Colloidal matter

Polymeric flocculants are available in various chemical compositions and molecular weight ranges, and they may be nonionic in character or may have predominantly cationic or anionic charges. The range of application varies but, in general, nonionics are well suited to acidic suspensions, anionic flocculants work well in neutral or alkaline environments, and cationics are most effective on organic material and colloidal matter. 

Major problems inherent in general applications of RO systems have to do with (1) the presence of particulate and colloidal matter in feed water, (2) precipitation of soluble salts, and (3) physical and chemical makeup of the feed water. All RO membranes can become clogged, some more readily than others. This problem is most severe for spiral-wound and hollow-fiber modules, especially when submicron and colloidal particles enter the unit (larger particulate matter can be easily removed by standard filtration methods). A similar problem is the occurrence of concentration-polarization, previously discussed for ED processes. Concentration-polarization is caused by an accumulation of solute on or near the membrane surface and results in lower flux and reduced salt rejection. 

Typically RO systems are preceded by pretreatment units to remove suspended solids/colloidal matter and add chemicals that control biological growth and reduce scaling. Membranes are typically made of synthetic polymers coated on a backing (skin). Examples of membrane materials include polyamides, cellulose acetate and sulfonated polysulfone. 

Removal of particulates, colloidal matter, iron and organics. Multimedia, manganese, greensand, diatomaceous earth, brim, or carbon filter. Caution carbon filters not recommended unless absolutely required for the removal of color and odor (as they provide a medium for microbial growth). 

Soils are commonly named and classified according to the general size range of their particulate matter. Thus sandy, sih and clay types dwive their names from the predominant size range.of inorganic cons tiiuents. Particles between 0 07 and about 2 mm are classed as sands. SUt particles range from 0-005 mm to 0-07, and clay particle Size ranges from 0-005 mni mean diameter down to colloidal matter. 

Microelectrophoresis (electrophoretic mobility) . This involves the measurement of particle charge in an applied field. For paper furnishes, the supernatant solution—which contains finely divided colloidal matter, is usually removed and used to conduct the measurement. It must be questioned therefore as to how reflective this is of the charge characteristics of the larger particles and fibres which settle. However, as it is the colloidal fraction which requires to be flocculated to assist retention during drainage, it is still a useful measurement. 

Coagulants are used to bind together particulate and colloidal matter so they may be filtered from the feed before the membrane process. Coagulants can be either inorganic (such as ferric salts) or organic polyelectrolytes. The correct dosage and... 

In Curie-point Py-LVMS studies of maceral concentrates (22). vitrinitic moieties were shown to be the main source of the hydroxy aromatic components. Thus, the hydroxy aromatic signals observed in Figure 2d appear to be primarily derived from vitrinite-like components by means of pyrolytic processes. Presumably, therefore, the "nonmobile phase", rather than the "mobile phase , is the main source of the phenols observed in TG/MS and Py-MS studies of Pittsburgh 8 coal (9,16). Further support for this conjecture comes from the observation that phenolic products are also observed in Py-MS analysis of pyridine extracts of Pittsburgh 8 coal known to contain colloidal matter whereas the corresponding tetrahydrofuran extracts, free of colloidal material, produced no phenols (21). 

Reverse osmosis performs a separation without a phase change. Thus, the energy requirements are low. Typical energy consumption is 6 to 7 kWh/m2 of product water in seawater desalination. Reverse osmosis, of course, is not only used in desalination, but also for producing high-pressure boiler feedwater, bacteria-free water, and ultrapure water for rinsing electronic components—because of its properties for rejecting colloidal matter, particle and bacteria. 

In the (aquatic) environment elements occur in particulate-, colloidal- and dissolved forms. These forms are usually distinguished by filtration or centrifugation. Traditionally, a 0.45 um (membrane)- filter separates the particulate from the dissolved forms. This may result in the passage of colloidal fractions through the filter, classifying colloidal matter incorrectly within the dissolved fraction. Although the interaction between dissolved and particulate (surface) fractions cannot be neglected, it is common in speciation studies to consider the "dissolved" fraction. The dissolved forms of trace elements are mainly present as ... 

No attempt was made to reduce the ash content of the humic acid samples, since drastic purification methods can cause abnormal changes in humate characteristics, and it was believed that most organic acids in their natural environment would be in salt form and associated with other colloidal matter. Though competition from displaced cations may have contributed to the smaller uptake by humic acid (HA II) in the adsorption stage (as shown in Table 2.1), any residual counterions should have had little effect on the metal-ion extraction step. 

Means, J. C., and R. D. Wijayaratne. 1984. Chemical characterization of estuarine colloidal matter implications for adsorptive processes. Bulletin of Marine Science 35 449. 

Applicable to unpolluted samples with a low content of organic matter. Samples should be filtered to avoid interference from suspended particles or colloidal matter and organic compounds. Several ions (Br-, SCN-, I-, COf-, N02, Fe2+, Fe3+, and Cr(VI)) may be important interferents... 

The importance of colloidal complexation clearly varies with the trace metal in question. For example, most of the Fe in rivers may be in colloidal form, which is critical in the coagulation/aggregation removal processes of Fe in estuaries (Millward and Turner, 1995). On the other hand, Cd and Ni have a low affinity for colloidal matter (Dai et al., 1995). In the Ochlocknee estuary (USA), Fe and Mn behaved nonconservatively and... 

Tarr, M.A., Wang, W., Bianchi, T.S., and Engelhaupt, E. (2001) Mechanisms of ammonia and amino acid photoproduction from aquatic humic and colloidal matter. Wat. Res. 35, 3688-3696. 

---