Solid colloid systems

Chem. Descrip. Anionic, high solids, colloidal system containing a low-modulus polychloroprene homopolymer CAS 9010-98-4... 

Under favourable conditions these additional phases may be reali2 ed as a homogeneous liquid macro layer or as distinct crystal individuals. The designation phases for these liquid or solid colloid systems is justified because each of them represents a... 

Solid colloidal systems like ruby glass (which may be considered as a solidified colloidal suspension of individual gold particles in molten glass) or like a solid foam are excluded by this definition. 

Among the solid colloid systems can first of all be incxaded those systems of which the dispersion medium is solid such as ruby glass (colloidal dispersion of gold in glass). 

Attempts have often been made to represent the behaviour of solid colloid systems on deformation by mechanical models, which consist of a combination of elastic and viscous elements. The elastic elements arc represented by springs and the viscous by dashpots, the motion of which is retarded by a viscous liquid. Since in actual systems one is also always dealing with a combination of elastic elements (by which potential energy can be stored) and of internal frictional resistances (in which energy is dissipated) the analogy is more than a formal one. One can indeed often make a useful picture of the deformation mechanism by the construction of such models. 

Many colloid systems are random dispersions, in which no double refraction is indeed to be expected With a number of solid colloid systems this is otherwise and orientation double refraction can appear in various forms We shall return to this presently Frequently the case occurs that a non-double refracting system can be made anisotropic by certain constraints Just this double refraction under strain has become an important research method for colloid systems which can give valuable information on the structure of the system ... 

Macromolecular substances above their melting point are of course to be considered as liquid colloid systems which, when the temperature faUs below the setting point, set and are then transformed into solid colloid systems This transition does not differ from that in other congealing substances of low molecular weight Reference can therefore be made to textbooks where such transitions are discussed ... 

Typically RO systems are preceded by pretreatment units to remove suspended solids/colloidal matter and add chemicals that control biological growth and reduce scaling. Membranes are typically made of synthetic polymers coated on a backing (skin). Examples of membrane materials include polyamides, cellulose acetate and sulfonated polysulfone. 

The invasion of particles can be eliminated either by using solids-free systems or by formation of a competent filter cake on the rock surface. If the components forming the filter cake are correctly chosen and blended, they will form a very effective downhole filter element. This ensures that colloidal sized clays or polymeric materials are retained within the filter cake and do not enter the formation. Further protection is provided by ensuring that a thin filter cake is formed due to low dynamic and static filtrate losses. Thus, the cake may be easily removed when the well is brought into production. Additionally, the filter cake can be soluble in acid or oil. 

SO sharply defined that they are called surfaces. Well-defined surfaces occur between solids and either gases or liquids and thus are commonly found in catalytic and electrode reactions. More diffuse interfaces may occur between solids, as in microelectronic devices, and between fluids or semifluids, as in many polymeric and colloidal systems. 

While the nuclear magnetic resonance (NMR) technique has widely been used to study diffusion processes of normal liquids, solids, or colloidal systems, there are only a few applications to molten salts. The spin echo self-diffusion method with pulsed field gradients was applied to molten salts by Herdlicka et al. "" There is no need to set up or maintain a concentration gradient. 

Foams are agglomerations of gas bubbles separated from each other by thin films (5). Mainly, the problem is concerned with one class of colloidal systems —gas dispersed in liquid—but liquid dispersed in gas, solids dispersed in liquid (suspensions), and liquids dispersed in liquids (emulsions) cannot be ignored. The dispersion of a gas into a liquid must be studied and observed by the food technologist to improve the contact between the liquid and gas phases, the agitation of the liquid phase, and most important, the production of foam 10). 

The electrokinetic processes can actually be observed only when one of the phases is highly disperse (i.e., with electrolyte in the fine capillaries of a porous solid in the cases of electroosmosis and streaming potentials), with finely divided particles in the cases of electrophoresis and sedimentation potentials (we are concerned here with degrees of dispersion where the particles retain the properties of an individual phase, not of particles molecularly dispersed, such as individual molecules or ions). These processes are of great importance in particular for colloidal systems. 

