Iron silicate colloid

The results of additional experiments conducted with 85Sr and 137Cs spikes are shown in Figure 4. The well known sorption characteristics of bentonite for Sr and Cs ions is apparent (7). The sorption properties of bentonite are reduced at low pH, which is consistent with an electrostatic concept. 137Cs sorption on the iron silicate colloids is considerably less than that observed with bentonite, even though the colloid zeta potentials are similar, which suggests that mechanisms other than simple electrostatic concepts may be involved. Also, the linear trend of data for Sr in iron silicate systems is considered to represent precipitation rather than sorption. 

Actinide and Technetium Sorption on Iron-Silicate and Dispersed Clay Colloids... 

Figure 1. Sorption of 237Pu and 233U by Iron Silicate (top) and Na Bentonite (bottom) Colloids at 25°C.

Figure 3. Sorption of 95mTc and 235Np on Iron Silicate and Na-Bentonite Colloids at 25°C and Comparison with Possible Tc and Np Speciation.

Figure 4. Sorption of 137Cs and 85Sr by Colloidal Iron Silicates and Na Bentonite at 25°C.

Silt density index measures suspended solids, particularly colloids, such as alumina- or iron silicates, clay, iron corrosion products, and microbes, that have a great potential for fouling RO membranes (see Chapter 3.8 for more details about SDI). The SDI should be as low as possible to minimize fouling of the membranes, but must be less than 5 to meet warranty requirements set by the membrane manufacturers (best practices call for SDI in RO feed water to be less than 3). Note that there is no direct correlation of turbidity to SDI, other than high turbidity usually means high SDI (the converse is not always true). 

EC is effective in water treatment for drinking water supply, membrane pre-treatment, marine operation, and boiler water supply for small systems. It is very effective in treating colloids found in natural water by reducing turbidity and colour as well as removing suspended solids, oil and grease, iron, silicates, humus and microorganisms. A comprehensive summary of pollutants removed by EC is given in [24]. 

As pointed out by Sposito (1984) this equation initiated the surface chemistry of naturally occurring solids. Maarten van Bemmelen published this equation (now referred to as the Freundlich isotherm) more than 100 years ago and distilled from his results, that the adsorptive power of ordinary soils depends on the colloidal silicates, humus, silica, and iron oxides they contain. 

The Oxide Ores (e.g., ores of iron, chromium, manganese, tin).— The study of these ores involves high-temperature investigations similar to those on the silicates, and also studies of the hydrated and colloidal oxides. 

The preparation of lyophilic sols is easy and most of the time a mixture of the dispersion medium and the substance to be dispersed need only be stirred. Gelatine, for example, disperses almost spontaneously in water. The hydroxides of iron, aluminium, chromium and zirconium as well as vanadium pentoxide and silicic acids all belong to the group of hydrophilic colloids. 

The effectiveness of zerovalent iron in removing arsenic from water also greatly depends on the properties of the iron. As(III) removal is especially effective with high surface area 1-120 nm spheres of zerovalent iron (Kanel et al., 2005). Provided that interfering anions (such as, carbonate, silicate, and phosphate) are insignificant, colloidal spheres of zerovalent iron could be injected into arsenic-contaminated soils, sediments, and aquifers for possible in situ remediation (Kanel et al., 2005, 1291). 

Clay minerals and clay colloids are the products of the advanced weathering of primary silicates. They are comprised mainly of silica and alumina, often with appreciable amounts of alkali and alkaline earth metals and iron. Most also have varying amounts of water bound to their surfaces and can take on a variety of different chemical and physical properties depending on the amount of water adsorbed. They have the ability to exchange or bind cations and anions and are capable of complex formation with a wide variety of organic molecules. 

---