورقة مرنة. ذلك التأثير الذي يسمح للحشرات . بالسير على الماء، والأشياء المعدنية الصغيرة كالإبر، أو أجزاء ورق القصدير من الطفو على الماء ، وهوالمسبب أيضا للخاصية الشعرية.

16. هناك تعريفان التوتر السطحى
تعريف التوتر السطحى
هناك تعريفان التوتر السطحى
التعريف الأول : هو الشغل المبذول لزيادة مساحة سطح السائل بمقدار وحدة المساحات و وحداته هى جول/ م2 .
التعريف الثانى : هو القوة السطحية المؤثرة عموديا على وحدة الأطوال من سطح السائل. و وحداته هى نيوتن/ متر  و يتضح أن

17. سبب ظاهرة التوتر السطحي
جزيئات السائل التي في داخل السائل تتعرض لقوى متساوية في جميع الاتجاهات، بينما الجزيئات التي على سطح السائل تتعرض لقوى تجذبها نحو عمق السائل الأمر الذي يجعل جزيئات السطح تتصرف وكأنها غشاء مشدود
يحدث التوتر السطحي بسبب التجاذب بين جزيئات السائل بواسطة التغير في قوى الجزئيات الداخلية. معظم السائل كل جزيء يسحب بالتساوي في جميع الإتجاهات بواسطة جزيئات السائل المجاورة ، ومحصّلة هذه القوى صفر.عند سطح السائل تسحب الجزيئات بواسطة الجزيئات الأخرى الأعمق في السائل ولكن ليست الجاذبية كجاذبية الجزيئات المجاورة لها في الوسط من حيث الشدّة (تكون كضغط هواء أو سائل آخر). لذلك كل الجزيئات عند السطح تكون عرضة لقوى داخليّة من التجاذب الجزيئي الذي من الممكن أن يكون متَّزن فقط مع مقاومة السائل للضغط. ولذلك يغير السائل شكله حتى يشغل أقل مساحة سطح ممكنة. A B

18. Interface is the boundary between two or more phases exist together
The properties of the molecules forming the interface are
different from those in the bulk that these molecules are
forming an interfacial phase.
Several types of interface can exist depending on whether
the two adjacent phases are in solid, liquid or gaseous state.
Important of Interfacial phenomena in pharmacy:
Adsorption of drugs onto solid adjuncts in dosage forms
Penetration of molecules through biological membranes
Emulsion formation and stability
The dispersion of insoluble particles in liquid media to form
suspensions.

19. LIQUID INTERFACES Surface and Interfacial Tensions
In the liquid state, the cohesive forces between
adjacent molecules are well developed.
For the molecules in the bulk of a liquid
They are surrounded in all directions by other molecules for which they have an equal attraction.
For the molecules at the surface (at the liquid/air interface)
Only attractive cohesive forces with other liquid molecules
which are situated below and adjacent to them.
They can develop adhesive forces of attraction with the
molecules of the other phase in the interface
The net effect is that the molecules at the surface of the
liquid experience an inward force towards the bulk of the
liquid and pull the molecules and contract the surface with
a force F .

20. To keep the equilibrium, an equal force must be applied to
oppose the inward tension in the surface.
Thus SURFACE TENSION [γ ] is the force per unit length that must be applied parallel to the surface so as to counterbalance the net inward pull and has the units of dyne/cm
INTERFACIAL TENSION is the force per unit length existing at the interface between two immiscible liquid phases and has the units of dyne/cm.
Invariably, interfacial tensions are less than surface tensions because an adhesive forces, between the two liquid phases forming the interface are greater than when a liquid and a gas phase exist together.
If two liquids are completely miscible, no interfacial tension exists between them.
Greater surface tension reflects higher intermolecular force of attraction, thus, increase in hydrogen bonds or molecular weight cause increase in ST

21. The work W required to create a unit area of surface is known as SURFACE FREE ENERGY/UNIT AREA (ergs/cm2)
erg = dyne . cm
Its equivalent to the surface tension γ
Thus the greater the area A of interfacial
contact between the phases, the greater the free energy.
W = γ ∆ A
For equilibrium, the surface free energy
of a system must be at a minimum.
Thus Liquid droplets tend to assume a spherical shape since a sphere has the smallest surface area per unit volume.

22. Methods for measuring surface and interfacial tension
Measurement of Surface and Inter­facial Tensions
Methods for measuring surface and interfacial tension
1- Capillary rise method
2- Ring (Du Nouy) tensiometer
3- Drop weight method (Stalagmometer)
The choice of the method for measuring surface
and interfacial tension depend on:
Whether surface or interfacial tension is to be determined.
The accuracy desired
The size of sample.

