Removal mechanism

In addition to lowering the interfacial tension between a soil and water, a surfactant can play an equally important role by partitioning into the oily phase carrying water with it [232]. This reverse solubilization process aids hydrody-namically controlled removal mechanisms. The partitioning of surface-active agents between oil and water has been the subject of fundamental studies by Grieser and co-workers [197, 233]. 

A PVDF membrane filter has been shown to remove >10 particles of vims for vimses >50 nm independent of fluid type (8). Vimses smaller than 50 nm are not removed as efficientiy but are removed in a predictable manner which correlates to the vims particle size. The chemistry of the suspending fluid affects titer reduction for vimses <50 nm owing to other removal mechanisms, such as adsorption, coming into play. The effects of these other mechanisms can be minimized by using filtration conditions that minimize adsorption. 

The differences in the amino acid chemistry of the hide coUagen and the hair keratin are the basis of the lime-sulfide unhairing system. Hair contains the amino acid cystine. This sulfur-containing amino acid cross-links the polypeptide chains of mature hair proteins. In modem production of bovine leathers the quantity of sulfide, as Na2S or NaSH, is normally 2—4% based on the weight of the hides. The lime is essentially an unhmited supply of alkah buffered to pH 12—12.5. The sulfide breaks the polypeptide S—S cross-links by reduction. Unhairing without sulfide may take several days or weeks. The keratin can be easily hydrolyzed once there is a breakdown in the hair fiber stmcture and the hair can be removed mechanically. The coUagen hydrolysis is not affected by the presence of the sulfides (1—4,7). 

Many older finishes can be removed with single solvents or blends of petroleum solvents and oxygenates. Varnish can be removed with mineral spirits, shellac can be stripped with alcohols, and lacquers can be removed with blends of acetates and alcohols (lacquer thinners). The removal mechanism is one of dissolving the coating, then washing the surface or wiping away the finish. This method is often used to reamalgamate or liquefy old finishes on antique items of furniture. 

Acids and alkaUes were used to decompose the fiber to cellulose. The alkaU digester process, developed in 1899, is stiU used. Fiber glass reinforcement must be removed mechanically before the mbber can be reclaimed. A highly efficient method involves hammer mills and reel beaters to separate the fiber from the mbber an air current subsequentiy drives off the fiber. 

Alternatively, induced air flotation (lAF) can be employed, in which air bubbles are generated through an inductor. The removal mechanism is the same as the DAF. 

The efficiency of the vegetable matter (burr and seeds) removal mechanism depends on the carefiil maintenance of settings and speeds and the level of drying of the scouted wool (86). The butt wastes contain wool fiber. Butt, together with fiber which has dropped beneath the card, may be carbonized and used in the woolen system. 

The water removal mechanism is adsorption, which is the mechanism for ad Class 4 drying agents. The capacity of such materials is often shown in the form of adsorption isotherms as depicted in Figures 9a and 9b. The initial adsorption mechanism at low concentrations of water is beheved to occur by monolayer coverage of water on the adsorption sites. As more water is adsorbed, successive layers are added until condensation or capidary action takes place at water saturation levels greater than about 70% relative humidity. At saturation, ad the pores are fided and the total amount of water adsorbed, expressed as a Hquid, represents the pore volume of the adsorbent. 

Sedimentation. This is the traditional method of treating wastewater in lagoons and uses the force of gravity to remove settable soHds (50,51). These soHds are separated out as a watery sludge which is removed mechanically. 

Product removal mechanisms from apparatuses that are explosion resistant can be protected with a. double-slide system. Here, the shdes must be at least as resistant as the apparatuses. By means of proper control, it must be assured that a shde is always closed. 

Dry aerosols, or particulate matter, differ so much from the carrying gas stream that their removal should present no major difficulties. The aerosol is different physically, chemically, and electrically. It has vastly different inertial properties than the carrying gas stream and can be subjected to an electric charge. It may be soluble in a specific liquid. With such a variety of removal mechanisms that can be applied, it is not surprising that particulate matter, such as mineral dust, can be removed by a filter, wet scrubber, or electrostatic precipitator with equally satisfactory results. 

Since mist and droplets differ significantly from the carrying gas stream, just as dry parhculates do, the removal mechanisms are similar to those employed for the removal of dry particulates. Control devices developed particularly for condensing mists will be discussed separately. Mist collcc-hon is further simplified because the parhcles are spherical and tend to resist reentrainment, and they agglomerate after coming in contact with the surface of the collechng device. 

V. Removal Mechanisms References Suggested Reading Questions... 

With the cxoepLion, howev V, o( trierhyl citrate, nearly all the nonvolatile esters are to a great extent, removed mechanically during the evaporation in tbe oil vapour- To delect, Cor example, glycer) acetate, ethyl oxalate., ethyl tarlrate, aod ethyl succinate, the evaporation should only be proceeded with until about 10 to 16 pet cent, of the oil is left in the dtsb, and this residee tested for Ibe varioua acids,... 

A simple pendulum isolated from nonconseiwative forces would oscillate forever. Complete isolation can never be achieved, and the pendulum will eventually stop because nonconsewative forces such as air resistance and surface friction always remove mechanical energy from a system. Unless there is a mechanism for putting the energy back, the mechan-... 

It has been seen that iron has an adverse effect because it forms a second phase (insoluble) material in the alloy which acts as an effective local cathode. Sequestering is the technique of adding an alloying addition that will cause an alternative intermetallic compound with iron to form. This compound might form a dross to be removed mechanically. Alternatively the new intermetallic compound could be a less effective cathode in which case removal would not be necessary. 

Used anodically it readily forms a protective film which is reformed if removed mechanically. This is grey-white in appearance and has a tendency to flake under the compressive stress produced at thickened areas. The film... 

Li, Y.-H. (1981). Ultimate removal mechanisms of elements from the ocean. Geochim. Cosmochim. Acta 45,1659-1664. 

Kudo, A. (1983). Physical/chemical/biological removal mechanisms of mercury in a receiving stream. In Toxic Materials - Methods for Control" (N. E. Armstrong and A. Kudo, eds). The Center for Research in Water Resources, University of Texas at Austin, Austin, TX. 

Metal polishing mechanisms appear to be considerably different from silica polishing. The critical event that determines the polishing process in metal CMP appears not only to be influenced by the crystallographic/microstructure deformation process but also to relate to more complex components of slurry [18]. To better understand the removal mechanism in metal CMP, tungsten is chosen, since both industrial and laboratory CMP data are available for this metal, and its abrasion behavior as a metal is similar to that of other ductile metals which have been studied quite extensively under two- and three-body abrasion [66]. 

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