Filter surface enhancer

Body-aid (i.e., the filter-aid) and precoating are often mentioned in connection with pressure filtration and the difference in their application is (1) Body aid is used when the slurry is low in solids content with fine and slimy particles that are difficult to filter. To enhance filtration coarse solids with large surface area are added to the slurry and serve as a body-aid that captures and traps in its interstices... 

The application of external electrical fields can enhance filtration efficiency beyond a simple system. Bipolar electrostatic charge between the fabric and the particles can induce migration to the filter surface and particle agglomeration in the aerosol. 

Niu Z, Fang Y (2006) Surface-enhanced Raman scattering of single-walled carbon nanotubes on silver-coated and gold-coated filter paper. J Colloid Interface Sci 303 224-228... 

Lasema JJ, Campiglia AD, Winefordner JD (1988) Surface-enhanced Raman spectrometry on a silver-coated filter paper substrate. Anal Chim Acta 208 21-30... 

Let us examine the TFF technique and a typical process regime. Tangential Flow Filtration is the general term used to describe filtration where cross flow parallel to the filter surface is used to enhance filtration rate. This is in contrast to dead ended filtration where the fluid path is solely through the filter. If the membrane used to make the separation is microporous (0.2-0.1+5 urn pore size), the technique is more specifically called mdcroporous tangential flow filtration. Ultrafiltration, a subset of Tangential Flow Filtration, employs a finer, anisotropic membrane able to retain macromolecules, albumin for instance. We will emphasize the use of ultrafiltration membranes in this discussion. 

Filter Ripening In water filtration, the process in which deposition of an initial layer of particles causes the filter surface to take on a nature more similar to the particles to be removed. This process enhances the filtering (hence, removal) of the particles. 

The manifestation of discontinuity in the IR spectra of an ultrathin film can be predicted within the framework of the EMT, treating the film as an effective medium consisting of particles and air. Many EMT studies (see, e.g.. Ref. [346]) have been devoted to metal films because of their applications in solar energy conversion and surface enhancement spectroscopies (see below) and as radiation filters. Some results for ultrathin metallic films will be discussed below. In principle, these should apply to ionic crystal clusters in the spectral range where n < k as well as metallic clusters, because there is no physical difference in the interpretation of absorption spectra of metallic and ionic crystal clusters. 

Recently, the production of nanofibres using nanocomposites has attracted attention. This is due to the fact that this type of nanofibre combines the unique properties of nanocomposites with the outstanding characteristics of nanofibres. Metal/polymer nanocomposites have not only the potential to meet the requirements of applications such as photonic and electric sensors, filters, and artificial tissue, but also can act as catalysts. Silver nanoparticles are the most common embedded metal nanoparticles used in conjunction with polymers. This is because silver nanoparticles exhibit remarkable properties including catalytic activity, surface-enhanced Raman scattering activity, high electrical conductivity and antimicrobial activity. 

KF Wall, RK Chang. Iodine vapor notch filter with optical multichannel detection of low-frequency-shift inelastic scattering from surface-enhanced Raman-scattering active electrodes. Optics Lett 11 493-495, 1986. 

CD Tran. Subnanogram detection of dyes on filter paper by surface-enhanced Raman scattering spectrometry. Anal Chem 56 824-826, 1984. 

The advent of surface-enhanced Raman spectroscopy [435] allows studying extremely low concentrations of molecules on surfaces. Yet SERS is still a rarely applied vibrational technique. Because SERS provides both rich spectroscopic information and high sensitivity as a result of the large enhancement effect, it is an ideal tool for trace analysis as well as for in situ investigations of interfacial phenomena. A number of investigations has explored the possibility of using SERS for direct analysis of species separated by TEC, HPLC and GC. Tran [436] reported sub-ng detection of dyes on filter paper by SERS. 

W. W. Yu, l.M. White, A simple filter-based approach to surface enhanced Raman spectroscopy for trace chemical detection. Analyst 137, 1168 (2012)... 

Mlcrofiltra.tlon, Various membrane filters have been used to remove viral agents from fluids. In some cases, membranes which have pores larger than the viral particle can be used if the filtration is conducted under conditions which allow for the adsorption of the viral particle to the membrane matrix. These are typically single-pass systems having pore sizes of 0.10—0.22 lm. Under situations which allow optimum adsorption, between 10—10 particles of poHovims (28—30 nm) were removed (34—36). The formation of a cake layer enhanced removal (35). The titer reduction when using 0.10—0.22 p.m membrane filters declined under conditions which minimized adsorption. By removal standards, these filters remove vimses at a rate on the low end of the desired titer reduction and the removal efficiency varies with differences in fluid chemistry and surface chemistry of viral agents (26). 

Cake Dewatering. Dewatering (qv), identified as a separate entity in filtration, is used to reduce the moisture content of filter cakes either by mechanical compression or by air displacement under vacuum pressure or drainage in a gravitational or centrifugal system. Dewatering of cakes is enhanced by addition of dewatering aids to the suspensions in the form of surfactants that reduce surface tension. 

Surfactants aid dewatering of filter cakes after the cakes have formed and have very Httle observed effect on the rate of cake formation. Equations describing the effect of a surfactant show that dewatering is enhanced by lowering the capillary pressure of water in the cake rather than by a kinetic effect. The amount of residual water in a filter cake is related to the capillary forces hoi ding the Hquids in the cake. Laplace s equation relates the capillary pressure (P ) to surface tension (cj), contact angle of air and Hquid on the soHd (9) which is a measure of wettabiHty, and capillary radius (r ), or a similar measure appHcable to filter cakes. 

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