Activated carbon concentration

Stirring is continued for 2 hours at room temperature, and then methanol is added until a clear solution is obtained (ca. 10 ml. of methanol is required, and some heat is generated). When the solution has cooled, it is washed successively with 200 ml. of aqueous 2N potassium carbonate and 200 ml. of water. The aqueous phases are combined, washed with three 100-ml. portions of chloroform, and discarded. The organic phases are then combined, dried over sodium sulfate, and decolorized with activated carbon. Concentration of the chloroform solution thus obtained provides three crops of pale yellow crystals, which are washed with 30% hexane in chloroform and dried for 2 hours at 80°/0.1 mm. The total yield of 3-(2-phenyl-l,3-dithian-2-yl)indole is 22.3-25.4 g. (72-81%), m.p. 167-169° (Note 7). This material requires no further purification for use in Parts D or E. 

Downstream processing may consist of several operations such as liming to precipitate the metabolite as the calcium salt, washing of the precipitate with water to remove soluble impurities, acidification using strong acids to convert the salt in its free acid form. The acidic liquor may be demineralized using IER, decolorized using active carbons, concentrated under vacuum, and finally crystallized. 

C. Preparation of 2-oxo- l-phenyl- i-pyrrolidinecarboxylic acid (3). To 1.70 g (10 mmol) of spiroacylal 2 was added 2.79 g (3 mmol) of aniline. The mixture became a homogeneous orange solution after 15 min and was allowed to stir at room temperature for 12 hr. The resulting crystalline mass was diluted with 150 mL of chloroform, washed three times with 10 mL of aqueous 10% hydrochloric acid, washed once with 20 mL of brine, dried (MgS04), and decolorized with a small amount of activated carbon. Concentration of the organic layer by rotary evaporation gave 5.27 g of a brown residue, which was recrystallized from chloroform-hexane to afford 4.86-5.07 g (79-82%) of the pyrrolidinone 3 as white crystals, mp 146-148°C (dec) (Note 4). 

The solution was neutralized with calcium carbonate and concentrated to 75 cc. The addition of 10 volumes of 95% ethanol precipitated granular calcium n-gluconate yield 21.5 g. after drying at 80°. The crude product was recrystallized by solution in 100 cc. of boiling water, addition of 2 g. of active carbon, concentration of the filtrate to 50 cc. and addition of a small amount of ethanol. After sixteen hours in the icebox, the crystals were filtered, washed with 50% ethanol and dried yield 20.2 g. Only 0.25 g. more was obtained from the mother liquor. The total yield of recrystallized product was 96% of theory. The rotation of the calcium n-gluconate in about 3% water solution was [a] D + 8.5°. 

Fig. 17 Enhancement factor with physical absorption of CO in aqueous solutions as a function of the activated carbon concentration in a stirred cell with O) = 1.33 s and d < 5 ym.

C. Palladium on carbon catalyst (5 per cent. Pd). Suspend 41-5 g. of nitric acid - washed activated carbon in 600 ml. of water in a 2-litre beaker and heat to 80°. Add a solution of 4 1 g. of anhydrous palladium chloride (1) in 10 ml. of concentrated hydrochloric acid and 25 ml. of water (prepared as in A), followed by 4 ml. of 37 per cent, formaldehyde solution. Stir the suspension mechanically, render it alkaUne to litmus with 30 per cent, sodium hydroxide solution and continue the stirring for a further 5 minutes. Filter off the catalyst on a Buchner funnel, wash it ten times with 125 ml. portions of water, and dry and store as in B. The yield is 46 g. 

The removal of volatile organic compounds (VOC) from air is most often accompHshed by TSA. Air streams needing treatment can be found in most chemical and manufacturing plants, especially those using solvents. At concentrations from 500 to 15,000 ppm, recovery of the VOC from steam used to regenerate activated carbon adsorbent thermally is economically justified. Concentrations above 15,000 ppm ate typically in the explosive range and... 

For brines having very low iodide concentrations, ie, in some facilities in Japan and in the former USSR, the activated carbon method of recovery is used. This method consists of a process involving the treating of the acidified brine with sodium nitrite in large tanks, where the following reaction takes place ... 

Other recovery methods have been used (10). These include leaching ores and concentrates using sodium sulfide [1313-82-2] and sodium hydroxide [1310-73-2] and subsequentiy precipitating with aluminum [7429-90-3], or by electrolysis (11). In another process, the mercury in the ore is dissolved by a sodium hypochlorite [7681-52-9] solution, the mercury-laden solution is then passed through activated carbon [7440-44-0] to absorb the mercury, and the activated carbon heated to produce mercury metal. Mercury can be extracted from cinnabar by electrooxidation (12,13). 

Decomposition with Moist Activated Carbon. The waste gas stream is passed through packed activated carbon towers where water is fed at the top of the towers. The water is normally recycled. If the hydrochloric acid concentration in the recycled water exceeds 10%, the decomposition efficiency is greatly reduced. Thus, a sufficient supply of fresh water must be assured and a hydrochloric acid stream continuously taken out (33). 

Sodium thiosulfate is a by-product of the manufacture of Sulfur Black and other sulfur dyes (qv), where organic nitro compounds are treated with a solution of sodium polysulfide to give thiosulfate. The dyes ate insoluble and ate recovered by fUtration. The fUtrate is treated with activated carbon and filteted to obtain a sodium thiosulfate solution. After concentration and crystallization, the final product assays ca 96% Na2S202 5H20 (34) (see Dyes AND... 

Both batch and continuous processes employ excess sulfur and operate at 85—110°C. Trace amounts of polysulftdes produce a yellow color which iadicates that all the ammonium sulfite has been consumed. Ammonium bisulfite is added to convert the last polysulfide to thiosulfate and the excess ammonia to ammonium sulfite. Concentrations of at least 70% (NH 2S2 3 obtained without evaporation. Excess sulfur is removed by filtration and color is improved with activated carbon treatment or sodium siUcate (66). Upon cooling the aqueous concentrated solution, ammonium thiosulfate crystallines. 

Most volatile organics adsorb on activated carbon in the Hquid state. Low concentrations of biodegradable volatiles can be removed by adsorption and biodegradation on activated carbon. 

Activated carbon generally presents no particular health hazard as defined by NIOSH (62). However, it is a nuisance and mild irritant with respect to inhalation, skin contact, eye exposure, and ingestion. On the other hand, special consideration must be given to the handling of spent carbon that may contain a concentration of toxic compounds. 

Manufacturer material safety data sheets (MSDS) indicate that the oxygen concentration in bulk storage bins or other enclosed vessels can be reduced by wet activated carbon to a level that will not support life. Therefore, self-contained air packs should be used by personnel entering enclosed vessels where activated carbon is present (68). 

Adsorption. Adsorption (qv) is an effective means of lowering the concentration of dissolved organics in effluent. Activated carbon is the most widely used and effective adsorbent for dyes (4) and, it has been extensively studied in the waste treatment of the different classes of dyes, ie, acid, direct, basic, reactive, disperse, etc (5—22). Commercial activated carbon can be prepared from lignite and bituminous coal, wood, pulp mill residue, coconut shell, and blood and have a surface area ranging from 500—1400 m /g (23). The feasibiUty of adsorption on carbon for the removal of dissolved organic pollutants has been demonstrated by adsorption isotherms (24) (see Carbon, activated carbon). Several pilot-plant and commercial-scale systems using activated carbon adsorption columns have been developed (25—27). 

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