Activated Carbon Adsorption Applications

Brasquet, C. and Le Cloirec, P., Adsorption onto activated carbon fibers Application to water and air treatments, Carbon, 1997, 35(9), 1307 1313. 

Adsorption — An important physico-chemical phenomenon used in treatment of hazardous wastes or in predicting the behavior of hazardous materials in natural systems is adsorption. Adsorption is the concentration or accumulation of substances at a surface or interface between media. Hazardous materials are often removed from water or air by adsorption onto activated carbon. Adsorption of organic hazardous materials onto soils or sediments is an important factor affecting their mobility in the environment. Adsorption may be predicted by use of a number of equations most commonly relating the concentration of a chemical at the surface or interface to the concentration in air or in solution, at equilibrium. These equations may be solved graphically using laboratory data to plot "isotherms." The most common application of adsorption is for the removal of organic compounds from water by activated carbon. 

Engineering Considerations To effect the good engineering design of an activated carbon adsorption system, it is first necessary to obtain information on the following the actual cubic feet per minute (ACFM) of air to be processed by the adsorber, the temperature of gas stream, the material(s) to be absorbed, the concentration of the material to be adsorbed, and if the intended application is air pollution control such as odor control - then the odor threshold of the material to be adsorbed. In addition, data is needed on the presence of other constituents in the gas stream, and whether or not solvent recovery is economical. 

There are several potential treatment technologies that may be applicable, but are more expensive than the methods currently used. These potential treatments include sulfide precipitation, ultrafiltration, reverse osmosis, deep-well disposal, activated carbon adsorption or activated alumina adsorption, solidification, or ion exchange.19-21... 

Adsorption Equilibrium Numerous purification and recovery processes for gases and liquids Activated carbon-based applications Desiccation using silica gels, aluminas, and zeolites Oxygen from air by PSA using LiX and 5A zeolites... 

Activated carbon adsorption is mainly a waste concentration method. The exhausted carbon must be regenerated or disposed of as hazardous waste. For GAC consumptions larger than 2000 Ib/day, onsite regeneration may be economically justified [7]. Thermal regeneration is the most common method for GAC reactivation, although other methods such as washing the exhausted GAC with acid, alkaline, solvent, or steam are sometimes practiced for specific applications [17]. 

A report on the biomedical application of activated carbon adsorption [600] is also revealing. The authors analyzed the uptakes of an aromatic compound, acetaminophen (active ingredient in Tylenol, pKj = 9.5), and an aliphatic one, (V-acetylcysteine (which provides a protective effect against acetaminophen overdose pKa = 3.3), under both gastric (pH = 1.2) and intestinal (pH = 7.0) conditions. Their results are reproduced in Table 24. 

Contemporary issues and developments relating to the application of activated carbon adsorption processes for water and wastewater treatment are discussed. Consideration is given to the increasingly important role of adsorption as a technology for removing specific target compounds or classes of compounds from waters and wastewaters... 

Activated carbon adsorption thus had early and significant origins in the field of water treatment. It is ironic, however, that most of the firm science relating to this technology was to emerge from the newer and more cliellenging application of adsorption to municipal and industrial waste treatment. This paper traces development of the activated carbon adsorption process in these several... 

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