Stripping concentrated

During the staining of strips, concentration of buffer salts increases progressively in the bath, as the strips are not previously washed but are merely dried in the oven. The presence of salts depresses the dye-binding capacity of protein (F5). The use of a fixing bath before the staining may remove up to 80 % of the salts, and also assure a uniform denatura-tion of the proteins (F6, S20, W13). 

Another method for recovering strontium from NaCI stripping concentrates as well as from natural underground brines of similar composition has been examined in the laboratory of Professor V. I. Gorshkov at Moscow State University [254-256]. 

Effect of Feed to Strip Ratio. Further experiments were performed to Investigate the effect of feed-to-strlp (F S) ratio on americium transfer and to evaluate the possibility of concentrating the metal Ions simultaneously with removal. A linear relationship would be expected between the F S ratio and the concentration factor, the ratio of the final strip concentration divided by the Initial feed concentration assuming no complications arise. However, the results shown In Table IV Indicate the actual concentration factor Is much less than the F S ratio, possibly because a large fraction of the americium Is held In the membrane at the conclusion of the run. In addition, the relationship between the ratio and the percent transferred Is roughly Inverse because of the Increased amount of nitric acid transferred Into the strip solution with larger feed volumes. 

The flux can be also calculated referring to strip concentration, thus considering only the... 

The liquid ammonia absorbs salt, chlorate, carbonate, water, and some cau.stic. It is then stripped, concentrated, and returned to the extraction process. The concentrated caustic leaving the extractor is stripped free of ammonia, which is recovered, concentrated, and recirculated. Typical purities before and after caustic purification are shown in Table 20. This process is offered for license by PPG Industries and OxyTech Systems. 

Figure 11 Sulfuric acid strip concentrations on tandem columns 1-3 after each load cycle with iron-precipitated Berkeley Pit water at pH 4.1.

Figure 28.8 Strontium concentrations in feed and strip solutions as a function of time in recycle operation for four extractants (C12 feed concentration in the feed solution for the C12 BOPPA extractant C12 strip concentration in the strip solution for the C12 BOPPA extractant in the same way for the C16 HDPPA, C18 ODPPA/HDPPA, and C20 ODPPA extractants the aqueous feed solutions also contained about 80 ppm calcium, 20 ppm magnesium, and 50 ppm zinc in addition to Sr-87) (Ho and Wang, 2002).

This SLM also removed Sr-90 to a concentration of 352 pCi/L or lower from feed solutions containing 30,000 pCi/L Sr-90 (also shown in Table 28.1) with and without the presence of about 80 ppm calcium, 20 ppm magnesium, and 50 ppm zinc. The strip concentration was concentrated to more than 263,000 pCi/L (with an aqueous strip solution volume of about 220 mL, that is, a feed-to-strip solution volume ratio of about 9). Based on the results for the feed solutions of 317-1000 pCi/L, the treated concentration of 352pCi/L or lower (in the treated solutions), which is lower than lOOOpCi/L, can be reduced to meet the target concentration of 8 pCi/L or lower by the use of a second SLM step. 

Agar occurs as a cell-wall constituent of the red marine algae Rho ophyceae, from which it is extracted by hot water, and marketed as a dry powder, flakes, or strips. It dissolves in hot water and sets on cooling to a jelly at a concentration as low as 0-5%. Its chief uses are as a solid medium for cultivating micro-organisms, as a thickener, emulsion stabilizer in the food industry and as a laxative. 

Stripping voltammetry involves the pre-concentration of the analyte species at the electrode surface prior to the voltannnetric scan. The pre-concentration step is carried out under fixed potential control for a predetennined time, where the species of interest is accumulated at the surface of the working electrode at a rate dependent on the applied potential. The detemiination step leads to a current peak, the height and area of which is proportional to the concentration of the accumulated species and hence to the concentration in the bulk solution. The stripping step can involve a variety of potential wavefomis, from linear-potential scan to differential pulse or square-wave scan. Different types of stripping voltaimnetries exist, all of which coimnonly use mercury electrodes (dropping mercury electrodes (DMEs) or mercury film electrodes) [7, 17]. 

