Colloids in water

FIGURE 3.11 Representations of hydrophilic, hydrophobic, and association colloidal particles the hydrophilic colloids are bonnd to water as indicated by the dashed lines. Positively charged counter ions surround negatively charged hydrophobic and association colloidal particles. The micelle of the association colloid may be visnalized as a clnster of organophilic hydrocarbon chains inside a ball with anionic heads attracted to water on the snrface of the ball. 

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It turns out that in solutions of c < 0.1 gL 1 thermosensitive homopolymers, such as PNIPAM, PVCL, and PVME, themselves, form stable colloids in water at elevated temperature in the absence of additives or chemical modification [141-147]. The colloids remain stable upon prolonged heat treatment, without detectable aggregation or precipitation. Also, core-shell particles consisting of PNIPAM and a hydrophobic block are stable not only below but also above the LCST up to 50 °C, when the PNIPAM block is expected to be insoluble [185]. Factors that determine the colloidal stability as defined in Sect. 1.1 do not explain, it seems, their stability. In this review we have compiled a fist of all the reported instances where the formation of stable particles was detected in aqueous solutions of neutral thermosensitive neutral polymers at elevated temperature. We present studies of homopolymers, as well as their copolymers consisting of thermosensitive fragments and ei-... 

Scheme 9.10 Hydrogenation of anisole by reusable surfactant-stabilized lr(0) colloids in water. TEM micrograph and size distribution of Ir(0). (Adapted from [102].)...

Fe(III) can oxidize arsenopyrite about 10 times faster than pyrite and the rates are even more rapid if Acidithiobacillus ferrooxidans is present (Welch et al., 2000, 597 Gleisner and Herbert, 2002, 140 Evangelou, Seta and Holt, 1998, 2084). Scorodite, a product of Reaction 3.52, may form colloids in water and natural organic matter (NOM) could assist in stabilizing the colloids (Buschmann et al., 2006, 6019). 

Suspended solid surfaces (particles or colloids) in waters play a prominent role in controlling the concentration of dissolved trace elements. Most of these elements are eliminated by sedimentation after incorporation on to or into particles, generally by complexation with the surface sites. The most common inorganic particles and colloids are non-clay silicates (quartz, potash feldspar, plagioclase, opaline silica (diatoms)) clays (illite, smectite) carbonates (calcite, dolomite) Fe-Mn oxides (goethite, magnetite) phosphates (apatite) sulfides (mackinawite). Particles and colloids in a water body may be classified as a function of their origin ... 

The most abundant colloids in water (including sea water) are clay minerals (see Section 5.4). These... 

Degueldre C., Baeyens B., Goerlich W., Riga J., Verbist J., and Stadelmann P. (1989) Colloids in water from a subsurface fracture in granitic rock, Grimsel test site. Geochim. Cosmochim. Acta 53, 603 -610. 

Miekeley N., Coutinho de Jesus H, Porto da Siveira C. L., and Degueldre C. (1991) Chemical and Physical Characterization of Suspended Particles and Colloids in Waters from the Osamu Utsumi and Morro de Ferro Analog Study Sites, Poco de Caldas, Brazil. SKB Technical Report 90-18. 

For trivalent metals the influence of humic substances present in diluted seawater is shown by the formation of negatively charged species, which might be attributed to metal-humic substance complexes (especially pronounced for fulvic acid). The presence of humic substances, even at lower concentrations, solubilizes iron. This is partly evident by the formation of the cationic species, which are not found in estuarine or seawater unless humic substances are added. These effects might also be attributed to the stabilization of iron colloids in water rich in humic substances. 

A colloid is a dispersion of particles (about 1 X 10 pm to 1 X 10 pm) of oue substauce iu auother substance. A coUoid is distinguished from a regular solution by the Tyndall effect, which is the scattering of visible light by colloidal particles. Colloids in water are classified as hydrophilic colloids and hydrophobic coUoids. 

Figure 10. High-resolution 29Si NMR spectra of silica colloids in water (a) Si, (b) S2, (c) S3, (d) S4. The different chemical shifts (measured as parts per million with respect to correspond to Si atoms in different...

A solution of organic colloids in water is to be concentrated from 8 to 45 percent solids in a single-effect evaporator. Steam is available at a gauge pressure of... 

Fig. 5.8.1. Power spectrum of laser light scattered from silver chloride colloids in water. The circles are for the actual experimental data. The solid line is the sum of two Lorentzians, one centered at zero frequency, the second one at 1.97 kHz. The half-width of the first Loren-tzian is 0.35 kHz and that of the second, 0.29 kHz. The instrumental width is 50 Hz. (From Ben-Yosef et al., 1972.)...

Amphotericin B is complexed with deoxycholate (C-AMB) and marketed as a lyophilized powder (fungizone) containing 50 mg of amphotericin B that forms a colloid in water. Three lipid formulations of amphotericin B are marketed in the U.S. Amphotericin B colloidal dispersion (ABCD, AMPHOTEC, amphocil) contains equimolar amounts of amphotericin B and cholesteryl sulfate. AMBISOME is a small, unilamellar vesicle formulation that combines amphotericin B (50 mg) with 350 mg of lipid (phosphatidylcholine, cholesterol, and distearoylphosphatidylglycerol, in molar ratio of 10 5 4) in an -10% molar ratio. Amphotericin B lipid complex (ABLC, abelcet) contains dimyristoylphosphatidylcholine and dimyristoylphosphatidylglycerol in a 7 3 mixture with -35 mol% of amphotericin B. 

Oxides, especially those of silicon, aluminum, and iron, are abundant components of the earth s crust they participate in geochemical reactions and in many chemical processes in natural waters, and often occur as colloids in water and waste treatment systems. The properties of the phase boundary between a hydrous oxide surface and an electrolyte solution depend on the forces operating on ions and water molecules by the solid surface and on those of the electrolyte upon the solid surface. The presence of an electric charge on the surface of particles often is essential for their existence as colloids the electric double layer on their surface hinders the attachment of colloidal particles to each other, to other surfaces, and to filter grains. 

Stability is improved by protective colloids, which are polymeric materials with highly polar and non-polar features in their molecular structures. They provide additional steric stabilization. If the protective colloids are not truly compatible with the film-former, gloss will be reduced and the film weakened. Frequently the colloids in water paints (e.g. water-soluble cellulose derivatives) are affected by microorganisms, so fungicides and bactericides may be included to prevent deterioration. 

GO possesses a single layered two-dimensional sp hybrid structure with sufficient hydrophilic surface groups and therefore forms stable colloids in water. But under physiological buffers, GO aggregates due to the presence of salts, which has a charge screening effect [84]. 

A Figure 13.30 Schematic illustration of the stabiiization of a hydrophobic colloid in water by adsorbed ions. 

Gold is bright yellow but finely divided it is black like other metal powders. Suspended as a colloid in water the color ranges from ruby red to purple. 

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