23. Session Objectives Adsorption Adsorption versus absorption
Types of adsorption: physisorption and chemisorption
Desorption
Adsorption isotherms: Freundlich and Langmuir
Adsorption isobar
Catalysis

24. Adsorption
The phenomenon of higher concentration of any molecular species at the surface than in the bulk
Adsorbent
The substance on the surface of which adsorption takes place is called adsorbent
Adsorbate
The substance which is being adsorbed on the surface of another substance.
Desorption
The process of removal of an adsorbed substance from the surface on which it is absorbed

25. Adsorbent Materials Activated Carbon Activated Alumina Silica Gel
Molecular Sieves (Zeolites)
Polar and Non-polar adsorbents

26. Activated carbon
Made from nutshells, wood, and petroleum, bituminous coal by heating in the absence of oxygen to dehydrate and carbonize (remove volatile components),
"Activation" is the process that produces the porous structure essential for effective adsorption by oxidation of carbon with water vapor or CO2.
Activated carbon attracts non-polar molecules such as hydrocarbons.
Typical surface areas are 300 to 1500 m2/g.

27. Adsorption vs absorption

28. Types of Adsorption
Positive adsorption occurs when the concentration of adsorbate is higher on the surface of adsorbent than in the bulk.
Negative adsorption occurs when the concentration of adsorbate is less on the surface of adsorbent than in the bulk.

29. Types of adsorption
Physical adsorption
Chemical adsorption

30. Factors affecting adsorption
Effect of adsorbate: The easily liquifiable gases like NH3, HCl, CO2 etc. are adsorbed to a greater extent than the permanent gases such as H2 ,O2, N2, etc.
Effect of specific area of the absorbent: The greater the specific area of the solid, the greater would be its adsorbing capacity.
Effect of temperature:adsorption decreases with increase in temperature.
Effect of pressure: An increase in pressure causes an increase in the magnitude of adsorption of an adsorbent.

31. Freundlich Isotherm
A graph between the amount (x/m) adsorbed by an adsorbent and the equilibrium pressure of the adsorbate at constant temperature is called adsorption isotherm
At low pressure the graph is nearly straight line
At high pressure x/m becomes independent of p
Over a narrow range of p

32. Freundlich Isotherm

33. Langmuir isotherm f: fraction of surface area covered
p: partial pressure of the adsorbate f
m: mass of adsorbate adsorbed per unit mass of adsorbent
1-f
Rate of adsorption
Rate of desorption
At equilibrium, ra = rd;
Mono-layer coverage

34. Langmuir adsorption isotherm:
Combining equations (1) and (2):
a = ka x ka’/kd
b = ka/kd
The values of constants ‘a’ and ‘b’ depend upon the nature of adsorbate, nature of solid adsorbent and temperature.

35. Summary of adsorption isotherms
Easy to fit
adsorption data
Chemisorptions and physisorption
Freundlich
Useful in analysis of reaction mechanism
Chemisorption and physisorption
Langmuir
Note
Application
Isotherm equation
Name

36. Adsorption isobar
Graph between the amount adsorbed(x/m) and temperature at a constant equilibrium pressure of adsorbate gas is known as adsorption isobar
Chemisorption isobar shows an initial increase with temperature and then expected decrease .The initial increase is because of the fact that the heat supplied acts as activation energy required in chemisorption.

37. Application of Adsorption
In clarification of sugar
In gas masks
In catalysis
In adsorption indicators
In chromatographic analysis
In softening of hard water
In preserving vacuum
In paint industry
In removing moisture from air in the storage of delicate instruments

38. Need to make chemicals faster
Most Reactions are too slow to be useful...

39. Ways to Make Chemicals Faster
Disadvantage--Too hot!
Temperature
Pressure
Disadvantage--Cause Explosions
Catalysts!!!!
Disadvantage--Costly
Add other Chemicals
Disadvantage--Separate chemicals

40. The Story of Catalysis Why Catalysis ? What is a Catalyst ?
How Catalysts Work ?

41. Role of a Catalyst Catalysts speed up a chemical reaction
without being used up...
Catalyst + Reactants
Catalyst-Reactants
Catalyst + Products

42. Hydrogenation of alkene

43. Important properties of catalyst
Activity: A reasonable rate of reaction is needed.
Selectivity: Byproducts should be minimized.
Cost: The acceptable cost depends upon the catalyst lifetime and product value.

44. Catalysis
Positive catalysis
Negative catalysis
Auto catalysis

45. Catalysis Types of catalysis Homogeneous catalysis
Process Products Catalyst
1. Hydrolysis of an ester. Acid and Alcohol H+
2. Oxidation of SO2 to SO3 SO3 NO
in lead chamber process
Heterogeneous catalysis
Process Products Catalyst
1. Ammonia synthesis NH3 Fe with Al2O3
2. Methanol synthesis MeOH ZnO/Cr2O3

46. Catalysis Enzyme catalysis Reaction Catalyst Invertase 2. Zymase
A coenzyme is an organic non-protein molecule that is a functional part of an enzyme. Coenzymes are not used up in the reactions in which they assist

47. Do Catalysts Live Forever?
NO!!!
They can die from:
-- poisons which contaminate the catalyst
-- large molecules which cover the catalyst
-- over heating, over pressurizing
-- crumbling/crushing

48. Automotive Emission Control
Automobile catalytic converters need to catalyze several reactions
– CHx + O2 CO2 + H2O
– CO + O2  CO2
– NOx +CHx  N2 + H2O + CO2
– This is achieved by the use of a supported precious metal catalyst like platinum, palladium etc.
– Catalyst needs O2 to operate, CeO2 acts as a temporary regenerable source of O2.
CeO2  Ce2O3 + 1/2O2

49. Thank you