The present work reports a theoretical study of the infrared spectra of chemical structures that are suitable to the description of the surface chemistry of carbon materials. Prior to any consideration, the computational approach was tested and adapted by comparing the predicted IR spectra to those obtained experimentally for various reference compounds. Several models were considered, subsequently accounting for the most relevant functional groups that have been postulated to decorate the edges of graphene layers on carbon materials (i.e., anhydrides, carboxyls, lactones, phenolic, quinones, and pyrones). For each of the previous functional groups, different structures involving a different number of fused rings were considered. This strategy allowed us to establish the effect of conjugation on the shift of the IR frequencies corresponding to a given functional group. Cooperative effects between different functional groups (phenol-carboxyl, phenol-lactone, and so on) were another aspect that revealed itself to be an interesting issue when assigning frequencies in the IR spectra of highly oxidized carbon materials. Thus, it was found that the frequencies of the CdO bonds present in acid functional groups were systematically lowered when phenolic groups were close enough to establish hydrogen bonds. Special attention was also paid to the elucidation of the origin of the 1600-cm -1 band of carbons. It was found that, in the case of acid carbons, this band can be assigned to CdC stretching of carbon rings decorated mainly with phenolic groups. Cyclic ethers in basic carbons would also promote absorption in the 1600-cm -1 region of the IR spectrum. Finally, the predicted assignments are employed to interpret the IR spectra obtained experimentally for several activated carbons.

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The use of sewage sludge as a precursor of adsorbent/ catalyst materials for environmental applications has been encouraged during the past few years. Due to the heterogeneous nature of sludges, there exists a lack of information regarding the characteristics of these low-cost precursors and how their physicochemical properties affect the final performance of materials prepared from them. In this work, three sewage-sludges collected at WWTPs with assorted sludge/wastewater treatment schemes were used as precursors of adsorbents/catalysts for H2S removal at room temperature. All the solidswere characterized to establish their textural properties and chemical composition, including the speciation of the adsorbents/ catalysts inorganic fraction. Thermal treatment (gasification) of the raw (dried) sludges increased the H2S removal ability in all cases. For these thermally treated materials, catalytic conversion to elemental sulfur and sulfate moieties was found to be the main route of H2S removal. Results indicate that adsorbents based on an iron/calcium-containing sludge were the most reactive and exhibited the highest capacities for H2S retention. Forthis particulartype of sludge, a reasonably good performance was observed even when the dried (raw) sludge was used as adsorbent/ catalyst. Alternatively, the oxidation of H2S by chars obtained from the other two sludges under study was related to their textural properties.