Activated carbon method

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 ... 

ISO 176, Plastics - Determination of loss of plasticizers - Activated carbon method, 1976. 

Requires lower materials costs than other activated carbon methods. 

P prowicz J., Skoczkowski K., Watfga E. PN-82/C—97555.06. Activated carbon. Method of test. Determination of phenol number. 

BS 2782. Method 465A and B. Determination of los.s of plasticizers (activated carbon method). 1979. 

ASTM D120.1. Volatile los.s from plastics using activated carbon methods. 1994. 

A direct activated carbon method is specified for determination of volatiles loss of calendered, extruded, and cast films and sheeting. The standard also contains a graph of maximum volatile loss vs. film thickness. 

ASTM D1203-94(1999) Standard Test Methods for Volatile Loss From Plastics Using Activated Carbon Methods... 

PN-93/C-89291.29 Plastics - PVC resins for general use - Determination of hot plasticizer absorption PN-EN ISO 176 2002 (U) Plastics - Determination of loss of plasticizers - Activated carbon method (ISO 176 1976)... 

Adsorption. Some organics are not removed in biological systems operating under normal conditions. Removal of residual organics can be achieved by adsorption. Both activated carbon and synthetic resins are used. As described earlier under pretreatment methods, regeneration of the activated carbon in a furnace can cause carbon losses of perhaps 5 to 10 percent. 

The catalyst is also employed in the form of the finely-divided metal deposited upon activated carbon (usually containing 5 or 10 per cent. Pd) two methods of preparation are described, in one reduction is effected with alkaline formaldehyde solution and in the other with hydrogen ... 

Regardless of method, desorption is never complete. Adsorbent capacity is always less following regeneration than it is on initial loading of adsorbent. Some adsorbable materials undergo chemisorption they chemically combine with the adsorbent. An example is the Reinluft process (52) for removing SO2 from flue gas on activated carbon. The SO2 is attached to the carbon as sulfuric acid. Desorption occurs only upon heating to 370°C a mixture of CO2, evolved from the chemically bound carbon, and SO2 are driven off. 

Another dynamic iastmment, the Scentometer, is the basis for odor regulations ia the states of Colorado, Illinois, Kentucky, Missouri, Nevada, and Wyoming, and ia the District of Columbia (324). The portable Scentometer (Bameby-Cheney) can produce dilution ratios up to 128 1 ia the field. The Scentometer blends two air streams, one of which has been deodorized with activated carbon. The dilution ratio is decreased until the odor becomes detectable (325). Improvements to dynamic methods have been recommended (326). 

A wide range and a number of purification steps are required to make available hydrogen/synthesis gas having the desired purity that depends on use. Technology is available in many forms and combinations for specific hydrogen purification requirements. Methods include physical and chemical treatments (solvent scmbbing) low temperature (cryogenic) systems adsorption on soHds, such as active carbon, metal oxides, and molecular sieves, and various membrane systems. Composition of the raw gas and the amount of impurities that can be tolerated in the product determine the selection of the most suitable process. 

Other methods suggested for H2 purification include adsorption and desorption on active carbon and fractional crystalliza tion (qv) of impurities fromhquid hydrogen. Centrifuging at 1—5.1 MPa (10—50 atm) and 64—110 K while keeping the temperature below the dew point of impurities that collect as a hquid film in the centrifuge has also been suggested. Purities over 99% can be obtained by this method (192). 

Quantitative Analysis of All llithium Initiator Solutions. Solutions of alkyUithium compounds frequentiy show turbidity associated with the formation of lithium alkoxides by oxidation reactions or lithium hydroxide by reaction with moisture. Although these species contribute to the total basicity of the solution as determined by simple acid titration, they do not react with allyhc and henzylic chlorides or ethylene dibromide rapidly in ether solvents. This difference is the basis for the double titration method of determining the amount of active carbon-bound lithium reagent in a given sample (55,56). Thus the amount of carbon-bound lithium is calculated from the difference between the total amount of base determined by acid titration and the amount of base remaining after the solution reacts with either benzyl chloride, allyl chloride, or ethylene dibromide. 

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). 

Waste Disposal. Because of its low Boiling poiat and high, toxicity, measures must be taken to prevent the entrance of phosgene iato drains or sewers. If recycle of phosgene is not feasible, phosgene waste can be handled by one of the decomposition methods mentioned above, ie, caustic scmbbiag, moist activated carbon towers, or combustion. 

Another method employed is the treatment of aqueous solutions of aminophenols with activated carbon (81,82). During this procedure, sodium sulfite, sodium dithionite, or disodium ethylenediaminotetraacetate (82) is added to increase the quaUty and stabiUty of the products and to chelate heavy-metal ions that would catalyze oxidation. Addition of sodium dithionite, hydrazine (82), or sodium hydrosulfite (83) also is recommended during precipitation or crystallization of aminophenols. 

Activated carbon adsorption generally uneconomical for removal of >1000 ppm contaminant from large stream unless bed regenerated steaming often easiest regeneration method but creates new wastewater problem usually 3—5 kg steam requited per kg of carbon for regeneration. 

Methods of Purification. Although carbon dioxide produced and recovered by the methods outlined above has a high purity, it may contain traces of hydrogen sulfide and sulfur dioxide, which cause a slight odor or taste. The fermentation gas recovery processes include a purification stage, but carbon dioxide recovered by other methods must be further purified before it is acceptable for beverage, dry ice, or other uses. The most commonly used purification methods are treatments with potassium permanganate, potassium dichromate, or active carbon. 

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