Active carbons from waste biochars

Studies of preparation of active carbons of good structural and adsorption properties based on commercial biochars, which become wastes after removal of precious volatile components from natural raw materials of different origin, i.e., from wheat straw, Miscanthus grass, walnut shells, and energetic willow were carried out. There was applied the physical activation under atmospheric pressure in the fluidal reactor using CO2 or overheated steam and in the closed system in the high pressure microwave reactor under hydrothermal conditions. The obtained active carbons were investigated by means of adsorption (N2), thermal (TG, DTG, DTA), spectral (Raman spectra) as well as electron microscopy methods. The adsorbents obtained as a result of modification were characterized by a well-developed porous structure and greater thermal resistance compared to the initial biochars.