Sorption onto Colloidal Particles

A series of experiments was also conducted by Bowman et al. [34] to ascertain the effects of differing environmental factors on the sediment-water interactions of natural estrogens (estradiol and estrone) under estuarine conditions. Sorption onto sediment particles was in this case relatively slow, with sorption equilibrium being reached in about 10 and 170 h for estrone and estradiol, respectively. On the other hand, true partition coefficients calculated on colloids were found to be around two orders of magnitude greater that those on sediment particles. Hence, it was concluded that under estuarine conditions, and in comparison to other more hydrophobic compounds, both estrone and estradiol... 

A characteristic feature of these mixtures consists in selection of individual components, whose pH of precipitation promotes increasing the size of colloid particles in co-precipitation of hydroxides. In order to satisfy this condition it is necessary that pH of initial precipitation of hydroxides in the mixture do not coincide and that the component composition of the samples differ at the sorption maximum. Moreover, the use of other compositions of binary systems cannot be excluded. However, in this case the highest structure forming effect is not achieved. In spite of the fact that such systems are multicomponent, the mechanism of forming porosity is almost the same as the mechanism of structure formation in binary mixtures [13,15]. The difference only consists in the number of built-up components and the order of their deposition onto colloid particles precipitated first. 

These findings indicate that even though the lime stabilization process of the biosolid waste may contribute to increased immobilization of soluble metals by sorption or precipitation onto the solid phase, in retrospect, it could create conditions favorable for increased dispersion and mobility of colloid particles and their metal load. 

World-wide activities focus on the remediation of radioactively contaminated sites. Part of such efforts were projects funded by the DFG (Deutsche Forschungsgemein-schaft) Characterization of colloidal particles in drainage systems of abandoned Sax-onian mines and Investigation of mechanisms of uranium(VI) sorption onto rock and mineral surfaces. Identification and modelling of sorbed surface species on a molecular level and funded by the EC Restoration Strategies for radioactively contaminated sites and their close surroimdings . One common aim was to deliver a more pro-... 

The values of kj calculated by Bacon and Anderson (1982), and used in most models of Th scavenging, varied with particle concentration and ranged from 0.2 to 1.2 Such values are appreciably longer than expected from sorption rates onto particle surfaces. The discrepancy can be explained if dissolved Th is initially sorbed to surfaces of very small particles (colloids) that pass through the typical filters (0.1-0.4 im) used to separate dissolved from particulate fractions (Santschi et al. 1986). 

There have been several laboratory and field studies concerned with the uptake of aqueous plutonium by plants, marine biota, soils, minerals, and glass. These have been discussed in the first paper of this series (I), which shows that several solution variables, as they influence the particle size distribution of the aqueous plutonium, greatly affect its interaction with silica surfaces. Studies were conducted to determine the rates, equilibria, and mechanism of the sorption and desorption of aqueous, colloidal plutonium-239 onto the surfaces of quartz silica. The orientation of these studies is the understanding of the likely behavior and fate of plutonium in environmental waters, particularly as related to its interaction with suspended and bottom sediments. 

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