Topic outline

  • General

    The aim of the course is to provide a broad, fundamental basis in surface and colloidchemistry and its applications.

    The main objectives are:

    Colloidal systems and their classifications.

    Prediction of the phase behaviour of multicomponent systems in terms of molecular properties and self-assembly.

    The nature of surface active agents and the driving forces for their adsorption to various types of interfaces.

    Interfacial charging mechanisms

    The stability of a colloidal system in terms of the surface forces acting between the constituent particles and behaviour in response to changes in composition.

    Surface chemical principles involved in industrial processes such as froth flotation, paper making and detergency.


  • Introduction to the colloid chemistry and surface phenomena

    What are the colloids and interfaces? Why are they important? Why do we studythem together?Three ways of classifying the colloids. How to prepare colloid systems? Key properties of colloids.


    Abstract

    Colloid and surface chemistry is a core subject of physical chemistry. It is a highly interdisciplinarysubject, of interest to diverse fields of science andengineering (pharmaceuticals, food, cosmetics, detergents,medicine and biology, up to materials andmicroelectronics, just to mention a few). Colloids are characterized by their many interestingproperties (e.g. kinetic or optical) as well as byobserving their stability over time.Colloidal systemsare composed of small particles dispersed in amedium.The fact that these particles have such small dimensionsis the reason that a huge surface (interfacial) areais created. Their high interfacial area is the reason whycolloidal systems have special properties and also whywe study colloids and interfaces together.Colloids and interfaces are present and of importancein many (everyday) products and processes, rangingfrom food, milk and pharmaceuticals to cleaningagents, and paints or glues.Most of these products are colloidal systems, e.g. milk(liquid emulsion) or paint (emulsions or dispersions).The production and/or use of many colloidal-basedproducts involve knowledge of surface science, e.g.the adhesion of glues and paints or cleaning with detergents.


  • Colloid stability

    Colloid Structure. The generation of colloidal charges in water.The theory of the diffuseelectrical double-layer. The zeta potential. Polymer-Induced Colloid Stability. Systems containing lyophilic material. The flocculation of colloids. The interaction between two charged surfaces in water.Lyophobic sols.DLVO theory. Critical coagulation concentration and the Hofmeister series.

     

    Abstract

     

    The stability of many colloidal solutions depends critically on the magnitudeof the electrostatic potential at the surface of the colloidalparticles. One of the most important tasks in colloid science is thereforeto obtain an estimate of the electrostatic potential under a wide range of electrolyte conditions.In practice, one of the most convenient methods for obtainingelectrostatic potential uses the fact that a charged particle will move at some constant, limitingvelocity under the influence of an applied electric field.The zeta potential - ZP (symbol ζ) is related to the surface charge, a property that all materials possess, or acquire, when suspended in a fluid. The sign and magnitude of ZP affects process control, quality control, and product specification. At the simplest level, it can help maintain a more consistent product and at a complex level, it can improve product quality and performance. Derjaguin, Landau, Vervey, and Overbeek (DLVO) developed a theory of colloidal stability, which currently represents the cornerstone of our understanding of interactions between colloidal particles and their aggregation behavior. This theory is also being used to rationalize forces actingbetween interfaces and to interpret particle deposition to planar substrates. The same theory isalso used to rationalize forces between planar substrates, for example, thin liquid films.


  • Surfactants and self-assembly. Detergents and cleaning

    Introduction to surfactants – basic properties, self-assembly and critical packing parameter (CPP)

    Micelles and critical micelle concentration (CMC)

    Micellization – theories and key parameters

    Surfactants and cleaning (detergency)

    Other applications of surfactants

     

    Abstract

     

    Surfactants are amphiphilic compounds, consisting of a “polar” head (ionic –anionicorcationic- or polar group) and a hydrophobic part.The hydrophobic part is typically a hydrocarbonchain of varying length; it can be also a fluorocarbonor a dimethylsiloxane chain.Surfactants adsorb on liquid–air and oil–waterinterfaces and decrease surface and interfacial tensionsand the corresponding works of adhesion. Thus,they facilitate the cleaning of various surfaces. Importantcharacteristics in surfactant science, and forunderstanding their action in cleaning and otherapplications, include both parameters of the surfactants(CMC, Krafft point, hydrophilic/lipophilic balance)and of the (often aqueous) solution they are in(temperature, salts, co-surfactants, time). We will discussall of these parameters in this lecture.The surfactants can be classified according to thenature of the “head”, i.e. their hydrophilic group(anionic, non-ionic, cationic), oraccording to their applications. Many commercial products contain surfactants.Sodium dodecyl sulfate (SDS) is one of the mostwidely used ionic surfactants, while the most famousnon-ionics are the poly(ethylene oxide)s or polyoxyethylenes.Surfactants have many applications: as importantparts of detergents for cleaning, as emulsifiers, foamingagents or stabilizers for colloidal dispersions, invarious applications in biotechnology and catalysisand as components in many complex products, e.g.paints and coatings as well as in lotions, shampoos,etc. In many cases mixed surfactants are used in commercialproducts.


