Chemical treatment with activated carbon

Sulfolene (butadiene cyclic sulfone), m.p. 64-66°, from Shell Chemical Co., or from Aldrich Chemical Co., was found satisfactory for use as received. One lot purchased from another source required solution in hot methanol and treatment with activated carbon (250 ml. of methanol and 2 g. of Norit per 100 g. of material), filtration, and crystallization to free it of color, odor, and particulate matter. 

Pretreatment with carbon of a material to be purified often enables a chemical agent to function more effectively (Table 4 13). 2,3 In a process to reclaim iodides from petroleum brine, the initial step consisted of oxidizing the iodides to elemental iodine, and this reaction had been prevented by impurities in the brine that acted as inhibitors of oxidation. It became necessary to remove these inhibitors by pretreating the brine with a special type of activated carbon, after which the oxidation proceeded without difficulty. A similar type of behavior probably explains why hydrogen peroxide is a more effective bleaching agent for certain waxes after they have been given prior treatment with activated carbon. 

The water that evaporates from the dechlorinated brine is condensed in a cooler. The condensate, which may be chemically dechlorinated, is returned to the brine circulation system if necessary to maintain the volume of the brine circuit. If necessary, the remaining chlorine content can be further reduced by blowing with compressed air, by a second vacuum treatment, by treatment with activated carbon (63], or by chemical treatment with hydrogen sulfite, thiosulfate, sulfur dioxide, or sodium hydrogensulfide. 

Adsorption This is the most widely used of the physical-chemical treatment processes. It is used primarily for the removal of soluble organics with activated carbon serving as the adsorbent. Most liquid-phase-activated carbon adsorption reactions follow a Freundlich Isotherm [Eq. (25-21)]. 

The activated carbons have been prepared by carbonization of precursors, i.e., raw materials with subsequent activation by physical treatment and/or chemical treatment. The activation procedure is conducted in order to enlarge the volume and size of the pores which were already created during the carbonization process and to create some new porosity. Most commonly employed activation methods are divided into physical and chemical activations.14"16,18"35... 

The purification of inorganic chemicals with activated carbon is not common practice. Usually it is more practical to procure source materials that do not require such purification. For the most part, applications in this field are limited to the treatment of waste materials containing impurities that are difficult to separate by other methods. Carbon performs a dual task of recovering a product and at the same time eliminating a disposal problem. 

Thermal and chemical regeneration of activated carbons exhausted with various aromatic compounds have been compared [76]. Whereas thermal treatment is independent on the characteristics of the adsorbate, the efficiency of the chemical treatment, which varies from 15.2 to 96.8 %, is a function of the properties of adsorbate and the choice of chemical... 

The first step in the treatment process usually is the chlorination of the solution to ensure oxidation of all the mercury. This may be carried out at pH 3 to avoid the precipitation of iron. After filtration to remove undissolved mercury and hydroxides of other metals, the effluent goes on to final treatment. In order to protect the easily oxidized thiol groups, reduction of free chlorine is necessary. This is usually done in two steps, chemical treatment with a reducing agent and chemisorption on activated carbon (both in Section 7.S.9.3). The reducing agent in mercury-removal plants is commonly an -based species. 

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