| Recently, porous biomorphic carbon material controllably synthesized from biomass is becoming a hot spot because biomass possesses complex hierarchical structures, developed pore structures and ordered pore systems. This paper is focused on how to obtain integrated biomorphic porous carbon materials from a controllably carbonization process in the atmosphere of nitrogen and to modify the as-prepared porous carbons with nitric acid.Firstly, the effects of carbonization temperature on the micro-morphology and structure of pine-shoot were studied. Gas-evolutions in the carbonization of pine-shoot were investigated by using a TG-DTG instrument and analyzed by using a online automatic sampling GC-TCD/FID equipments. The results show that peak temperatures of gas-evolutions in the inner parts of pine-shoot are always higher than that at surface counterparts due to the heat- and mass- transfer. The morphology and structure of porous carbons were strongly influenced by carbonization temperatures. High carbonization temperature favors the decomposition of biomass and the formation of pore structures. However, extremely high carbonization temperature will plug the orifices, distort channels and destroy pore systems of biomass porous carbon. In addition, high temperature promotes the growth of graphite deposits and the formation of the honeycomb like structure with six or more angles. Even at same carbonization temperature, biomass may obtain varied pore distributions from surface to the inner.Secondly, the effects of acid concentrations on the biomorphic and structure of the porous carbons which were modified by nitric acid were also studied. The results show that debris left in porous carbon channels could be effectively removed by dilute nitric acid. Porous carbon structures could be cleaned promptly. Biomass debris is decreased, reduced, cleaning the pore structure and lessening the depth of pore-wall with the increase on the concentration of nitric acid. High concentration nitric acid is beneficial to form penetrated holes within the pore-walls. Strong nitric acid will damage porous structure by oxidizing the pore-walls, resulting in the collapse of pore systems and channels. IR results suggested that strong nitric acid can increase the number of functional groups on the surface of porous carbon.Finally, the effects of carbonization temperature and nitric acid treatment on the adsorption ability of biomass porous carbons were studied. The results show that the adsorption capacity of thiophene, iodine and methylene blue on porous carbon is enhanced with the increase of the carbonization temperature. Porous carbon with a carbonization temperature of 800 shows best adsorption capacity. Comparing with the unmodified porous carbon, porous carbon treated with nitric acid is disadvantaged to the adsorption of thiophene and iodine molecules on the porous carbon. However, porous carbon treated with strong nitric acid favors the adsorption of benzothiophene, di-benzothiophenes and methylene blue on porous carbon. The adsorption capacity of corresponding adsorbents on nitric-acid-modified porous carbon was 2.5 times, 1.6 times and 2 times, respectively, to that on unmodified porous carbon. |
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