Colloids, reversible

Proteins and colloids Reversible adsorbed layer Transition from reversible to irreversible fouling... 

Colloid, reversible n. Colloid substance that can be converted from the gel to the solid form without the expenditure of chemical energy, that is, by simply warming the gel form or redissolving the dried substance in water. It is a colloid which forms a hydrophilic solid, such as gelatin, agar, gum arabi, starch a protective colloid. 

T.W. Healy, A. Homola, R.O. James, R.J. Hunter, Coagulation of amphoteric latex colloids reversibility and specific ion effects. Faraday Discuss. Chem. Soc. 65, 156-163 (1978). doi 10. 1039/dc9786500156... 

The statement so often met with in the literature that the precipitation of these finer suspensions is irreversible, as in the case of colloidal metals, is quite false. Schlosing has demonstrated that after the removal of the electrolyte the clay may be returned to its original suspended form. In this regard turbid clay solutions resemble hydro-phile colloids (reversible) much more than they do metal hydrosols, and from the properties of the precipitate should be classed with the former rather than with the latter. The similarity between turbid solutions of clay and metal hydrosols exists almost exclusively in the sensitivity of both toward electrolytes. This sensitivity, however, they have in common with certain ionogen disperse solutions such as Congo-red and Benzo-purple. 

Hasegawa M, Sugimura T, Shindo Y and Kitahara A 1996 Structure and properties of AOT reversed micelles as studied by the fluorescence probe technique Colloids Surf. A 109 305-18... 

Overbeek, J. Th., 1949. Reversible systems. In Colloid Science, Vol. 2. Ed. H.R. Kruyt. Amsterdam Elsevier. 

The most important application of semi-permeable membranes is in separations based on reverse osmosis. These membranes generally have pores smaller than 1 nm. The pressure across the semi-permeable membranes for reverse osmosis is generally much larger than those for ultrafiltration, for example. This is because reverse osmosis is usually used for small molecules which have a much higher osmotic pressure, because of the higher number density, than the colloids separated in ultrafiltration. As a result reverse osmosis membranes have to be much more robust than ultrafiltration membranes. Since the focus of our discussion in this chapter will be on reverse osmosis based separations, we will describe these membranes in greater detail. 

Ionic silica is not totally removable by DI. Colloidal silica is difficult to remove by both DI and reverse osmosis (RO) it may cause some resin fouling as well as leaking into the treated water. Where the cation effluent is maintained at a pH of 2.0 to 3.0, however, silica tends to both depolymerize and ionize thus enabling its effective removal in strongly basic, anion resin beds. 

Figure 51. Arrhenius plot of ln 1/(3 [ Q t)ldt2]) from data corresponding to Fig. 54. The conformational energy consumed per mole of polymeric segments in the absence of any external electric field (AH) can be obtained from the slope. (Reprinted from T. F. Otero and H.-J. Grande, Reversible 2D to 3D electrode transition in polypyrrole films. Colloid Surf. A. 134, 85, 1998, Figs. 4-9. Copyright 1998. Reproduced with kind permission of Elsevier Science-NL, Sara Burgerhartstraat 25, 1055 Amsterdam, The Netherlands.)...

The next two chapters concern nanostructured core particles. Chapter 13 provides examples of nano-fabrication of cored colloidal particles and hollow capsules. These systems and the synthetic methods used to prepare them are exceptionally adaptable for applications in physical and biological fields. Chapter 14, discusses reversed micelles from the theoretical viewpoint, as well as their use as nano-hosts for solvents and drugs and as carriers and reactors. 

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