Thermal treatment of wood, bark and leaves of same poplar tree through hydrothermal carbonization and activation: Roles of aliphatic structures in pore development

Wood, bark and leaves are indispensable components of forestry biomass, varied biological composition of which might not only form hydrochar of varied nature but also activated carbon (AC) of distinct pore characteristics. This was investigated herein by hydrothermal carbonization (HTC) of wood, bark and leaves of same poplar tree at 260(degrees)C and subsequent activation with K2C2O4 at 750 C-degrees. The results indicated that organics in leaves were thermally unstable and fragmentation reactions dominated in HTC, producing hydrochar of much lower yield than that from HTC of cellulose/hemicellulose-rich wood and bark. Furthermore, the oxygen -rich hydrocharleaves showed not only lower thermal stability than that of hydrochar-wood/bark, but also produced remarkably less AC in activation. The hydrolysis of sugary structures in especially wood and followed polymerization of the intermediates enhanced aromatic degree and resistivity of hydrochar towards cracking, increasing AC production but preventing development of porous structures. Hence, the AC -wood showed the lowest specific surface area (1315.2 m(2)/g). In converse, the highly unstable nature of hydrochar-leaves facilitated generation of mesopores (1038.9 m(2)/g) and also some macropores, achieving total specific surface area of 1843.8 m(2)/g. The abundance of cellulose/hemicellulose together with extractives and inorganics in bark formed AC -bark with highest specific surface area (2213.2 m(2)/g) and also most abundant micropores (1941.4 m2/g), rendering its superior capability for adsorption of tetracycline (680.3 mg/g).