Activated carbons adsorption capacity

Wood GO (1992) Activated carbon adsorption capacities for vapors. Carbon 30 593-599... 

Nirmalakhandan, N.N. and Speece, R.E. (1993). Prediction of Activated Carbon Adsorption Capacities for Organic Vapors Using Quantitative Structure-Activity Relationship Methods. Environ.Sci. Technoi, 27,1512-1516. 

This section aims to give an overview of adsorption processes of metal ions by activated carbon. Three cases are detailed (1) the adsorption of metal ions onto virgin activated carbon adsorption capacities are given in static and dynamic reactors, and the influence of various operating conditions is shown (2) the adsorption of metal ions onto activated carbon preloaded with organic matter (3) the saturation of activated carbon by organic matter and metal hydroxides after its use in wastewater treatment. The influence of metal hydroxides on activated carbon regeneration is demonstrated. 

In carbon adsorption, contaminants are physically attracted or adsorbed on the surface of the carbon. Adsorption capacities are high for carbon because its porous nature provides a large surface area relative to its volume. Activated carbon is prepared from lignite, bituminous coal, coke, wood, or other organic materials such as coconut shells. 

Activated carbon has high specific surface area with respect to its volume, and thus has high adsorption capacity. Activated carbon adsorption is considered to be one of the most versatile treatment technologies and can remove classical pollutants such as COD, TOC, BOD, and nitrogen, as well as toxic pollutants such as phenol, refractory organic compounds, VOCs, and soluble heavy metals.38 Activated alumina and peat have also demonstrated similar abilities. 

B. Buczek, L. Czepirski, and J. Zietkiewicz, Improvement of hydrogen storage capacity for active carbon, Adsorption, 11, 877-880 (2005). 

Yoon et al. [61] reported a comprehensive investigation of activated carbon adsorption for the removal of 17P-estradiol, 17a-ethynyl estradiol, and bisphe-nol A (a common plasticizer). They found a range of capacities when several activated carbons were tested for removal of these compounds, and the ease of removal of the three compounds corresponded quite well to their octanol— water coefficients. Table 26.2 shows some of these results, which also suggest quite a strong effect of water quality, with water 2 having almost twice the concentration of DOC as water 1. The important conclusion for water authorities was that these compounds could be successfully removed by activated carbon. 

The influence of inlet concentration of MTBE on the performance of an activated carbon adsorption column was studied in three references [27,34,55]. The authors found that the influent concentration of MTBE shows a strong correlation with capacity, a higher concentration resulting in a higher carbon loading [27,34]. The carbon usage rate was found to increase with the inlet concentration [34,55]. 

Figure 6.13 Catalytic activity and adsorption capacity of activated carbons in the CWAO process of aqueous ammonia. C, original AC COX, C oxidized with HNO3 CH, C treated with H2 at 673 K CHO, CH oxidized with HNO3 COH, COX treated with H2 at 673 K. (Adapted from ref. 207.)...

Activated carbons for pesticide adsorption were prepared from the char of GRT granules (Betancur et al., 2009). The required surface porosity and desired functional groups on the surface of the activated carbon were achieved by a combination of chemical and physical treatment of tire char prior to physical activation. The adsorption capacity of the carbons was evaluated for pesticide removal from waste water. A cost analysis of the prepared adsorbents indicated that they are more cost effective and efficient than the most commercial adsorbents available for removal of pesticides from waste water. 

Adsorption is an exothermic process. The adsorption enthalpy, decreases as the load of adsorbed molecules increases. In activated carbon adsorption systems for solvent recovery, the liberated adsorption enthalpy normally amounts to 1.5 times the evaporation enthalpy at the standard working capacities which can result in a 20 K or more temperature increase. In the process, exothermic adsorption mechanisms may coincide with endothermic desorption mechanisms. ... 

Buczek, B., and Czepirski, L., Improvement of capacity for active carbons, Adsorpt. Sci. Technol., 4(4), 217-223... 

It is well known that both the adsorbate and the adsorbent properties play a very important role in activated carbon adsorption. Adsorption is a manifestation of complicated interactions among the three components involved, that is, the adsorbent, the adsorbate, and the solvent. Normally, the affinity between the adsorbent and the adsorbate is the main interaction force controlling adsorption. However, the affinity between the adsorbate and the solvent (i.e., solubility) can also play a major role in adsorption. Hydrophobic componnds have low solubility and tend to be pushed to the adsorbent surface and hence are more adsorbable than hydrophilic compounds. Meanwhile, we know that phenolic compounds with different fnnctional groups can lead to different solubility, which may lead to different oligomerization extent. Therefore, the adsorption behavior of phenolic componnds with different fnnctional gronps has to be nnderstood. As illustration, we consider the interpretation of experimental isotherms by Ln and Serial (2007) for the adsorptive capacity of five different phenolics on GAC F400 and two ACFs, ACC-10 and ACC-15, under both anoxic and oxic conditions (Fignre 6.2). 

Determination of Adsorptive Capacity of Carbon by Isotherm Technique Determining Operating Performance of Granular Activated Carbon... 

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