Carbonaceous Materials Obtained from Sewage Sludge for $NO_2$ Removal under Wet Conditions at Room Temperature

The effect of the processes of carbonisation and activation on adsorbents obtained from sewage sludge and their sorption properties towards $NO_2$ were studied. Carbonaceous adsorbents were obtained by carbonisation of sewage sludge at 600°C for four different times 30, 60, 90 and 120 min followed by activation of the carbonisates by $CO_2$ at 800°C for 60 min. Adsorption of $NO_2$ was carried out in wet air. It has been shown that by appropriate thermal and chemical treatment of sludge, mesoporous adsorbents capable of $NO_2$ removal can be obtained. The sorption abilities of the carbonised and activated samples to adsorb $NO_2$ have been shown to increase with increased time of carbonisation and reach maximum for the carbonisation maintained for 90 min. Further increase in this time causes a decrease in the adsorption abilities of the samples. The sorption properties of the carbonisates have been proved to be determined by the chemical character of the surface, while those of the activated samples - by the porous structure.