Colloidal material

Table 3. Industrially Produced Colloidal Materials and Related Processes...

Table 6. Exposure Limits of Selected Colloidal Materials ...

Among the methods of foam separation, foam fractionation usually implies the removal of dissolved (or sometimes colloidal) material. The overflowing foam, after collapse, is called thefoamate. The solid lines of Fig. 22-42 illustrate simple continuous foam fractionation. (Batch operation would be represented by omitting the feed and bottoms streams.)... 

Pretreatment For most membrane applications, particularly for RO and NF, pretreatment of the feed is essential. If pretreatment is inadequate, success will be transient. For most applications, pretreatment is location specific. Well water is easier to treat than surface water and that is particularly true for sea wells. A reducing (anaerobic) environment is preferred. If heavy metals are present in the feed even in small amounts, they may catalyze membrane degradation. If surface sources are treated, chlorination followed by thorough dechlorination is required for high-performance membranes [Riley in Baker et al., op. cit., p. 5-29]. It is normal to adjust pH and add antisealants to prevent deposition of carbonates and siillates on the membrane. Iron can be a major problem, and equipment selection to avoid iron contamination is required. Freshly precipitated iron oxide fouls membranes and reqiiires an expensive cleaning procedure to remove. Humic acid is another foulant, and if it is present, conventional flocculation and filtration are normally used to remove it. The same treatment is appropriate for other colloidal materials. Ultrafiltration or microfiltration are excellent pretreatments, but in general they are... 

Grier, D.G. (ed.) (1998, Oetober) Directed self-assembly of colloidal materials, MRS Bull. 23(10), 21. 

RO membrane performance in the utility industry is a function of two major factors the membrane material and the configuration of the membrane module. Most utility applications use either spiral-wound or hollow-fiber elements. Hollow-fiber elements are particularly prone to fouling and, once fouled, are hard to clean. Thus, applications that employ these fibers require a great deal of pretreatment to remove all suspended and colloidal material in the feed stream. Spiral-wound modules (refer to Figure 50), due to their relative resistance to fouling, have a broader range of applications. A major advantage of the hollow-fiber modules, however, is the fact that they can pack 5000 ft of surface area in a 1 ft volume, while a spiral wound module can only contain 300 ftVff. 

Flocculation Agglomeration of colloidal material by adding a chemical that causes the colloidal particles to produce larger particles. 

Suppose we have a physical system with small rigid particles immersed in an atomic solvent. We assume that the densities of the solvent and the colloid material are roughly equal. Then the particles will not settle to the bottom of their container due to gravity. As theorists, we have to model the interactions present in the system. The obvious interaction is the excluded-volume effect caused by the finite volume of the particles. Experimental realizations are suspensions of sterically stabilized PMMA particles, (Fig. 4). Formally, the interaction potential can be written as... 

Cake build up-ttih hole. Differential alieklng (wall eticklng). Add colloidal material to reduce cakt thlcknaas. Add suKactanta... 

High filuaiion rate. Add colloidal material to reduce filtrate loss. 

HARD ROCK (Sebtot. Isneou, u.) Ttanaportatlon ot cuttJnga inercaw viscoelty and gelt by addition ot colloidal materials. 

Process leaks of sugars, fats, colloidal materials, pectins, emulsions, and proteins cause stable foams in the boiler, leading to carryover and a further contamination cycle. 

Process leaks from food and beverage production or wood leachates often produce sugars, colloidal materials, pectins, emulsions, and proteins that cause stable foams in the boiler. These lead to carryover and further steam-condensate line contamination. The temporary use of a demulsifier or defoamer as part of the water treatment program may be of particular benefit, but again the condensate is unsuitable for return to the boiler. Other process leaks include ... 

Most raw water sources considered for use as boiler MU have been treated or conditioned either by a water utility (providing city water) or in-house (providing industrial water). They are supplied to the boiler plant clean and relatively free of suspended solids, colloidal material, organics, and iron. In hard water areas there also may be some reduction in hardness and alkalinity provided. Where boiler plant raw water (RW) quality is still unacceptable for the particular boiler plant needs, additional pretreatment pre-boiler conditioning or external treatment) may be required. 

In addition, even where foaming is not a specific problem in a boiler, carryover may occur, especially in lower pressure boilers with very high TDS (i.e., over 10,000 to 15,000 ppm TDS) because of the collapse of surface bubbles. This leads to BW aerosol generation and entrainment of the spray in steam. Under these circumstances, antifoam agents such as polyamides are useful in preventing these entrainment problems. Furthermore, the antifoaming action of polyamides is often enhanced by protective colloid materials such as tannins, and consequently, formulations containing polyamide emulsions in an alkaline tannin base are available. 

CLARIFIER Equipment primarily used to remove suspended solids and/or colloidal materials from a liquid. As applied to sugar, these are normally either flotation (refinery) or sedimentation (factory) devices. See PHOSPHATATION. 

Effluent pretreatment is necessary when RO is used as tertiary treatment in order to prevent membranes filters form being blocked or abraded. UF offers a powerful tool for the reduction of fouling potential of RO/NF membranes [57]. A typical pretreatment consist of a MF allowing the removal of the large suspended solids form the WWTP effluent followed by UF unit which removes thoroughly suspended solids, colloidal material, bacteria, viruses and organic compounds from the filtrated water. The UF product is sent to the RO unit where dissolved salts are removed. 

On the whole, the technology utilized to produce the variety of new nanostructured colloidal materials, as outlined in this chapter, is unparalleled in its versatility and simplicity and is therefore foreseen to become widely used in the engineering of colloidal entities for various applications in the physical and life sciences. 

An important development has been the isolation of bacteria that were able to degrade phenan-threne that was sorbed to humic acid material (Vacca et al 2005). Enrichment was carried ont with PAH-contaminated soils using phenanthrene sorbed to commercial hnmic acid. Only the strains isolated from this enrichment were able to carry ont degradation of C-labeled phenanthrene, and this exceeded by factors of 4-9 the amonnt estimated to be available from the aqneons phase alone. It was snggested that specially adapted bacteria might interact specifically with natnrally occnrring colloidal material. 

At short interparticle distances, the van der Walls forces show that two metallic particles will be mutually attracted. In the absence of repulsive forces opposed to the van der Walls forces the colloidal metal particles will aggregate. Consequently, the use of a protective agent able to induce a repulsive force opposed to the van der Walls forces is necessary to provide stable nanoparticles in solution. The general stabihzation mechanisms of colloidal materials have been described in Derjaguin-Landau-Verway-Overbeck (DLVO) theory. [40,41] Stabilization of colloids is usually discussed... 

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