Zaporozhye state medical University Department of physical and colloid chemistry

1. Zaporozhye state medical University Department of physical and colloid chemistry COLLOID CHEMISTRY

2. 1. Heterogeneity (multiphase). 2. Dispersion (fragmentation). Signs of colloid chemistry objects Colloidal chemistry is sometimes called PHYSICOCHEMISTRY disperse systems

3. Types of disperse systems

4. Classification by degree of interaction dispersion phase with the dispersion medium Lyophilic - a systems, where interaction of the particles of the dispersed phase with the solvent is highly expressed. Lyophobic - dispersion phase interacts weakly with the dispersion medium. Hydrophilic (a) and hydrophobic (b) surface in a three phase system - water - solid - air; 1 - Water 2; - Solid; 3 - air; a - wetting angle.

5. 1.Excess surface energyGS Features of colloidal systems 2. Thermodynamic instability 3. Irreproducibility 4. Capacity to structure formation

6. Dispersion methods Obtaining disperse systems -grinding large sample substance to disperse particles sizes;

7. Colloid mills Allow to reach more subtle grinding

8. Intensification of dispersion INTENSIFICATION OF THE PROCESSES OF DISPERSION BY INTRODUCTION OF SURFACE-ACTIVE SUBSTANCES AND IONS OF ELECTROLYTE ALSO USED FOR MORE SUSTAINABLE DISPERSE SYSTEMS The mechanism of action is in the formation on the interface environment-particle adsorption layers.

9. Condensation methods • based on the association of molecules in aggregates from true solutions; • used to obtain highly dispersed systems; • do not require the cost of external work; • emergence of a new phase occurs at a supersaturation environment.

10. 1. Germ-formation - the emergence of centers of crystallization. Condensation stage 2. Growth of the germ. 3. Formation of a layer of stabilizer (DEL).

11. 1. Method of condensation of vapor - the formation of mist in the gas phase at low temperatures. 2. Method of replacing the solvent - is poured into a solution of a liquid substance in which the substance is substantially insoluble. Physical condensation methods

12. STRUCTURE OF COLLOID MICELLES • According to the standard theory of micellar sol consists of 2 parts: • Micella - colloidal structural unit, surrounded by an electric double layer. • Intermicellar fluid - the dispersion medium, separating the micelles, where the electrolytes, non-electrolytes and surfactants are soluted.

13. STRUCTURE COLLOID MICELLES Micelle structure can be considered only as a first approximation, because it has no specific composition.

14. With an excess of one reactant microchip adsorbs its ions, which do not form a precipitate. As a result of this microchip acquires a charge, ions, informing him that the charge potential-called, and he charged crystal - core micelles. I Charged core attracts ions from the solution with the opposite charge - counterions; interfacial electrical double layer is formed. Some part of counterions adsorbed on the surface of the nucleus, forming a so-called adsorption layer counterions; nucleus together with adsorbed thereon are called counterions colloidal particles or granules. The remaining counter, the number of which is determined on the basis of the rules of electrical micelles constitute a diffuse layer of counterions; counterions adsorption and diffusion layers are in a state of dynamic equilibrium adsorption - desorption.

15. Rule of Fajans-Peskov: • "On the surface of the solid assembly is primarily adsorbed ions which: • included in the assembly; • able to complete construction of the crystal lattice of the unit; • form compounds with ions of the unit; • are isomorphic with the ions of the unit. " Rule Paneth-Fajans Determine the sign of the surface charge of AgI (cryst.) obtained by the reaction: АgNО3(s) + КI(s) = АgI(cryst.) + KNO3(s) а) nАgNО3 = nКI : surface sediment is not charged; б) nАgNO3 > nКI : в) nАgNО3 < nКI : excess АgNO3Аg+ + NО3-excess КI К+ + I- АgI +АgI - + - + -

16. Methods based on the formation of poorly soluble compounds by chemical reactions. 1. Reduction reaction. Recovery of sodium aurate by formaldehyde. 2NaAuO2 + 3HCOH + Na2CO3 = 2Au + 3HCOONa +NaHCO3 + H2O Micelle structure : Chemical condensation methods

17. 2. Exchange reaction. Obtaining of Prussian blue sol. 3K4[Fe(CN)6] + 4FeCl3 Fe4[Fe(CN)6]3 + 12KCl Micelle structure : {[mFe4[Fe(CN)6]3·n[Fe(CN)6]4-]4n-·4 (n-х)K+}4x-·4xK+ {[m Fe4[Fe(CN)6]3·nFe3+]3n+·3(n-х)Сl-}3x+·3xCl-

18. 2. Exchange reaction. Obtaining of silver iodide sol. AgNO3 + KJ(exc.) = AgJ↓ + KNO3 Micelle structure :

19. 3. Oxidation reaction Formation sulfur sol. 2H2Sр-р + O2 = 2S ↓+ 2H2O Micelle structure :

20. 4. Hydrolysis reaction Obtaining ferric hydroxide sol. FeCl3 + 3H2O = Fe(OH)3 ↓ + 3HCl Micelle structure :

21. Peptization - a method based on transferring a colloid precipitation primary dimensions are dimensions which are highly dispersed systems. The essence of the method: freshly fallen loose sediment is converted into sol by treatment peptizing agents. Peptization method

22. Methods of cleaning of disperse systems Low molecular weight impurities destroy colloidal systems. Dialysis - separation of low molecular weight impurities sols through a semipermeable membrane.

