General characteristic of the dispersed systems Plan 1. The main concepts and determination 2. Classification of the dispersed systems 3. Preparation methods of the dispersed systems 4. purification methods of the dispersed systems Assistant Kozachok S.S. prepared

PHASES OF COLLOIDS THEIR CLASSIFICATION A colloidal solution is of heterogeneous nature. It consists of two phases i.e. a dispersed phase and a dispersion medium. Dispersed phase. It is the component present in small proportion and is just like a solute in a solution.

Classification of the dispersed systems according to the particle size Ultramicroheterogeneous ÷ м Microheterogeneous ÷ м Coarse-dispersion >10 -4 м

Colloidal particles can be classified according to shape as corpuscular, laminar or linear Many colloidal systems do, in fact, contain spherical or nearly spherical particles. Emulsions, latexes, liquid aerosols, etc., contain spherical particles. Certain protein molecules are approximately spherical. The crystallite particles in dispersions such as gold and silver iodide sols are sufficiently symmetrical to behave like spheres.

Some model representations for non-spherical particles

Classification of dispersed systems according to the particle-particle interaction Free dispersion or no sharp line of demarcation Free dispersion or no sharp line of demarcation (particles moving free) sols Not free dispersion or sharp line of demarcation (particle-particle interaction between themself) gels, foams

Classification of dispersed systems according to the particle-dispersion medium interaction Lyophilic (liquid- loving) good interaction of dispersed particle with dispersed medium emulsion and a water-in-oil Lyophobic (liquid- hating) (no any interaction of dispersed particle with dispersed medium)emulsion an oil-in water

Condensation methods of the preparation of the colloidal solutions. It bases on the appearing of a new phase in the homogenius phase according to the joining of molecules, atoms,ions. Physical Condensation from a pair, the substitution of a poor solvent Chemical FeCI 3 +3H 2 O → Fe(OH) 3 +3HCl AgNO 3 + KCl → AgCl + KNO 3 2H 2 S + SO 2 → 3S + 2H 2 O Ag 2 O + H 2 → 2Ag + H 2 O

Dispersion method of the preparation of colloid solution Mechanical Using crusher, mill, mixer Electrical using the instruments for electrolytic spraying Acoustic using ultrasound Peptisation Peptisation – chemical dispergation is transfering the sediment in the state of sol

Ball (а) and colloid (b) Ball (а) and colloid (b) mill а) b)b)b)b)

A further modification of dialysis is the technique of electrodialysis

Ultrafiltration: а) vacuum; b) preassure c) gel permeation chromatography а) b)b)

c) Another most valuable development of the ultrafiltration principle is the technique of gel permeation chromatography for the separation of the components of a polymeric sample and determination of the relative molecular mass distribution. The usual experimental arrangement involves the application of a pressure to force polymer solution through a chromatographic column filled with porous beads. The larger polymer molecules tend not to enter the pores of the beads and so pass through the column relatively quickly, whereas the smaller polymer molecules tend to diffuse through the pore structure of the beads and so take longer to pass through the column. The eluted polymer can be detected and estimated by measuring the refractive index of the emerging solution, and the relationship between retention time and relative molecular mass is determined by calibrating the apparatus with polymer fractions which have been characterised by other methods, such as osmotic pressure