  • Adsorption in Colloid and Surface Science

    Introduction – universality of adsorption – overview Physisorption and chemisorption

    Langmuir adsorption isotherm

    BET and otheradsorption isotherms

    Surface layer growthmodels

    Metal surface in contact with ions in liquid

    SiO2 surfaces in H2O

     

    Abstract

     

    Solids are complex materials, with inherently highenergy surfaces.Aspontaneous process to decrease thishigh surface energy (in order words to “saturate” theselarge surface forces) is via adsorption. In particular, high surface areas exist inporous materials, like activated carbon, alumina or,the well-known from chemistry laboratories, silicagel. These materials have “huge” surface areas (per g).This quantity is called “specific surface area” of solids,Aspec, and is a characteristic of solid materials. Solidsare complex materials and the form, specific surfacearea, porosity, polarity, surface energy and chemicalhomogeneity, including the number of adsorption sites,are important parameters of the solid surface.Adsorption is a universal phenomenon in colloid andsurface science: We are talking about the adsorption ofhigh molecular weight amphiphilic compounds formonolayer creation, the adsorption of gases on solids,adsorption of surfactants, polymers or proteins (biomolecules).We have adsorption on solid surfaces and/orfrom solutions. There are numerous applications ofadsorption: stabilization, cleaning, heterogeneous catalysisincluding catalytic converters in cars, separationslike drying, surface modification and change ofproperties like foaming or rheological ones. Inparticularfor the gas adsorption we can mention additional applicationssuch as measurement of the surface area ofpowders and other solid surfaces or in heterogeneouscatalysis and novel high surface area materials, e.g. zeolites,which can be used for selective separations (likeremoving pollutants). Many porous materials, e.g. activatedcarbon, alumina, clay minerals, silicagelandzeolites, have veryhigh specific surface areas, which can sometimes behigherthan100m2g–1and,onoccasion,evenhigher than1000m2g–1.


  • Emulsions

    Applications and characterization of emulsions

    Destabilization of emulsions

    Emulsion stability

    Quantitative representation of the steric stabilization

    Temperature-dependency of steric stabilization

    Conditions for good stabilization

    Emulsion design

    PIT – Phase inversion temperature of emulsion based on non-ionic emulsifiers

     

    Abstract

     

    We will start this lecture with some basic definitions and look at some more applications. Then, we will present the most important property of emulsions, the stability, the factors that affect it, and how we can “manipulate” (influence) the stability of emulsions. We will discuss destabilization mechanisms of emulsions and use the HLB factor as a quantitative design tool in emulsion science.

    Emulsions are defined as dispersed systems for whichthe phases are immiscible or partiallymiscible liquids.The emulsions are dispersions of one liquid (oil) inanother, often water (w), and are thus typically classifiedas oil-in-water or water-in-oil emulsions. They arerelatively static systems with rather large droplets(diameter of about 1 μm). The word emulsion comesfrom Latin and means “to milk”. Emulsions are typicallyhighly unstable liquid–liquid systems which willeventually phase separate and require emulsifiers,most often mixed surfactants (or other substances,e.g. synthetic polymers or proteins). In milk, the emulsifieris the protein casein.Indeed emulsions are everywhere and find extensiveapplications in the food, pharmaceutical, andcosmetics industries. Emulsions are highly complexmulticomponent systems containing emulsifiers, surfactants, solubilizers, viscosityconditioners and numerous other compounds. About80% of emulsion preparations in the market are ofoil-in-water type. Owing to the skin feel, both cosmeticoil-in-water and water-in-oil emulsions donot contain more than approximately 30% oil. Butteris a water-in-oil emulsion, where the oil is butterfat.


    • Foams

      Characterization of foams

      Preparation of foams

      Measurements of foam stability

      Destabilization of foams

      Drainage of foam by gravity

      Stabilization of foams

      Changing surface viscosity

       

      Abstract

       

      In short, a foam is a dispersion of a gas in a liquid preparedusing a foaming agent, which in most casesconsists of one or more surfactants. These elegantgas–liquid structures, which appear in numerous productsand processes, can be analysed and manipulatedusing many of the tools that have been introduced inearlier chapters. Foams belong to the topic of thisbook because of the large surfaces involved. In addition,the dimension (thickness) of the thin liquid films(so-called lamellae) present in foams fall, at least inthe later part of the foam lifetime, within the colloidregime, from approximately 1 nm to 1 μm. Therefore,a foam is a system with two dimensions in the macroscopicsize range and one dimension potentially inthe colloidal range.Foams are industrially important in many end-useproducts and also quite often as an undesired sideeffect in various processes. Dead plant material in seawatercan also lead to excessive foaming.