23. Methods for cleaning of disperse systems Desalination by electrodialysis. Under the action of electric current salt ions begin to move: positive – The cathode to the anode and the negative Low molecular weight impurities destroy colloidal systems. Electrodialysis - dialysis, accelerated by an external electric field.

24. Methods for cleaning of disperse systems Low molecular weight impurities destroy colloidal systems. Ultrafiltration - the electrodialysis under pressure (hemodialysis).

25. Zaporozhye state medical University Department of physical and colloid chemistry Molecular-kinetic properties of dispersion systems

26. Brownian motion Colloidal particles by molecular-kinetic properties are not fundamentally different from true solutions. Weighted particles in the solution are in constant random thermal motion.

27. Brownian motion The collision of particles is an exchange of energy and as a result the average kinetic energy is set, same for all particles.

28. Diffusion Diffusion - spontaneous process of alignment of particle concentration throughout the volume of solution or gas under the influence of thermal motion. Einstein studied the Brownian motion, he established the diffusion coefficient - D connection with an average shift: Einstein showed that the diffusion coefficient D is related to the size of the diffusing particles equation: r – the radius of the spherical particles whose size is much larger than the size of the solvent molecules

29. The osmotic pressure Osmotic pressure in colloidal systems is a very small amount, it is difficult reproducible experiments. Osmotic pressure in colloidal systems is inversely proportional to the cube of the particle radius: – osmotic pressure in a total sols same substances with different particle dispersion

30. Sedimentation Sedimentation (from Lat. Sedimentum - sediment) is the process of sedimentation of dispersed particles in a liquid or gaseous medium under the influence of gravity. Emergence of particles is called reverse sedimentation. Sedimentation rate of the particles obeys the law Stokes : • ρ, ρ0- and medium density particles; • ήviscosity of the medium; • r - radius; • g- acceleration of gravity If the difference ρ-ρ0 has the sign «-» medium particles are lighter and float

31. Sedimentation analysis For sedimentation analysis of kinetically stable systems to determine the size and mass of the particles is not enough force gravity. Russian scientist AV Dumanskiy (1912) proposed to expose colloidal systems centrifugation. Swedberg (1923) developed a special centrifuge with great speed, called the ultracentrifuge.

32. Ultracentrifugation Modern ultracentrifugation allow to obtain a centrifugal force in excess of the acceleration of gravity 105. Modern ultracentrifuge - complex apparatus central part rotor of which (with speed 20-60000 rev / min and up).

33. Zaporozhye state medical University Department of physical and colloid chemistry Optical properties of disperse systems

34. The scattering of light This is the most characteristic optical property of colloidal systems. The light is scattered in all directions. This phenomenon was observed Faraday (1857) in the study of gold sol. The phenomenon Tyndall in 1868. Through pure liquids and molecular solutions light just passes. Through colloidal dispersions light ray meeting on the way a particle is not reflected, as if it skirts, and rejected several changes its direction (diffraction). Faraday Tyndall

35. Vessel with a colloidal solution light source There is a frosted glow lenses The scattering of light Tyndall found that when illuminated colloidal solution bright light ray path it is visible when viewed side as a luminous cone - Tyndall cone.

36. Zaporozhye state medical University Department of physical and colloid chemistry Electrical properties of disperse systems

37. DEL. Formation of a double electric layer DEL existence of ions and the potential jump at the interface of the two phases plays an important role in many phenomena important for theory and practice . These include: the electrode processes , electrocapillary and electrokinetic phenomena , phenomena associated with the electrostatic interaction of colloidal particles , largely determine the stability of the dispersed system . All these phenomena are interconnected through DEL , called Electrosurface . There are three possible mechanisms for the formation of DEL : • Due to the transition of electrons or ions from one phase to another ( 1st variant ); • As a result of the selective adsorption of ions in the electrolyte interphase layer ( 2nd variant ); • As a result of the orientation of the polar molecules conjugated phases in their interaction ( third variant ) .

38. When immersed in water, the metal plate portion of the positive ions, which are located in the crystal lattice as a result of interaction with the dipoles of water will go into solution.