Anodic-stripping voltaimnetry (ASV) is used for the analysis of cations in solution, particularly to detemiine trace heavy metals. It involves pre-concentrating the metals at the electrode surface by reducmg the dissolved metal species in the sample to the zero oxidation state, where they tend to fomi amalgams with Hg. Subsequently, the potential is swept anodically resulting in the dissolution of tire metal species back into solution at their respective fomial potential values. The detemiination step often utilizes a square-wave scan (SWASV), since it increases the rapidity of tlie analysis, avoiding interference from oxygen in solution, and improves the sensitivity. This teclmique has been shown to enable the simultaneous detemiination of four to six trace metals at concentrations down to fractional parts per billion and has found widespread use in seawater analysis. 

Adsorptive stripping analysis involves pre-concentration of the analyte, or a derivative of it, by adsorption onto the working electrode, followed by voltanmietric iiieasurement of the surface species. Many species with surface-active properties are measurable at Hg electrodes down to nanoniolar levels and below, with detection limits comparable to those for trace metal detemiination with ASV. 

The current during the stripping step is monitored as a function of potential, giving rise to peak-shaped voltammograms similar to that shown in Figure 11.37. The peak current is proportional to the analyte s concentration in the solution. 

When either pulse polarography or anodic stripping voltammetry can be used, the selection is often based on the analyte s expected concentration and the desired... 

The concentration of copper in a sample of sea water is determined by anodic stripping voltammetry using the method of standard additions. When a 50.0-mL sample is analyzed, the peak current is 0.886 )J,A. A 5.00-)J,L spike of 10.0-ppm Cu + is added, giving a peak current of 2.52 )J,A. Calculate the parts per million of copper in the sample of sea water. 

Peak currents in anodic stripping voltammetry are a linear function of concentration... 

The speciation scheme of Batley and Florence requires eight measurements on four samples. After removing insoluble particulates by filtration, the solution is analyzed for the concentration of anodic stripping voltammetry (ASV) labile metal and the total concentration of metal. A portion of the filtered solution is passed through an ion-exchange column, and the concentrations of ASV metal and total metal are determined. A second portion of the filtered solution is irradiated with UV light, and the concentrations of ASV metal... 

A typical flow diagram for pentaerythritol production is shown in Figure 2. The main concern in mixing is to avoid loss of temperature control in this exothermic reaction, which can lead to excessive by-product formation and/or reduced yields of pentaerythritol (55,58,59). The reaction time depends on the reaction temperature and may vary from about 0.5 to 4 h at final temperatures of about 65 and 35°C, respectively. The reactor product, neutralized with acetic or formic acid, is then stripped of excess formaldehyde and water to produce a highly concentrated solution of pentaerythritol reaction products. This is then cooled under carefully controlled crystallization conditions so that the crystals can be readily separated from the Hquors by subsequent filtration. 

Caustic Soda. Diaphragm cell caustic is commercially purified by the DH process or the ammonia extraction method offered by PPG and OxyTech (see Fig. 38), essentially involving Hquid—Hquid extraction to reduce the salt and sodium chlorate content (86). Thus 50% caustic comes in contact with ammonia in a countercurrent fashion at 60°C and up to 2500 kPa (25 atm) pressure, the Hquid NH absorbing salt, chlorate, carbonate, water, and some caustic. The overflow from the reactor is stripped of NH, which is then concentrated and returned to the extraction process. The product, about 62% NaOH and devoid of impurities, is stripped free of NH, which is concentrated and recirculated. MetaUic impurities can be reduced to low concentrations by electrolysis employing porous cathodes. The caustic is then freed of Fe, Ni, Pb, and Cu ions, which are deposited on the cathode. 

There are two methods available for aroma recovery. In one method, a portion of the water is stripped from the juice prior to concentration and fractionally distilled to recover a concentrated aqueous essence solution. Apple juice requires 10% water removal, peach 40%, and Concord grape 25—30% to remove volatile flavor as an essence. Fractional distillation affords an aqueous essence flavor solution of 100—200-fold strength, which means the essence is 100 to 200 times more concentrated in flavor than the starting juice. A second method of essence recovery is to condensate the volatiles from the last effect of the evaporator they are enriched in volatile flavor components (18). 

Inversion ofMon cjueous Polymers. Many polymers such as polyurethanes, polyesters, polypropylene, epoxy resins (qv), and siHcones that cannot be made via emulsion polymerization are converted into latices. Such polymers are dissolved in solvent and inverted via emulsification, foUowed by solvent stripping (80). SoHd polymers are milled with long-chain fatty acids and diluted in weak alkaH solutions until dispersion occurs (81). Such latices usually have lower polymer concentrations after the solvent has been removed. For commercial uses the latex soHds are increased by techniques such as creaming. 

---