RC Oppenheim. Solid colloidal drug delivery systems nanoparticles. Int J Pharm 8 217-234, 1981. 

Ionic (electrolytic) conduction of electric current is exhibited by electrolyte solutions, melts, solid electrolytes, colloidal systems and ionized gases. Their conductivity is small compared to that of metal conductors and increases with increasing temperature, as the resistance of a viscous medium acts against ion movement and decreases with increasing temperature. 

The interfacial properties of chain-like molecules in many polymeric and colloidal systems are dependent on the conformation of the chains adsorbed at the interface (.1). Chains adsorbed at the solid-liquid interface may be produced by anchoring diblock copolymers to particles in a polymer dispersion. Such dispersions are conveniently prepared by polymerizing in the presence of a preformed AB diblock copolymer a monomer dissolved in a diluent which is a precipitant for the polymer. The A block which is... 

Not all colloid systems are stable. The most stable involve solid dispersion media, since movement through a solid host will be slow. Emulsions also tend to be stable think, for example, about a glass of milk, which is more likely to decompose than undergo the destructive process of phase separation. Aerosols are not very stable although a water-based polish generates a liquid-in-air colloid, the particles of liquid soon descend through the air to form a pool of liquid on the table top. Smoke and other solid-in-gas aerosols are never permanent owing to differences in density between air and the dispersed phase. 

Endocytosis is an ubiquitous system for engulfing solid/colloidal materials by cells by encapsulating them in membrane-bound vesicles. 

Colloidal systems were reported to be much more effective than immobilized or supported catalysts for photodegradation of ary hazardous molecule [72,73], Powdered materials exhibit an important inconvenience. The main difficulty in employing an insoluble, powdered semiconductor in aqueous dispersion is the need to remove the solids after treatment and subsequent redispersion in a second aqueous solution to be purified. However, in the case of colloids it was speculated that they may either be dispersed in the irradiated aqueous solution as a colloidal suspension, or attached to a suitable support as a fixed or mobile fluidized bed [72,73],... 

The main objectives of the present chapter are to (1) discuss in detail the compositions of the different solid phase systems covered in this volume which include soils, sediments, suspended matter, colloids, and biocolloids/biosolids, (2) review the various interaction mechanisms between organic pollutants and... 

Before discussing the various interaction mechanisms between organic pollutants and solid phase systems, it is important to describe briefly the compositions of such solids mentioned in this chapter and throughout the volume. This can provide insight about the possible interaction mechanisms and their mode of chemical interactions. These phases include soils, sediments, suspended solids, colloids, and biocolloids (i. e., biosolids). 

The humic/organic matter coatings of different solid phases (i. e., SPm /SP0M), such as soils, sediments, suspended solids, colloids, and biocolloids/biosolids, interact with organic pollutants in aqueous systems in various ways. Adsorption is an important interaction mode. The reversibility and/or irreversibility of the adsorption processes is of major importance. The question whether the bound residues of pollutants are to be considered definitely inactivated has been the focus of extensive research. This question was posed as follows. Have the adsorbed pollutants become common components incorporated into the humic polymer coating of solid phases (i. e., being absorbed), or are they only momentarily inactivated in reversibly bound forms thus representing a possible source of pollution by a time-delayed release of toxic units ... 

Various diverse systems qualify as gels if one assumes that in these systems the common features are the solid-like behavior and the presence of a continuous structure of macroscopic nature (6,7). For the purpose of the discussion in this paper, we describe a gel as a colloidal system comprised of a dispersed component and a dispersion medium both of which the junction points are formed by covalent bonds, secondary valence bonds, or long range attractive forces that cause association between segments of polymer chains or formation of crystalline regions which have essentially infinite life time (8). 

We need to understand under which conditions a colloidal system will remain dispersed (and under which it will become unstable). Knowing how colloidal particles interact with one another makes possible an appreciation of the experimental results for phase transitions in such systems as found in various industrial processes. It is also necessary to know under which conditions a given dispersion will become unstable (coagulation). For example, one needs to apply coagulation in wastewater treatment so that most of the solid particles in suspension can be removed. Any two particles coming close to each other, will produce different forces. 

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