39. Electric double layer 2nd version. In the formation of AgI sol by reaction between AgNO3 and KI at AgI microcrystals adsorbed ions (Ag +, I-). If an excess of silver nitrate, the silver ions are adsorbed. When this solid phase is positively charged (variant b). Excess anions NO3-ions are attracted to the Ag + Salt Salt

40. Electric double layer third variant. • When the orientation of polar molecules at the interface in the presence of metal ions. At the same potential-anions are polar (example) fatty acids metal ions fatty acid solid surface

41. The structure of DEL. First picture of DEL was expressed Kwinke (1859) and developed in the works of Helmholtz (1879). DEL theory was developed in the works of scientists of the USSR A.N. Frumkin and B.V. Deryagin. The first theory was the theory of the structure of DEL Helmholtz: DEL consists of two flat charges located at the molecular distance from one another and interact with each other only by electrostatic forces of attraction.

42. Structure of DEL Gouy-Chapman model assumed location counterions diffusion under the influence of forces acting in opposite directions: the electrostatic forces of attraction to the surface and forces the thermal motion of the ions. The theory introduces the concept of the diffusion layer, the ions are treated as point charges that do not have their own size.

43. Structure of DEL According to modern concepts (Stern’s theory) structure of DEL: ions are included in the solid phase, form the inner lining of the double layer, ions of opposite sign, i.e. counterions forming an outer lining, wherein the counterions part is in direct contact with ions of the solid phase, forming a dense layer, and another part is counterions diffused layer.

44. Within the limits of DEL operates the electric field the intensity of which is characterized by the value potential. The potential change in DEL depending on the distance shown in pic. In this case the potential drop within the dense layer is linear, and in the diffusion layer - exponentially. On a solid surface charge arises, called φ-potential. Sign φ-potential coincides with the sign of the charge and its potentsal-forming ions calculated by the Nernst equation. φ-potential is the work of a single transfer (elementary) charge from infinity far place to the surface of the solution volume of the solid phase Potential at the interface Δ and potential so-called plane as close as possible (within a distance of the order of molecular dimensions δ) φ0 belong to the category of almost immeasurable value.

45. The electrokinetic potential (zeta potential) - potential arising at the boundary AB sliding phase when relative movement in an electric field. This potential is calculated from the experimental data for the equation Helmholtz -Smoluchowski To characterize the electrical properties of the surface using ζ-potential-potential boundary sliding phases determined experimentally by various methods. ζ-potential can be represented as the work necessary for the transfer of charge from the unit element of an infinitely distant volume of solution on the sliding surface. ζ-potential sign coincides with φ-potential U0 – velocity of the fluid, 0 – constant,  - dielectric permittivity a liquid, E – the electric field strength,  - potential, - fluid viscosity.  = *U0/0**E

46. Electrokinetic phenomena. Classification. Electrokinetic phenomena of the 1st kind - relative movement phases under the influence of the potential difference Electrokinetic phenomena 2nd kind - the emergence of a potential difference due to the forced displacement relative phases Electrophoresis - motion of dispersed particles in an electric field Potential sedimentation - the emergence of a potential difference in the motion of particles in a stationary liquid Electroosmosis - the movement of the dispersed medium in the electric field of the dispersed phase relative to the stationary Potential flow - the emergence of a potential difference in fluid motion relative to a stationary solid surface

47. Electrophoresis The presence of particles dispersed systems of electric charge was discovered In 1808 a professor at Moscow University F.F. Reuss in studies of water electrolysis. Reiss put two experiments. In the first he used a U-shaped tube, in the second dipped two glass tubes in the clay. By passing a DC clay particles move toward the positive electrode. Electrophoresis mechanism is that under the influence of an electric field ions double layer is torn at the boundary of the slip, the particle acquires a charge, and moves to the oppositely charged electrode, counter ions move in the reverse direction.

48. Electrophoresis Particle velocity of the dispersed phase electrophoresis and speed dispersion medium when electroosmosis directly proportional to the electric field E and the dielectric constant ε of the dispersion medium and inversely proportional to the medium viscosity η. Particle velocity of the dispersed phase electrophoresis U related to the value ζ-potential of the equation Helmholtz-Smoluchowski U0 = 0**E*/ Electrophoresis allows to deliver the drug directly to the affected area and gradually establish there a sufficient concentration.

49. Electroosmosis In the second experiment Reiss filled the middle part of the U-shaped glass tube with powdered quartz, poured water, loaded electrodes and passed the direct current through. After some time, the water level in the knee with increased negative electrode, and the second knee - dropped. This phenomenon is called electroosmosis.

50. Potential of leakage and sedimentation Potential leakage (the effect of Kwinke) is a phenomenon of the potential difference in the dispersion medium motion relative to the fixed dispersion phase. Sedimentation potential (Dorn effect) - the emergence of a potential difference in induced motion of the dispersed phase relative to the fixed dispersion medium.