Hypochlorites filtration

In another process, hypochlorite filtrate is treated with lime slurry to precipitate dibasic crystals that are filtered. The filtrate is mixed with strong caustic, chlorinated, and filtered to remove NaCl crystals. The filtrate containing Na and Ca hypochlorite is mixed with dibasic crystals and chlorinated producing a slurry of Ca(OCl)2 is filtered the cake goes to a dryer and the filtrate to the dibasic crystallizer (195). 

A solution of 2-aminobenzophenone (98 g, 0.50 mol) and methyl 2-(methyl-thio)propanoate (74 g, 0,50 mol) in CH Clj (21) was cooled to —70 C and 95% 7-butyl hypochlorite (56 g, 0.5 mol) was added dropwise at such a rate that the temperature did not rise above — 65 C. One hour after the addition was complete, EtjN was added and the mixture was allowed to come to room temperature. The solution w as mixed with 3 N HCl (800 ml) and stirred for 1 h. The organic layer was separated, dried (Na2S04 ) and filtered. The solution was evaporated in vacuo and the residue triturated with ether. Filtration gave the 3-(methylthio)oxindole intermediate (92 g) in 62% yield. 

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... 

Other processes also use the dibasic salt as an intermediate. Dibasic calcium hypochlorite can be prepared from filtrates from chlorinated lime slurries in various ways. In one process, the filtrate is returned to the slurry being chlorinated to keep it thin. This is designed to improve crystal growth. The dibasic crystals, together with water, are added to the slurry during chlorination and some dibasic salt is prepared by chlorination in addition to the dibasic salt made from filtrates (188). In another process, dibasic crystals are separated, slurried in water, and chlorinated to obtain a slurry of neutral Ca(OCl)2 2H20 in a mother Hquor of reduced calcium chloride content which is then filtered and air dried (191,192). 

Two cocrystallization processes employ dibasic crystals as intermediates. The PPG process (199—202) is discussed under commercial processes. The PPC process (203) forms dibasic crystals from lime and recovered filtrates. The dibasic crystals are separated from thek mother liquor by decantation, slurried in caustic solution and chlorinated to produce a cocrystalline slurry of Ca(OCl)2 and NaCl. The slurry is sent to a flotation cell where the larger salt crystals settle out and the smaller hypochlorite crystals float to the top with the aid of ak and flotation agent. The hypochlorite slurry is centrifuged the cake going to a dryer and the centrate to the flotation cell. The salt-rich bottoms from the flotation cell are centrifuged and washed with dibasic mother Hquor. The centrates are recycled to the precipitation step. 

In another cocrystalHzation process, lime is mixed with 50% caustic and recycled filtrate and chlorinated to yield a slurry of calcium hypochlorite dihydrate and NaCl crystals that are separated in a hydrauHc classifier. The underflow is mixed with centrate mother Hquor and sent to a wet screen classifier the overflow is recycled to the hydroclone and the salt-rich bottoms are centrifuged. The centrate is recycled to the chlorinator and the salt used as feed to chloralkaH ceUs. The Ca(OCl)2-rich overheads from the hydroclone are centrifuged, the cake going to a dryer and the filtrate sent to the wet screen classifier (207). 

Commercial Processes. Olin s earlier triple salt process, originally commercialized in 1928, was modified in 1983. In the patented process, a slurry of dibasic calcium hypochlorite is mixed with a strong, low salt sodium hypochlorite solution and hypochlorite Hquors and chlorinated. The resultant Ca(OCl)2 2H20 slurry is filtered, the cake going to the dry-end and the filtrate to the dibasic precipitation step where it reacts with lime. 

Manufacture. Hemibasic calcium hypochlorite is manufactured by chlorination of lime slurry followed by filtration and dryiag of the filter cake. 

In a 3-I. round-bottomed flask 250 g. of commercial calcium hypochlorite is dissolved in i 1. of warm water and a warm solution of 175 g. of potassium carbonate and 50 g. of potassium hydroxide in 500 cc. of water is added. The flask is stoppered and shaken vigorously until the semi-solid gel which first forms become quite fluid. The suspended solid is removed by filtration on a large Buchner funnel, washed with 200 cc. of water, and sucked as dry as possible with the aid of a rubber dam and an efficient suction pump. The filtrate of approximately 1500 cc. is placed in a 3-I. round-bottomed flask and is ready for the addition of methyl /3-naphthyl ketone. 

A 3-1., three-necked flask fitted with a mechanical stirrer, a dropping funnel, and a thermometer is then charged with an aqueous solution of 2.2 moles of calcium hypochlorite [Hypochlorous acid, calcium salt] (Note 3), and the piperidine acetate prepared above is placed in the dropping funnel. The hypochlorite solution is stirred and cooled to 0° to — 5° with a methanol-ice bath, and the piperidine acetate is added dropwise over a period of 1.25 hours while the temperature is maintained below 0°. After a further 15 minutes of stirring, equal portions of the mixture are placed in two 2-1. separatory funnels and extracted three times with a total of about 1300 ml. of ether. The ether extract is placed in a 2-1. flask and dried over anhydrous sodium sulfate in a cold room at 4° overnight. After filtration to remove inorganic material, the bulk of the ether is removed by boiling on a water bath maintained below 60° (Note 4). 

