Filter coefficient Filtration

Sastry et al. [50] estimated primaquine in its tablet formulation. Powdered tablets equivalent to 100 mg of primaquine phosphate were dissolved in water, filtered, and filtrate was diluted to 100 mL with water. Portions of the solution were shaken with 3 mL of 5 mM brucine-0.16 M sulfuric acid, 1.5 mL of 5 mM sodium periodate and 2 mL of 1.2 M sulfuric acid and diluted to 9 mL with water. The solution was set aside for 20 min in a boiling water bath, cooled, and diluted to 10 mL with water. The absorbance was measured at 510 nm versus a reagent blank. Beer s law was obeyed from 20 to 140 pg/mL of primaquine phosphate. The coefficient of variation was 1.56% (n = 8). Recovery was 99.2%. 

The filter coefficient, X, varies as deposited material changes the morphology of the porous medium and as conditions surrounding the collection sites change. It has been noted that the filtration coefficient increases as fines migrate through a clean filter bed the retained fines increase the specific surface area. This increase in X is short-lived, and the magnitude of the filter coefficient decreases as additional fines are retained. Since Iwasaki published his notes on filtration in 1937, numerous variations of the rate expression have been recorded (72). 

The capture rate equation is similar to the widely accepted rate equation which defines the filter coefficient (X) in deep bed filtration. The rate of removal of particles from a suspension with respect to depth is proportional to the concentration of particles in the suspension (7)... 

Single-collector efficiency for monolayer filtration vreis estimated with the expression developed by Rajagopalan and Tien [128], obtained by the combination of the trajectory analysis of a spherical particle in the vicinity of a spherical collector with the contribution of the Brownian diffusion. For fine-fine capture step, filtration becomes driven by the fine-fine interaction forces yielding a multilayer deposit for which the filter coefficient no longer remains constant in time. The change of the filter coefficient as a function of the specific deposit was estimated using the correlation developed by Tien et al. [129]. Extra information about trickle-bed deep-bed filtration model is given in Iliuta and Larachi [130] and Iliuta et al. [119]. 

The following example helps to illustrate the use of the equations presented up to this point. An aqueous slurry was filtered in a small laboratory filter press with a pressure drop of 0.5 atm and at a temperature of 20 C. After 10 minutes, 4.7 liters of filtrate were obtained after 20 minutes, 7.0 liters were collected. From experiments at other pressures, it was determined that the cake compression coefficient was s = 0.4. We wish to determine the volume of filtrate expected after 30 minutes from a filter press having a filtering area 10 times greater than the laboratory press if the filtration is to be performed at 1.5 atm pressure. The liquid temperature will be 55 °C. We also wish to determine the rate of filtration at the end of the process. 

The flotation unit maximum loading is 2.1 L/s/m2 (3.1 gal/min/ft2). The maximum filtration rate is 1.7 L/s/m2 (2.5 gal/min/ft2). Each filter compartment is backwashed at or more than 10.2 L/s/m2 (15 gal/min/ft2) during the backwash operation. The single-medium backwash filter consists of 28 mm (11 in.) high-grade silica sand. The effective size and uniformity coefficient for the sand are 0.35 mm and 1.55, respectively. 

We will analyze the latter case and follow the argumentation given by Morel and Gschwend (1987). Distinguishing between particles (that are retained in filters or that are separated in centrifugation) and colloids (that are in the filtrate or supernatant) we can characterize an "observed" distribution coefficient. 

Gel Permeation Chromatography. Samples were filtered on columns of Bio-Gel P-6DG (Bio-Rad Laboratories), and columns of Sephadex G-10, G-25, and G-50 (Pharmacia Corp.) using deionized water as eluant. Gel filtration properties are expressed in terms of the distribution coefficient calculated from the relationship = (V - V )/ (V - V ) where the the volume at which a component elutes, is the void volume, and is the total volume of the system. Blue dextran 2,000 and xylose were used to determine and Vj respectively. 

Experimental Technique. The solid material (1-3 g) with known particle size and standard water (30-50 ml) containing the radionuclide of interest were shaken in glass bottles for 8-12 hours at constant temperature (25°C or 65 C). The phases were separated by centrifugation (50 min, 7000 rpm) and the distribution coefficient of the radionuclide was determined from measurements of the remaining activity of the water. Filtration of the samples through 0.2 pm membrane filter did not change the values. 

Dhumal et al. [26] described an individual UV spectrophotometric assay method for the analysis of omeprazole from separate pharmaceutical dosage forms. Powdered tablets, equivalent to 50 mg of the drug, were sonicated with 35 ml of 0.1 M sodium hydroxide for 5 min and diluted to 50 ml with 0.1 M sodium hydroxide. The solution was filtered and a 2-ml portion of the filtrate was diluted to 200 ml with 0.1 M sodium hydroxide before the absorbance of the solution was measured at 305 nm versus 0.1 M sodium hydroxide. Beer s law was obeyed for 6-25 /[Pg.205]

Fluid filters were realized in the low Reynolds number regime [22,23]. It separates the particles and molecules based on the diffusion coefficient while diluting their concentration. The concept of the diffusion-based filtration is shown in Fig. 5. As the two flow streams of sample and dilutant are introduced... 

Shao et al. recommended the use of a simultaneous fluorimetric method for the determination of the dissolution rate of dipyridamole and aspirin tablets [34]. The powdered tablets (equivalent to weight of one tablet) of dipyridamole and aspirin were dissolved in simulated digestive fluids at 37°C, cooled, and diluted to 1 L with simulated digestive juice. The solution was filtered, and a 1 mL portion of the filtrate was mixed with 0.1 M sodium hydroxide and then set aside at room temperature for 1 h. The solution was mixed with 8 mL of phosphoric acid buffer (pH 6.8) and fluorimetrically detected for dipyridamole at 493 nm (excitation at 418 nm). The coefficients of variation for within-day and within 5 days were 2% for both dipyridamole and aspirin. 

The suspended solid content of a 1-liter river water sample is 20 mg/liter. Assume this material is all organic carbon and that Koc, the organic carbon-water partition coefficient for a chemical of interest, is approximately 4000 liter/kg. A laboratory filters the sample before analysis, analyzing the filtrate (water that does pass through the filter) and reporting the chemical concentration, C, of the filtrate. 

A filter so chosen will absorb the Kfi component much more strongly than the Ka component, because of the abrupt change in its absorption coefficient between these two wavelengths. The effect of filtration is shown in Fig. 1-13, in which the partial spectra of the unfiltered and filtered beams from a copper target (Z = 29) are shown superimposed on a plot of the mass absorption coefficient of the nickel filter (Z = 28). 

The proper filter, inserted between sample and counter, can prevent much unwanted radiation from reaching the counter. For example, in the analysis of brasses (Cu-Zn alloys), a Ni filter will pass much of the Cu Koc radiation and absorb most of the Zn Koi. Selective filtration is most effective when the wavelengths to be separated are close together or widely apart, because, in either case, a filter can be chosen with quite different absorption coefficients for the two wavelengths. Balanced filters (Sec. 7-13) have also been used. 

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