General characteristic of the dispersed systems

Plan1. The main concepts and

determination2. 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 CLASSIFICATIONA 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

Ultramicroheterogeneous10-7 ÷ 10-9 м

Microheterogeneous10-4 ÷ 10-7 м

Coarse-dispersion>10-4 м

Colloidal particles can be classified according to shape as

corpuscular, laminar or linearMany 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 Free dispersion or no no sharp line of sharp line of demarcation demarcation (particles moving free)

sols

Not free dispersion or Not free dispersion or sharp line of sharp line of demarcationdemarcation

(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

FeCI3+3H2O → Fe(OH)3 +3HCl

AgNO3 + KCl → AgCl + KNO3

2H2S + SO2 → 3S + 2H2O

Ag2O + H2 → 2Ag + H 2O

Dispersion method of the preparation of colloid solution

Mechanical

Using crusher, mill, mixer

Electrical

using the instruments for electrolytic sprayingAcoustic

using ultrasound

PeptisationPeptisation – chemical dispergation is transfering the

sediment in the state of sol

BallBall (а) (а) andand colloidcolloid ( (bb) ) mill

а)а) bb))

A further modification of dialysis is the technique of electrodialysis

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

а) 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