Methods filtration

The coal-derived pitch precursors for WVU-1, WVU-2, and WVU-3 test graphites were de-ashed by the combined centrifugation and filtration method while all of the other pitches were de-ashed by centrifugation alone (2000 G, 90 minutes). 

Nitrophosphate fertilizer is made by digesting phosphate rock with nitric acid. This is the nitrophosphate route leading to NPK fertilizers as in the mixed-acid route, potassium and other salts are added during the process. The resulting solution is cooled to precipitate calcium nitrate, which is removed by filtration methods. The filtrate is neutralized with ammonia, and the solution is evaporated to reduce the water content. The process of prilling may follow. The calcium nitrate filter cake can be further treated to produce a calcium nitrate fertilizer, pure calcium nitrate, or ammonium nitrate and calcium carbonate. 

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. 

In certain plants, especially in the chemical industry or in the neighborhood of such plants, the air is often polluted with acidic and corrosive gases that can cause corrosion in the compressor and the compressed air system. Special filtration methods and/or materials may have to be used and the supplier should be consulted. 

In general, fungal mycelia are filtered relatively easily, because mycelia filter cake has sufficiently large porosity. Yeast and bacteiia are much more difficult to handle because of thefr small size. Alternative filtration methods, which eliminate the filter cake, are becoming more acceptable for bacterial and yeast separation. Micro-filtration is achieved by developing large cross-flow fluid velocities across the filter surface while the velocity vector normal to the surface is relatively small. Build up of filter cake and problems of high cake resistance are therefore prevented. Micro-filtration is not discussed in this section. 

Other Pyrochemical Processes. The chemistry of pyrochemi-cal separation processes is another fertile area of research e.g., new molten salt systems, scrub alloys, etc. and the behavior of plutonium in these systems. Studies of liquid plutonium metal processes should also be explored, such as filtration methods to remove impurities. Since Rocky Flats uses plutonium in the metal form, methods to convert plutonium compounds to metal and purify the metal directly are high-priority research projects. 

Displacement binding experiments with 3H-PCP were conducted with minor modifications of the filtration method described in the literature (Zukin and Zukin 1979 Vincent et al. 1979 Hampton et al. 1982) in crude tissue preparations of rat whole brain homogenates in 5 mM Tris-HCl (pH 7.4). 

The purpose of a sterility test is to determine the probable sterility of a specific batch. The USP lists the procedural details for sterility testing and the sample sizes required [1], The USP official tests are the direct (or culture tube inoculation) method and the membrane filtration method. 

W6. Wang, Y. S., Pekary, A. E England, M. L., and Hershman, J. M., Comparison of a new ultra-filtration method for serum free T4 and free T, with two RIA kits in eight groups of patients. J. Endocrinol. Invest. 8,495-500 (1985). 

Filtration is also used to purify CNTs. Bandow [29] have reported a procedure for a one-step SWNT purification by microfiltration in an aqueous solution with a cationic surfactant. Shelimov [30] developed an ultrasonically assisted filtration method which allows the purity of nanotubes to reach >90%. 

A prerequisite for the application of filtration methods is a significant difference in molecular size of the catalyst and the reactants / products. Molecular enlargement, i.e. binding the homogeneous catalyst to soluble supports, is often the method of choice. These supports can be dendrimers, hyper-branched polymers or even simple polymers, giving the opportunity to tailor the support according to the given process. 

The cross-flow filtration method is applied mainly to hyper- and ultrafiltration as well as to some microfiltration.8 In cross-flow filtration the slurry solution or suspension fed to the filter flows parallel to the filter medium or membrane. The filtration product (permeate or filtrate) leaves the filtration module at right angles to the filter medium (the membrane). The traditional perpendicular flow filtration (where the flow of the suspension is directed at right angles to the filter medium and the permeate leaves the filter medium in the same direction) entails filter cake buildup, whereas cross-flow filtration is intended to prevent such filter... 

FIGURE 6.31 Comparison of solubility results obtained by no-filtration method followed by PLC detection and those obtained by two traditional methods multiscreen filtration followed by UV plate reader, and shake flask method followed by UV plate reader. (Data provided by Steven Hobbs, Courtney Coyne, and Gregory Kazan.)... 

Maayani, S., and Weinstein, H. (1980) Specific binding of 3H-phencyclidine Artifacts of the rapid filtration method. Life Sci., 26 2011-2022. 

Soil solution samples from saturated soils can be obtained by simple filtration. Simple gravity filtration is preferable to vacuum filtration methods because vacuum filtration can lead to distortions in the composition of analyte composition in filtrates. Syringe filters are usually not capable of handling soil and so are not recommended. Also, some filters can retain analytes of interest. 

Vacuum filtration involves carrying out filtration under reduced pressure and provides a faster method of separating a precipitate from a filtrate than traditional gravity filtration methods. A Buchner, Hirsch or sintered glass funnel can be used during vacuum filtration. 

C. W. Microplate gel-filtration method for radiohgand-binding assays. Anal. Biochem. 2002, 308, 127-133. 

Biological fouling was monitored using the customary indicators of RO performance, including flux (productivity), salt passage, and bundle pressure drops (AP). In addition, the total bacteria count (TBC) of the RO feed water and the reject brine stream were also obtained using the membrane filtration method (Ref. 6). The increase in TBC between the feed and reject portions of the system had been found in the preliminary stages of... 

T) BGT binding to the receptor is assayed using a filtration method (40). 

Cooper, P.F. and Wood, G.C. (1968) Protein binding of small molecules new gel filtration method. Journal of Pharmacy and Pharmacology, 20, 150S-156. 

Whole-body isotope retention experiments were performed (via the method described above in the Smith experiment and with confirmed corrections for isotope decay rates), using extrinsically labeled ferric chloride hexahydrate and Ca from CCM (i.e., [ FeJFeCla and [" Ca] CaCl2) to determine the bioavailability of these minerals at an Fe Ca ratio of 1 167 mol/mol. CCM solubility was also assessed via a filtration method. 

Since membrane filtration methods such as ultra filtration or nanofiltration can discriminate according to the size of a given molecule, they can easily be used to retain biocatalysts (which are macromolecules). For chemical catalysts additional procedures have to be applied mostly. Immobilization on a solid support is used... 

Total aerobic viable count per standard test method (provide reference number) using membrane filtration method. Sample 100 ml shall be filtrated and placed on low-nutrient content media, at 20 to 22°C for 5 days and observed for another 2 days. 

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