Master in Chemical Technology

Surface and Interface Chemistry

Valentim M. B. Nunes

Engineering Unit of IPT

2014

Colloidal systems: Fundamentals and industrial importance. Liquid/gas Interface: surface tension; Young-Laplace equation; capillarity; vapor pressure and radii of curvature; Kelvin equation; surface excess quantities; Gibbs equation. Liquid-liquid Interface: scattering (work of cohesion and adhesion); interfacial tension; colloids aggregation; surfactants; emulsion stability (stabilizer agents and emulsifiers); Bancroft rule; phase inversion temperature (PIT). Solid/liquid Interface: wettability and contact angle; Young's equation; applications in detergency, oil extraction, paints and coatings. Solid/gas Interface: adsorption isotherms and their classification; specific area of solids; Langmuir and BET models ; adsorption on solids; heats of adsorption; main applications of adsorbents and catalysts with higher technological impact, namely activated coals and zeolites. Rheology.

Synopsys

Evaluation

Bibliography

Shaw, Introduction to Colloid and Surface Chemistry, 4th ed., Butterworth, Oxford, 1999Adamson, Physical Chemistry of Surfaces, 6th ed., Wiley Interscience, New York, 1997Hiemenz, Principles of Colloid and Surface Chemistry, 3rd ed., Marcel Dekker Inc., New York, 1997

Written test in frequency or final examination with a minimal mark of 10/20. Writing of a small monograph (10 to 15 page) about topics to distribute.

Colloidal Systems

Technological Importance

Colloidal systems: cosmetics; emulsions; foams; paints; plastics...

Processes involved: detergency; flotation; Ion Exchange; lubrication; clarification of water; explosives (transport); Agriculture (agrochemicals); construction and repair of roads (asphalt)…..

Important technologies Surface Chemistry in PharmacySurface 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

Colloidal systems contain particles with dimensions of the order of 10-9 to 10-6 m.

•Association Colloids: thermodynamically stable; ex. surfactant solution in water (micelles – c.m.c.) from a given temperature (kraft point).

•Real solutions of macromolecules: thermodynamically stable; e.g. glue.

•Colloidal dispersions: thermodynamically unstable due to the high interfacial tension.

Formation of micelles

Colloidal dispersionsDispersed phase Dispersant phase Name Examples

Liquid Gas Aerosol Fog; spray’s

Solid Gas Solid aerosol Industrial smoke; dust

Gas Liquid Foam Soap foam

Liquid Liquid Emulsion Milk; mayonnaise; asphalt; pharmaceutical creams

Solid Liquid Gel or suspension Inorganic colloids; toothpaste.

Gas Solid Solid foam Expanded polyurethane

Liquid Solid Solid emulsion jelly

Solid Solid Solid suspension Pigmented plastic