Retardation colloids

The electrolysis protection process using impressed current aluminum anodes allows uncoated and hot-dipped galvanized ferrous materials in domestic installations to be protected from corrosion. If impressed current aluminum anodes are installed in water tanks, the pipework is protected by the formation of a film without affecting the potability of the water. With domestic galvanized steel pipes, a marked retardation of the cathodic partial reaction occurs [15]. Electrolytic treatment alters the electrolytic characteristics of the water, as well as internal cathodic protection of the tank and its inserts (e.g., heating elements). The pipe protection relies on colloidal chemical processes and is applied only to new installations and not to old ones already attacked by corrosion. 

An important aspect of semiconductor photochemistry is the retardation of the electron-hole recombination process through charge carrier trapping. Such phenomena are common in colloidal semiconductor particles and can greatly influence surface corrosion processes occurring particularly in small band gap materials, such... 

Although it presents an obstacle in practical applications, the photoanodic corrosion of colloids has often been used to obtain information about the interaction of dissolved compounds with the photo-produced charge carriers, as it was found that solutes can influence the rate of the dissolution. Both promoting and retarding effects were observed The rate of dissolution is readily followed by recording the decrease in the intensity of the absorption spectrum of the colloid upon illumination, or more precisely, by determining the yields of metal and sulfate ions in solution. 

A further improvement in flame-retardant efficiency is observed when a colloidal dispersion of tin(IV) oxide is incorporated into the polyester. At a 1.5% addition level, colloidal SnO gives an 01 value (49.0) which is markedly higher than that obtained with 5% loadings of either anhydrous SnO, (47.7) or 8-stannic acid (47.9), as powdered additives (Figure 2). In addition to its increased flame-retardant ability, colloidal Sn02 offers the further advantages of translucency in the cured plastic, ease of incorporation and nonsettling in the resin prior to cure. 

The surface area and degree of dispersion in the polymer matrix of the fire-retardant additive has a pronounced effect on its efficiency. Colloidal tin(IV) oxide is significantly more effective, in terms of its flame-retardant ability, than powdered tin(IV) oxide or B-stannic acid. 

Iodine, most ancient of the therapeutic agents for thyroid disorders, inhibits the secretion of thyroid hormone by retarding both the pinocyto-sis of colloid and proteolysis. This effect is observed in euthyroid as well as hyper thyroid persons. 

Condensed-phase flame retardant mechanisms, 44 484—485 Condensed phosphates, 18 841-852 colloidal properties of, 48 851 complex ion formation in,... 

It is reasonable to expect that because anions and most colloidal particles in temperate region soils have a negative charge, they will repel each other. The consequence is that anions will pass through soil and will not be adsorbed or even retarded. For the simple anions and some of the oxyanions, this is exactly what happens. All the halides, nitrite, nitrate, bicarbonate, and carbonate act in this fashion. However, there are some oxyanions that do not act as expected, and chief among them is phosphate. 

Now, because the water-borne radioactive element is predominantly associated with the colloids, we no longer have a need for the distribution coefficient. There will still be a partitioning because the major portion of the radioactive elements will still be adsorbed to the sediment. This is a separate equilibrium partitioning coefficient, requiring a new experiment on the clay sediments and the colloids present. The partitioning colloid-clay ratio would most likely be dependent on the surface areas of each present in the sediments. A separate size distribution analysis has resulted in a sediment-colloid surface area ratio of 99 1 for the sediment. This results in a colloid retardation coefficient oiRc = 100 rather than Ri = 4.2 x 10 or i 2 = 6 x 10. ... 

The reliable long-term safety assessment of a nuclear waste repository requires the quantification of all processes that may affect the isolation of the nuclear waste from the biosphere. The colloid-mediated radionuclide migration is discussed as a possible pathway for radionuclide release. As soon as groundwater has access to the nuclear waste, a complicated interactive network of physical and chemical reactions is initiated, and may lead to (1) radionuclide mobilization (2) radionuclide retardation by surface sorption and co-precipitation reactions and (3) radionuclide immobilization by mineralization reactions, that is, the inclusion of radionuclides into thermodynamically or kinetically stabilized solid host matrices. 

Under given conditions, colloids do not have an impact on the migration of Sr(II), U(VI) and Np(V), which display only weak or no interaction with the colloids. While Sr(II) migrates as a weak sorbing tracer, the oxidized actinides U(VI) and Np(V) are partly eluted together with the conservative tracer, that is, without retardation. A second part of U(VI) and Np(V) appears slightly retarded probably due to the weak reversible interaction with surfaces of the fracture infill. 

Mori, A., Alexander, W. R. et al. 2003. The colloid and radionuclide retardation experiment at the grimsel test site Influence of bentonite colloids on radionuclide migration in a fractured rock. Colloids Surfaces, 217, 33-47. 

Foam properties related to salt. The addition of sodium chloride to soybean protein suspensions caused them to form high-capacity, low-stability foams (13). It was suggested that foam capacity increased because salt improved protein solubility at the interface of the colloidal suspension during foam formation, but retarded the partial denaturation of the surface polypeptides of proteins that are necessary for protein-protein interaction and stability. 

---