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. 

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... 

B. Benzofurazan oxide. A mixture of 21 g. (0.32 mole) of potassium hydroxide and 250 ml. of 95% ethanol in a 1-1. Erlenmeyer flask is heated on a steam bath until the solid dissolves (Note 1). o-Nitro-aniline (40 g., 0.29 mole) (Note 2) is dissolved in the warm alkali solution. The resulting deep red solution is then cooled to 0°, and the sodium hypochlorite solution from part A is added slowly with good stirring over the course of 10 minutes (Note 3). The flocculent yellow precipitate is collected on a large Buchner funnel, washed with 200 ml. of water, and air-dried. The crude product weighs 36.0-36.5 g. and melts at 66-71° (Note 4). The product is purified by recrystallization from a solution made up from 45 ml. of 95% ethanol and 15 ml. of water. Material insoluble in the hot solvent is removed by filtration, and the hot filtrate is allowed to cool to room temperature. The yield of yellow benzofurazan oxide is 31.6-32.5 g. (80-82%), m.p. 72-73°. 

Thann A process for making crystalline calcium hypochlorite by passing chlorine into an aqueous slurry of calcium hydroxide. There are several such processes in this one, some of the filtrate is recycled in order to produce larger crystals. Invented by J. Ourisson in France in 1936. 

Other Important Considerations with Membranes Oxidizers such as sodium hypochlorite (i.e., CIO2), bromine, iodine, and ozone, which are typically used in the disinfection of wastewater, are not well tolerated by thin-hlm membranes. Such disinfectants can thus influence the efficacy of membranes in removing contaminants such as PPCPs. Furthermore, membranes can become fouled by microorganisms that can metabolize the membrane material. Thus, microbial counts of >100 cells/mL can be problematic. Likewise, dead-cell debris can also cause fouling. Membranes can also be fouled by heavy metals such as chromium. Thus, if heavy metals are deemed a problem, they should be precipitated from the wastewater prior to the filtration with membranes. 

To 10.0 gm (0.0546 mole) of pentafluoroaniline is added 360 ml of a sodium hypochlorite solution containing 10-14% w/v available chlorine. The mixture is stirred vigorously at room temperature for 4 hr. Then the crude product is isolated by repeated extraction with ether. The ether extract is washed with deionized water until the water contains no significant levels of chloride ions. The ether solution is dried with sodium sulfate, filtered, and the filtrate is evaporated cautiously to dryness. The residue is recrystallized from ethanol yield 2.5 gm (25.3%), m.p. 142°-143°C. 

Methyl 3-methoxy-596 7,8-tetrahydro-2-naphthoate—To 300 ml of potassium hypochlorite solution [12] (ca. 0 46 mole of hypochlorite) at 11° was added, with stirring, 2 0 g (0 0098 mole) of 3-methoxy-5,6,7,8-tetrahydro- 2 acetonaphthone in 60 ml of methanol. The mixture was stirred for 5 hours at 11-30°. Filtration separated 0 92 g of yellow... 

A practical consideration in working with ethanethiol is the pervasive stench of this and other volatile thiols, especially as such thiols are used in minute concentration as odor markers for natural gas. It is not easy to perform the standard preparative procedures, during which transfer and filtration operations are performed, in a closed system, and vapors carried through a venting system are detectable at considerable distances, hr small-scale operations, it may be possible to employ a sodium hypochlorite trap to convert the thiols into nonvolatile, oxidized products. 

Chlorination is the most widely used disinfecting or sterilizing process. Where daily water requirements arc not large, it is common practice to use a hypochlorite, but for large plants liquefied chlorine gas is used. Chlorination may be practiced before filtration (prechlorination), after filtration (post-chlorination), or both before and after. 

Chlorine is passed into 250 c.cs. water containing 45 gms. caustic soda until the total weight is 332 gms. 750 c.cs. of ice-water are then added. A solution prepared from commercial sodium hypochlorite (p. 512) may be employed. Into the cold solution are slowly run 27 gms. p-pheny-lenediamine hydrochloride in 300 c.cs. of water and 60 c.cs. of cone, hydrochloric acid. After the blue colour disappears the dichlorimide separates, is filtered and washed with water until the filtrate is free from chlorine it is then recrystallised from 70% alcohol or petroleum ether (40°—60°). 

Sodium Hypochlorite (NaOCl).—1. Excess of sodium carbonate is added to a solution of bleaching powder. The filtrate, after removing the CaC03, contains the available chlorine, and the solution can be kept for some time. 

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