Bleach filtration

BFR [Bleach filtrate recycle] A process for almost completely recycling the waste liquors from pulp-bleaching using chlorine dioxide. The key to the process is the separation of the sodium sulfate from potassium chloride by crystallization. Developed by Champion International Corporation, Sterling Pulp Chemicals, and Wheelabrator Technologies. It was proposed for installation in North Carolina in 1997. 

Rendered fats have many other industrial uses. In these other uses, more than 70% require such processes as refining, bleaching, filtration, hydrogenation, traMi-esterification, and winterization before they can be converted to more useful products. All of these products and processes fall under the general category of oleochemistry. 

Bleach Filtration. The discussion of brine treatment in Section 7.5 covered the characteristics of the particles formed by chemical precipitation and the types of filter used to remove them. As that discussion would indicate, the particles found in bleach solutions are not easy to filter. Filter aids are necessary, and pressure-leaf filters are commonly used. Figure 15.17 shows a typical skid-mounted unit. Pumps and bleach filter bodies and plates should be titanium. Nonmetallic components are PVC or PTFE. Other components of the system (e.g., filter aid tanks) may be FRP. Filter aids should be diatomaceous earth or Perlite (Section 7.5.4.2). 

Raw lac is first treated to remove water-soluble carbohydrates and the dye that gives lac its red color. Also removed are woody materials, insect bodies, and trash. It is further refined by either hot filtration or a solvent process. In the heat process, the dried, refined lac is filtered molten through cloth or wine screens to produce the standard grades of orange shellac. In the solvent process, lac is dissolved and refluxed in alcohol solvents, filtered to remove dirt and impurities, and concentrated by evaporation. The lac can be further decolori2ed in this process to produce very pale grades. Bleached shellac is prepared by treatment with dilute sodium hypochlorite and coalesced into slabs. 

Diacetone-L-sorbose (DAS) is oxidized at elevated temperatures in dilute sodium hydroxide in the presence of a catalyst (nickel chloride for bleach or palladium on carbon for air) or by electrolytic methods. After completion of the reaction, the mixture is worked up by acidification to 2,3 4,6-bis-0-isoptopyhdene-2-oxo-L-gulonic acid (2,3 4,6-diacetone-2-keto-L-gulonic acid) (DAG), which is isolated through filtration, washing, and drying. With sodium hypochlorite/nickel chloride, the reported DAG yields ate >90% (65). The oxidation with air has been reported, and a practical process was developed with palladium—carbon or platinum—carbon as catalyst (66,67). The electrolytic oxidation with nickel salts as the catalyst has also... 

Filter aids may be applied in one of two ways. The first method involves the use of a precoat filter aid, which can be applied as a thin layer over the filter before the suspension is pumped to the apparatus. A precoat prevents fine suspension particles from becoming so entangled in the filter medium that its resistance becomes exces-sive. In addition it facilitates the removal of filter cake at the end of the filtration cycle. The second application method involves incorporation of a certain amount of the material with the suspension before introducing it to the filter. The addition of filter aids increases the porosity of the sludge, decreases its compressibility, and reduces the resistance of the cake. In some cases the filter aid displays an adsorption action, which results in particle separation of sizes down to 0.1 /i. The adsorption ability of certain filter aids, such as bleached earth and activated charcoals, is manifest by a decoloring of the suspension s liquid phase. This practice is widely used for treating fats and oils. The properties of these additives are determined by the characteristics... 

To a solution of m-ethyl cinnamate (44, 352 mg, 85% pure, 1.70 mmol) and 4-phenylpyridine-A-oxide (85.5 mg, 29 mol%) in 1,2-dichloromethane (4.0 mL) was added catalyst 12 (38.0 mg, 3.5 mol%). The resulting brown solution was cooled to 4°C and then combined with 4.0 mL (8.9 mmol) of pre-cooled bleach solution. The two-phase mixture was stirred for 12 h at 4°C. The reaction mixture was diluted with methyl-t-butyl ether (40 mL) and the organic phase separated, washed with water (2 x 40 mL), brine (40 mL), and then dried over Na2S04. The drying agent was removed by filtration the mother liquors concentrated under reduce pressure. The resulting residue was purified by flash chromatography (silica gel, pet ether/ether = 87 13 v/v) to afford a fraction enriched in cis-epoxide (45, cis/trans . 96 4, 215 mg) and a fraction enriched in trans-epoxide cis/trans 13 87, 54 mg). The combined yield of pure epoxides was 83%. ee of the cis-epoxide was determined to be 92% and the trans-epoxide to be 65%. 

The oxygen either bubbles out of the solution or attacks oxidizable material. Calcium hypochlorite is the main component of bleach powders and is used for purifying the water in home swimming pools. It is used for swimming pools in preference to sodium hypochlorite because the Ca2+ ions form insoluble calcium carbonate, which is removed by filtration sodium would remain in solution and make the water too salty. 

Bleach plant washer filtrates Paper machine-water flows Fiber and liquor spills... 

Opportunities for reducing effluent flows and water use are also present in the bleaching plant. Acid filtrates from hypochlorite or chlorine dioxide stages can be used as dilution and wash water for the first bleaching stage. Similarly, second extraction stage filtrates can be used as dilution and... 

Purify the labeled protein from excess dye using dialysis or gel filtration on a desalting resin. Protect the labeled protein from light to avoid photo bleaching the dye and losing fluorescence intensity. 

Figure 4. The transport of by Chlorella under Os stress A. Control efflux from pre-loaded cells. A culture of 38°C-grown C. sorokiniana was preloaded with for 24 hrs. Cells were concentrated by centrifugation, washed, and resuspended as described in Figure 1, and assayed for Rfo loss by millipore filtration. The cells were dried, bleached, and counted by liquid scintillation as described by Fredrick and Heath (24). B. Influx into cells. A culture of exponentially growing C. sorokiniana was centrifuged, washed, resuspended in the Tris-Cl solution (see Figure 1) plus 100 fjM KCl, and placed in a 38°C water bath. At time intervals after RB addition, samples of cells were assayed as described in A.

With higher bleach concentrations proportionally less is added, and twice the recommended amount should be used if the water remains cloudy after filtration. 

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