Activated carbon phenol number

Isotherms are normally developed to evaluate the capacity of the carbon for the adsorption of different contaminants. Data are obtained in batch tests, which determine the equilibrium relationship between the compound adsorbed on the carbon and that remaining in solution. The isotherms are used as screening tools to determine which carbon is suitable for a given application. Batch equilibrium tests are often complemented by dynamic column studies to determine system size requirements, contact time, and carbon usage rates [19]. Other parameters that are used to characterize activated carbons for water treatment include phenol number, an index of the ability to remove taste and odor, and molas.ses number, which correlates with the ability to adsorb higher molecular weight substances. However, these parameters still do not reflect performance in service, and they can only be considered as guidelines. 

However, the usual tests for characterizing active carbon — such as the phenol number, the surface area (BET 2)> tl tannin index or the iodine index — are inadequate for evaluating the potential removal of the humic substances by the carbon. Moreover the resulting adsorption may differ according to the source and previous treatment of those substances and the characteristics of the feed water used. 

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

It is sometimes difficult to identily the actual cause of odor and taste problems in water. Some of common odor- and taste-causing compounds include hydrogen sulfide (H2S), methane, algae, oils, phenols, cresols, and volatile compounds. Removal of taste and odor problems is a common application for the water aeration process. The process is suitable for H2S, methane, and volatiles, but not for algae and oils, phenols, and cresols. The compounds must be volatile for aeration to be effective. Aeration is appropriate for many industrial compounds. A classic installation is at Nitro, WV, which utilizes aeration and granular activated carbon (GAC). The raw water had threshold odor numbers (T.O.N.) of 5000-6000 from industrial contamination. The process was effective for reducing the taste and odor down to levels of 10-12 T.O.N. Although taste and odor applications are most common, there are many other tastes and odors that simply cannot be removed by aeration alone, which may explain why so many early plants were abandoned (1-10). 

High surface area activated carbon fibers were first prepared by direct carbonization and activation of phenolic fibers in steam/CO2 environment at temperatures around 1000°C (Economy and Lin 1976). These activated carbon flbers, manufactured in the form of a fabric, have received increased attention as adsorbents in air treatment processes. Because these fabrics are easy to handle, there is an increasing demand for them in various applications such as protective fabrics, filtration devices, odor absorbents, and for a wide range of ancillary industrial applications. The high cost of these fabrics has limited their potential use for a number of applications. High cost is also an issue for their use in military applications (Mangun et al. 1999). 

The liquid-phase materials are usually characterized by sorption tests using phenol, iodine, or "molasses number." The vapor-phase activated carbons are usually characKiized by carbon tetrachloride or benzene adsorption tests. The adsorption capacity and the bulk density define the volumetric treatii capability of the material. 

Adsorption of phenol and its derivatives from aqueous solutions on active carbons and carbon blacks has been the subject matter of a large number of investigations. Jaroniec and coworkers,Enrique et al. Worch and Zakke, and Magne and Walker studied the adsorption of several phenols from aqueous solutions and found that the adsorption was partly physical and partly chemical in character. Aytekin, ChapUn, and Kiselev and Krasilinkov observed that the adsorption isotherms of phenol from aqueous solutions were step-wise, suggesting the possibility of rearrangement of phenol molecules in the adsorbed phase and their interaction with active sites on the carbon surface. Morris and Weber, however, found that the adsorption isotherms of phenols on active carbons show two plateaus, even... 

Puri and coworkers 45 studied the adsorption of phenol and p.nitrophenol from aqueous solutions on a number of activated carbons and carbon blacks at low and moderate concentrations, and found that the adsorption was partly reversible and partly irreversible. At moderate concentrations, there was a small irreversible adsorption when phenol concentration was 0.12 M in the case of carbons associated with greater than 1.5% oxygen, which they attributed to the complexation of n electrons of the benzene nucleus with the carbonyl groups present on the carbon surface. The irreversible adsorbed amount, however, was only 3 to 4% of the total adsorption. The adsorption isotherms of reversibly adsorbed phenol for different activated carbons, and carbon blacks (Figure 7.11) were almost similar. In the case of carbon blacks, the isotherms showed a well-defined plateau followed by a distinct rise, indicating completion of the monolayer and starting of a second layer. However, in the case of activated carbons, there was no indication for the commencement of the second layer, although the formation of the monolayer was completed at about the same concentration of the phenol solution as in the case of carbon blacks. 

Ji et al. (2010,2012) discuss a number of types of reactions of organic substances in liquid ammonia, and provide many references to recent and earlier work. They compare the equilibrium constants of phenols and carbonyl-activated carbon adds in ammonia and water, and describe work that is part of an ongoing study of the kinetics of a variety of reactions, including aromatic substitutions and solvolyses in ammonia. They point out that owing to its weakness as an add and as a hydrogen-bond donor, in many respects ammonia behaves as a dipolar aprotic solvent. It solvates cations strongly, but anions hardly at all (Marcus, 1983,1985). The low value of the autoprotolysis constant ( 10 at -33°C) is chiefly due to the weakness of ammonia as an acid. The mobility of the NH ion in liquid ammonia is not anomalous (Lagowski,... 

Pore volumes of carbons are typically of the order of 0.3 cm /g. Porosities are commonly quoted on the basis of adsorption with species such as iodine, methylene blue, benzene, carbon tetrachloride, phenol or molasses. The quantities of these substances adsorbed under different conditions give rise to parameters such as the Iodine Number, etc. Iodine, methylene blue and molasses numbers are correlated with pores in excess of 1.0,1.S and 2.8 nm, respectively. Other relevant properties of activated carbons include the kindling point (which should be over STO C to prevent excessive oxidation in the gas phase during regeneration), the ash content, the ash composition, and the pH when the carbon is in contact with water. Some typical properties of activated carbons are shown in Table 2.2. 

Phenols and their derivatives, as well as hydroquinone are used in industry for the synthesis of dyes, plastics, insecticides and pesticides most of phenols are toxic, they are pollutants of water, and are harmful for various biological processes. Among a great number of methods for removal of phenols, adsorption is the most convenient one many adsorbents, e.g. activated carbon [91] and modified bentonites [92] are known. Today the use of natural and chlorinated adsorbents for wastewater treatment is increasing due to their abundance and low cost. 

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