Surface Chemistry: Coagulation Physical and chemical processes to induce collisions and growth of particles, and to remove some soluble contaminants: Coagulation: Formally, means making particles “sticky” (rapid mix step); colloquially, also refers to forming new particles that collect dissolved contaminants Flocculation: Collisions among sticky particles (slow mix step), to converge and form fewer, larger and … Read more
Surface Chemistry: Electrophoresis Electrophoresis means “to carry with electricity”. It is a method where charged molecules in solution, migrate in response to an electrical field. Their rate of migration through the electrical field, depends on the strength, net charge, size, and shape of the molecules, along with the ionic strength, viscosity, and temperature of the … Read more
Surface Chemistry: Brownian movement One of the first pieces of evidence for how gases move was discovered by Robert Brown a botanist who noticed that pollen grains in the water moved about randomly. Robert Brown noticed that small grains of pollen (Clarkia) suspended in water, moved in a haphazard or random fashion. In 1905, Einstein … Read more
Surface Chemistry: Tyndall effect A beam of sunlight is not visible to the naked eye unless the light passes through particles of water (mist) or dust in the air. These particles are responsible to scatter the sunlight and show its direction of penetration. Similarly, the light becomes is visible as it passes through a colloid. … Read more
Surface Chemistry: Properties of Colloids Due to their small size, colloidal particles do not settle out of solution. Particles lying in the colloidal size range possess an enormous surface area compared with the surface area of an equal volume of larger particles. In order to compare the surface area of different systems, we use the … Read more
Surface Chemistry: Lyophobic, multimolecular and macromolecular colloids Two phases are involved in a colloidal system Dispersed phase – solid, liquid, gas Dispersion medium (continuous phase) — solid, liquid, gas General types of colloidal system: Lyophobic colloids are solvent hating colloids(Lyo means solvent and phobic means hating). There is minimal or no affinity between particles … Read more
Surface Chemistry: Lyophilic colloids The nature of interactions between a dispersed phase and dispersion medium directs the colloidal solutions to be classified into two types as lyophilic and lyophobic sols. Lyophilic colloids aresolvent loving(Lyo means solvent and philic means loving). These are the colloidal solutions, in which the particles of the dispersed phase have a … Read more
Surface Chemistry: Enzyme catalysis and colloidal state Enzymes are extremely effective biologically active catalysts. They are homogeneous catalysts, reacting in solution with body fluids. Only one type of molecule selectively fits the active site in its “lock and key” mechanism. Therefore, enzymes are very specific as to what they catalyse on a specific substrate. Enzymes … Read more
Surface Chemistry: Homogenous and heterogeneous catalysis Activity and Selectivity Activity is the ability of the catalyst to accelerate a chemical reaction. The degree can be as high as 100 times in certain reactions. A catalytic cycle processes in which the reactant and catalyst undergo several transformations before making the products. A catalyst should regenerate after … Read more
Surface Chemistry: Catalysis According to the collision theory, particles need to have at least a minimum amount of activation energy to initiate the reaction. Catalysis is a process in which a catalyst is used to reduce the activation energy of a reaction by changing the path of the reactants. It is the manifestation, study, and … Read more