Activated carbons have both hydrophilic surface oxygen functional groups, which act as primary adsorption centers for water vapor and hydrophobic graphene layers on which non-polar species are primarily adsorbed. The aim of this research was to investigate the effects of oxygen surface functional groups, in activated carbons, on the adsorption characteristics of water vapor. Activated carbon G, was oxidized using nitric acid and then heat treated in the range 387-894 K to produce a suite of adsorbents with varying oxygen contents in the range 0•4-21•5 %, but very similar porous structure characteristics, thereby minimizing effects due to changes in porous structure. The type and concentration of surface oxygen groups present on each sample was assessed using TPD, FTIR and Boehm titration methods. Water vapor adsorption at low relative pressure was dramatically enhanced by the presence of functional groups, in particular, carboxylic groups. Kinetic profiles for each pressure increment were modeled using a set of nested kinetic models, which allow the adsorption kinetics to be interpreted in relation to the adsorption mechanism. The results establish a clear relationship between water adsorption kinetics and the type and concentration of oxygen surface functional groups. A linear relationship was observed between the rate constants in the low pressure region and the inverse of the Henry's Law constant. This indicates the importance of adsorbate-adsorbent interactions in water adsorption kinetics and is consistent with a site-to-site hopping mechanism between functional groups.

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A procedure for preconcentration of Mn(II), Fe(II), Co(II), Cu(II), Cd(II), Zn(II), Pb(II) and Ni(II) based on retention of their complexes with 8-hydroxyquinoline (HQ) on Amberlite XAD-2000 resin in a column was proposed for the analysis of environmental samples by flame AAS. Various parameters such as pH, eluent type, volume, concentration, flow rate and volume of sample solution, and matrix interference effect on the retention of the metal ions were investigated. The optimum pHs for the retention of metal complexes in question were about 6 except for Mn 2＋ for whose value is 8. The loading capacity of the adsorbent for these metals and their recoveries from the resin under the optimum conditions were in the range 6.82-9.26 mg•g -1 and 95%-101%, respectively. The enrichment factor was calculated as 100 and the limit of detection was in the range 0.3-2.2 µg•L -1 (n＝20, blank＋ 3s). The proposed enrichment method was applied to tap water, stream water and vegetable samples. The validation of the procedure was carried out by analysis of certified reference material and standard addition. The analytes were determined with a relative standard deviation lower than 6% in all samples.

Polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran species are classes of extremely toxic compounds generated in very low concentrations in postcombustion gases and these may be removed by adsorption on porous carbons. Their extreme toxicity and very low volatility prevent detailed study of their adsorption characteristics, and therefore, models for dioxins have been used in this study. Chlorobenzene, 2-chlorotoluene, 1,3-dichlorobenzene, and 2-chloroanisole were used as models to investigate factors influencing the adsorption characteristics of dioxins on porous carbons. Adsorption studies were carried out under conditions of very low concentration and temperatures up to 453 K, which simulate those found in dioxin abatement systems. Adsorption of 2-chloroanisole on three carbons with various micro/ mesoporous structures showed that microporous structure was a critical adsorbent characteristic under these conditions. A microporous activated carbon was selected for detailed thermodynamic and kinetic studies of adsorption of chloroaromatic species in relation to adsorbate structure and adsorbent surface functional groups. Virial equation analysis of adsorption isotherms was used to determine the Henry's Law constants and isosteric enthalpies of adsorption at zero surface coverage to compare adsorbate-adsorbent interactions. The van't Hoff equation was used to determine the enthalpy of adsorption as a function of surface coverage. The role of surface functional groups on adsorption thermodynamics was investigated by oxidizing and reducing the carbon in nitric acid and hydrogen, respectively. The important factor influencing adsorption at very low concentrations is the adsorbate adsorbent interaction. Oxidation of the carbon adsorbent only has a small effect on the isosteric enthalpy of adsorption. The adsorption kinetics for each isotherm pressure increment were described by the stretched exponential equation. The activation energies and enthalpies of activation were calculated as a function of surface coverage for adsorption kinetics of chloroaromatic species. The planar molecules studied had lower activation energies and enthalpies of activation than isosteric enthalpy of adsorption indicating that a site-to-site surface hopping mechanism is the main factor in determining the adsorption kinetics. In comparison, 2-chloroanisole is nonplanar with a methoxy group giving rise to a larger minimum cross-section size and higher barrier to diffusion than isosteric enthalpy of adsorption at low surface coverage leading to the adsorption kinetics being mainly determined by diffusion through constrictions in the porous structure under these conditions. The isosteric enthalpies of adsorption initially increase with increasing surface coverage and this is attributed to π-π interactions of planar aromatic molecules confined in microporosity. The trends in the kinetic barriers and isosteric enthalpies of adsorption with surface coverage for 2-chlorotoluene are similar irrespective of adsorbent oxidation/reduction,...