Preparation of activated carbon from pine sawdust with hydrothermal-pressure preconditioning

Abstract

The aim of this paper has been to find a biomass pretreatment protocol for preparing activated carbons without using any of the commercially-applied chemical additives. Instead, we employed a hydrothermal-pressure preconditioning protocol (160 ℃, 300–390 psi) to induce rapid steam expansion within pine sawdust, followed by pyrolysis/activation. The pinewood sawdust was preconditioned via three alternative synthesis protocols: (a) High-Pressure Hydrothermal Eruption (HPE), (b) High-Pressure Hydrothermal (HP), and (c) non-pre-pressure Hydrothermal (HY) treatment. Activated carbons were characterized by BET, SEM, FTIR and XPS; and the results indicate that HP achieved the highest specific surface area (990 m2 g−1) and micropore volume (0.344 cm3 g−1). Adsorption tests with perfluorooctanoic acid (PFOA) and methylene blue (MB) show that the adsorption capacities of the prepared activated carbons were significantly better than a commercial activated carbon (CAC). The HP exhibited the highest adsorption capacity for PFOA (232 mg g−1) and MB (350 mg g−1). The PFOA adsorption rates were empirically described by pseudo-second-order and intra-particle diffusion models; and the equilibrium sorption of PFOA fit well to Langmuir isotherm model.