Pyrolysis of activated carbons exhausted with organic compounds

Abstract

The regeneration of activated carbons used for the decontamination of water and wastewater polluted with organic compounds related to the pharmaceutical industry, has been studied in this work. To this end, the pyrolysis of exhausted activated carbons was performed in a quartz reactor. The influence of the pyrolysis of saturated activated carbons on their adsorptive capacities and porous structure was evaluated. Textural characterisation of the samples was carried out by helium density, and N 2 and CO 2 adsorption isotherms, at À196 and 0 8C, respectively. Consecutive cycles of pyrolysis of activated carbons exhausted with phenol and salicylic acid, generated a widening of the microporosity, and a decrease in the apparent BET surface areas. The adsorptive capacities for phenol retention after a series of adsorption/ pyrolysis cycles were found to decrease drastically. In contrast, consecutive cycles gave higher salicylic acid adsorptive capacities, as compared to phenol. The DTG pyrolysis profiles of the samples saturated with salicylic acid appeared at lower temperatures than those of phenol, which showed two peaks, while those exhausted with salicylic acid only showed one. These results provide evidence of the different adsorption mechanisms of these two pollutants.

Phenol Adsorption and Photo-Oxidation on Porous Carbon/Titania Composites

“…425 ºC which was attributed to desorption of the chemisorbed fraction of phenol which showed a stronger interaction with the carbon matrix. Similar desorption profiles showing several peaks for phenol adsorption sites with different natures have been reported for activated carbons elsewhere (Ania et al 2005;Toth et al 2009). Based on the relative intensities of both peaks, it may be inferred that physisorption was favoured over chemisorption for all the composites at low solution concentrations of phenol.…”

“…The samples were further characterized by thermogravimetric analysis (Setaram Labsys) employing the following instrument settings: heating rate of 15 ºC/min; nitrogen atmosphere at a flow rate of 50 mᐉ/min. The point of zero charge was evaluated by the mass titration method as described elsewhere (Ania et al 2007). …”

Adsorption of 2,4-dichlorophenol from aqueous solution onto microwave modified activated carbon: Kinetics and equilibrium

“…Although the shapes of the isotherms were rather preserved, specific surface areas and micropore volumes slightly decreased after microwave irradiation. This behavior was reported in other literature [12] . These changes in the porous structure are attributed to internal reorganization of the carbon as a consequence of the decomposition of surface oxygen-containing groups.…”

Understanding phenol adsorption mechanisms on activated carbons

“…1). It is generally accepted that the fraction of phenol adsorbed at low temperatures corresponds to physisorption whereas the peaks at higher temperatures belong to chemisorbed species (Moreno-Castilla et al 1995;Ania et al 2005b;Castillejos-Lopez et al 2008;Toth et al 2009). In good agreement with previous works and based on our DTG data it would seem that phenol is both physi-and chemisorbed in the hydrophobic B and BOH carbons, whereas chemisorption is not detected in the oxidized carbon.…”