The use of microwave radiation for obtaining activated carbons from sawdust and their potential application in removal of NO2 and H2S

• The alternative method of utilization of sawdust coniferous wood is proposed.
• The activated carbons obtained from sawdust can be used as adsorbents.
• NO2 and H2S sorption properties largely depend on adsorption conditions.

Activated carbons obtained from sawdust pellets from coniferous wood were used as adsorbents of nitrogen dioxide and hydrogen sulphide. The precursor was subjected to pyrolysis at 400 °C in nitrogen atmosphere and next to physical activation at 600 and 700 °C by CO2. Some part of the precursor was also subjected to direct activation at 600 °C by CO2. The effect of activation temperature on the textural parameters, acid–base character of the surface and sorption properties of activated carbons was analysed. The resulting carbons were characterized by low-temperature nitrogen sorption, determination of pH and the number of surface oxygen groups by Boehm method. The adsorption of NO2 and H2S was carried out from dry or moist (70% humidity) air.The results have shown that NO2 and H2S sorption properties of activated carbons depend on the temperature of activation and the conditions of adsorption. The results obtained in our study have proved that a suitable choice of the pyrolysis and activation procedure of sawdust can give adsorbents with high capacity of nitrogen dioxide, reaching to 54.7 and 28.8 mg NO2/g in dry and wet conditions, respectively and low capacity of hydrogen sulphide of 4.1 and 6.2 mg H2S/g in dry and wet conditions, respectively.